30
Large Intestine
Jessica Cohan, MD
Madhulika G. Varma, MD
ANATOMY
The colon begins at the ileocecal valve and ends at the rectum, spanning 140 cm (5 feet) in length. The colon has both intraperitoneal and retroperitoneal components. The cecum, ascending, and descending colon are retroperitoneal, whereas the transverse colon and sigmoid are intraperitoneal (Figure 30–1). The diameter of the lumen is greatest at the cecum (~ 7 cm), and decreases distally. As a result, mass lesions of the cecum are least likely to cause obstruction and the thin wall of the cecum is most vulnerable to ischemic necrosis and perforation from large bowel obstructions. There are four layers of the wall—mucosa, submucosa, muscularis propria, and serosa (Figure 30–2). The mucosa is composed of three layers—a simple columnar epithelium organized to form crypts, lamina propria, and muscularis mucosa. The submucosa is the strength layer of the colon because it has the highest concentration of collagen. Therefore, this layer is especially important to incorporate during anastomoses. The muscularis propria is composed of an inner circular layer and an outer longitudinal layer that thickens into three bands around the circumference to form the taeniae coli. The appendix can be found at the point on the cecum where the taeniae converge. At the rectosigmoid, these bands fan out to form a uniform layer, marking the end of the colon and the beginning of the rectum. The forces of these muscular components of the wall result in shortening of the colon to form sacculations called haustra (Figure 30–3). These are not fixed structures, but can be observed to move longitudinally. The appendices epiploicae are fatty appendages on the serosal surface.
Figure 30–1. The large intestine: anatomic divisions and blood supply. The veins are shown in black. The insert shows the usual configuration of the colon.
Figure 30–2. Cross-section of colon. The longitudinal muscle encircles the colon but is thickened in the region of the taeniae coli.
Figure 30–3. Barium enema of normal colon. Note the appearance of haustra and the location of the splenic and hepatic flexures.
The rectum begins at the sacral promontory and ends at the anorectal ring. It lies between the colon and the anus and is 12-16 cm in length. There are no taeniae as the longitudinal muscle fans out and encompasses the circumference of the rectal wall. The rectum can be further differentiated from the colon by its lack of appendices epiploicae and haustra. The rectum is both an intra- and extraperitoneal organ. Posteriorly, the rectum is only intraperitoneal at the level of the rectosigmoid. However, the anterior and lateral walls of the upper rectum are intraperitoneal. The anterior peritoneal reflection extends low into the pelvis, approximately 5-8 cm above the anal verge and lies between the rectum and the bladder in men and uterus in women (the Pouch of Douglas). Tumors or abscesses in this location can be palpated on digital rectal or vaginal examination. Denonvilliers fascia envelops the anterior wall of the rectum. Beyond the anterior peritoneal reflection lie the seminal vesicles and prostate gland in men. In women, the cervix and rectovaginal septum lie anteriorly and the adnexa anterolaterally. The rectum has three major mucosal folds called the valves of Houston. They are variable in location, but classically occur every 3-4 cm. The superior and inferior folds are on the left and the middle fold is on the right. The middle fold marks the distal extent of the intraperitoneal rectum.
The pelvic floor is made of three muscles—the pubococcygeus, iliococcygeus, and puborectalis collectively known as the levator ani. The puborectalis forms a sling at the anorectal junction and is an important component of continence and the defecation mechanism.
Blood Supply & Lymphatic Drainage
The arterial supply of the colon is dictated by its embryological origin. The foregut, which extends to the distal transverse colon, is supplied by the superior mesenteric artery (SMA) through the ileocolic, right colic, and middle colic arteries. The hindgut, which includes the distal transverse colon to the rectum, is supplied by the inferior mesenteric artery (IMA). This gives off the left colic, 2-6 sigmoid branches, and terminates as the superior rectal (hemorrhoidal) artery. The middle and inferior rectal (hemorrhoidal) arteries originate from the internal iliac artery. There is redundancy in the arterial circulation via the meandering mesenteric artery (Arc of Riolan) as well as the marginal artery of Drummond, which is a network of arterial branches that runs the length of the colon approximately 2.5 cm from the bowel wall. The vasa recta are the terminal arteries arising from the marginal artery. These penetrate the colon wall in multiple areas on the mesenteric side, creating focal areas of weakness that have the potential to form false diverticula. The left colic, sigmoid, and superior rectal branches also originate from the IMA in a variable pattern. The venous drainage generally follows the arterial supply with the exception of the inferior mesenteric vein, which runs lateral to the ligament of Treitz to join the splenic vein. The vascular supply too is highly variable, and “normal” anatomy is found in only 15% of individuals.
The lymphatics drain via continuous plexuses in the submucosal and subserosal layers of the bowel wall. These continue on to the mesenteric lymphatic channels and nodes that accompany the blood vessels, which explain why standard planning for oncologic resections of the colon and rectum is based on the vascular supply.
Nerve Supply
The nerve supply to the colon and rectum is autonomic and, like the blood supply, is divided according to embryologic development. Sympathetic nerves to the midgut, including the right and proximal transverse colon, originate in T6-12. These synapse in the superior mesenteric plexus and then follow the SMA and its branches to the right colon. The vagus nerve provides parasympathetic fibers to the midgut. Sympathetic innervation to the hindgut (distal transverse colon to the rectum) arises from L1-3. These sympathetic fibers synapse in the preaortic plexus and then follow the IMA to the bowel wall. Nervous impulses to the bowel wall synapse in the myenteric (Auerbach’s) plexus and submucosal (Meissner’s) plexus. The myenteric plexus is located in between the circular and longitudinal layers of smooth muscle and is responsible for coordinating motility. The submucosal plexus (Meissner’s plexus) is located in the submucosa and regulates secretions, blood flow, and absorption.
The distal rectum and anus is innervated by the hypogastric nerves and the nervi erigentes. The hypogastric nerves are sympathetic fibers that originate from L1-3. These fibers course over the sacral promontory to the hypogastric plexus and form the paired hypogastric nerves near the root of the IMA. The parasympathetic fibers run in the nervi erigentes, which arise from S2-4 and join the hypogastric nerves near the lateral rectal stalks. The fibers continue anterior and laterally to innervate the rectum, pelvic floor muscles, and bladder, as well as the prostate and seminal vesicles in men. The location of these nerves makes them prone to injury during protectomy. The superior hypogastric plexus is at risk during high ligation of the IMA, the hypogastric nerves are at risk during retrorectal dissection, the inferior hypogastric plexus and nervi erigentes are at risk during mobilization of the lateral stalks, and the periprostatic plexus is at risk during dissection of Denonvillier fascia. Injury to these nerves during proctectomy can cause bladder and sexual dysfunction that is a significant source of postoperative morbidity.
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Sakorafas GH, Zouros E, Peros G. Applied vascular anatomy of the colon and rectum: clinical implications for the surgical oncologist. Surg Oncol 2006 Dec;15(4):243-255.
PHYSIOLOGY
The primary functions of the colon are absorption, secretion, motility, and intraluminal digestion. These interrelated processes are responsible for converting ileal effluent into semisolid feces. The rectum functions as a capacitance organ, storing feces produced by the colon and allowing defecation at a convenient time. When surgery or disease results in loss of colonic function, there is a significant increase in intestinal losses of water and electrolytes. If the rectum is overloaded by large volume watery stool or its capacity to distend is lost or impaired by surgery or disease, fecal urgency and frequency are noted.
Intestinal Gas
Normal volume and composition of intestinal gas has great variation amongst individuals depending on air swallowing, diet, and the composition of the microbial flora. Small amounts of intestinal gas are absorbed through the bowel wall and excreted through the lungs, but the majority (~ 400-1200 mL/d) is discharged as flatus.
Intestinal gas is comprised of nitrogen, oxygen, carbon dioxide, hydrogen, methane, and trace substances such as methyl sulfide, hydrogen sulfide, indole, and skatole. By far, the largest component is nitrogen, which makes up 30%-90% of intestinal gas. Most nitrogen comes from swallowed air, but some also diffuses from the plasma. Fermentation of nonabsorbed carbohydrates such as fiber is responsible for most of the hydrogen and carbon dioxide in gas. In lactase deficient individuals, lactose fermentation contributes as well. Methane is produced by specific hydrogen reducing bacteria (Methanobrevibacter smithii) and is only present in 30% of people. Both methane and hydrogen gases are explosive and require caution when using cautery in the bowel lumen.
Patients reporting crampy abdominal pain, bloating, and increased flatus may be suffering from increased gas production. Overproduction may be a result of a malabsorptive state and eliminating lactose, legumes, and/or wheat in the diet may be of help.
Absorption & Secretion
The colon is primarily an absorptive organ. The absorptive capacity is greatest in the cecum and ascending colon and decreases distally. Most nutrients are absorbed in the small bowel; however, when enteric contents reach the colon, they are still rich in water, electrolytes, and some nutrients. Approximately 1-2 L of ileal effluent containing 250 mEq of sodium reaches the cecum every 24 hours. The passive absorption of water and active transportation of sodium allows recovery of more than 90% of the water and sodium content. Every 24 hours, approximately 100-200 mL of water and 2-5 mEq of sodium are excreted in the feces. Table 30–1 gives average values for the composition of ileal effluent and feces. Normal feces are composed of 70% water and 30% solids. Bacteria constitute over half of the solid component. The remaining solids are food waste and desquamated epithelium. Although the absorptive capacity of the colon serves an important role in maintaining homeostasis, it is not essential to life.
Table 30-1. Mean values for electrolyte and water balance in the normal colon. A plus (+) sign indicates absorption from the colonic lumen; a minus (−) sign indicates secretion into the lumen.
This effluent also contains small amounts of nutrients which are absorbed by the colon including fatty acids, amino acids, and vitamin K. Approximately 10% of undigested starch reaches the colon where colonic bacteria fermentation produces short chain fatty acids, which are important both systemically and as a nutrient source for colonocytes.
In addition, the colon is part of the enterohepatic circulation. Bile acids not absorbed in the terminal ileum are passively absorbed in the colon. When this capacity is exceeded, the remaining bile acids are metabolized by colonic bacteria into urobilin and stercobilin. Urobilin, stercobilin, and their metabolites are responsible for giving stool its brown color.
The colon also serves an important secretory function. It secretes hydrogen, bicarbonate, chloride, and potassium ions. The colon is in communication with the circulation and is able to adjust over a wide range as needed. Pathologic states such as inflammatory bowel disease (IBD), shigellosis, cystic fibrosis, and collagenous colitis cause electrolyte and acid-base disturbances by altering colonic secretion.
Motility
Colonic motility serves to maximize absorption and move feces distally in preparation for excretion. There are numerous types of motility and these occur with great variation along the length of the colon. Normal movements are slow, variable, and complex and result in nonorganized flow of the fecal stream. In patients with normal bowel function, enteric contents reach the cecum 4 hours after a meal and the rectosigmoid by 24 hours. However, portions of the fecal stream are mixed so that new effluent may bypass old effluent, and residue from a single meal may pass in bowel movements over 3-4 days.
The enteric nervous system coordinates motility. It is increased by physical activity, stress, and diets high in fiber. In addition, the act of eating stimulates colonic transit. The gastrocolic reflex refers to the activation of colonic motor activity in response to a meal. The magnitude is determined by the fat and caloric composition. This increased activity increases ileal and colonic emptying, causing an urge to defecate.
The colon has three distinct patterns of activity that are under control of the enteric nervous system and a postulated pacemaker in the transverse colon. Retrograde peristalsis consists of annular contractions occurring most commonly in the right colon. These contractions work to keep the stool in the right colon and therefore facilitate absorption. As ileal effluent continues to empty into the cecum, some of the liquid stool flows to the transverse and descending colon, where segmentation predominates. This action consists of random, uncoordinated annular contractions over short segments that propel feces both proximally and distally. Finally, mass movement occurs as a strong coordinated contraction that starts proximally and propels colonic contents distally and occurs in concert with the gastrocolic reflex.
Bowel Habits
There is a broad range of normal bowel habits that varies across cultures. A cross-sectional study of 20,000 men and women across all age groups in Britain showed an average of 1-1.5 bowel movements per day, which increased with fiber and fluid intake and physical activity.
Defecation
The urge to defecate is stimulated by rectal stretch in response to feces. This elicits the rectoanal inhibitory reflex which causes relaxation of the internal anal sphincter and allows the rectal contents to be “sampled” by specialized mucosa in the anorectal transition zone. This mucosa contains sensory fibers that can discriminate between flatus and solid and liquid stool. Immediately following this sensory process, the external sphincter contracts and the contents are moved proximally back into the rectum. Flatus and stool can be discharged, if appropriate. If not, the rectum relaxes and the urge to defecate passes. Normal defecation requires regular colonic function, specifically with regards to stool consistency, in addition to coordinated colonic motility, rectal sensation, sphincter function, and pelvic floor relaxation. When the rectum senses presence of feces and the decision is made to defecate, intra-abdominal pressure is increased and the pelvic floor and anal sphincters relax, allowing the rectum to straighten. After elimination of the stool bolus, the sphincters and pelvic floor resume their tone.
Diarrhea
Diarrhea is defined by the loss of more than 300 mL of fluid per day and chronically affects 5% of the United States population. It can result in severe electrolyte disturbances and dehydration. There are four main etiologies of diarrhea—invasive, secretory, osmotic, and malabsorptive. Invasive diarrhea results when enterocytes are destroyed by pathogens such as Shigella, Campylobacter, and Entamoeba histolytica, resulting in low volume loose bowel movements with blood and leukocytes. Secretory diarrhea is the result of excessive secretion by colonocytes or enterocytes. This results in high volume, isotonic diarrhea with a low osmotic gap. The primary causes are enterotoxins produced by E coli and Vibrio cholera, and excessive serotonin secretion in the carcinoid syndrome. Osmotic diarrhea occurs when an osmotically active substance in the bowel lumen draws hypotonic fluid from the circulation. Osmotic diarrhea is characterized by high volume output with a high osmotic gap and no leukocytes. Most commonly, this occurs in patients with disaccharidase deficiencies such as lactose intolerance. Malabsorptive diarrhea results from the lack of normal digestive or absorptive processes. Pancreatic insufficiency results in loss of proteolytic and lipase activity causing steatorrhea. Whipple’s disease (caused by infection with Tropheryma whippelii) and celiac sprue (autoantibodies to gluten) are characterized by inflammatory changes with loss of absorptive capacity of the small bowel. Surgery can also cause malaborption. Extensive small bowel or colonic resections compromise the absorptive capacity and may result in diarrhea. A portion of patients undergoing cholecystectomy will also experience transient diarrhea with fatty meals due to the loss of the bile reservoir capacity of the gallbladder and subsequent steatorrhea.
CONSTIPATION
Epidemiology
Based on an epidemiologic review of the literature, constipation affects 7%-79% of the United States population with a mean of 16%. The wide variation in reports is likely due to broad definitions of constipation including infrequent or hard stools, excessive straining, or incomplete evacuation. Incidence is associated with lower socioeconomic and educational status, non-Caucasian ethnicity, female gender, and increasing age. Low fiber intake is especially important, as it normally bulks stool, triggering colonic motility.
Etiology
Although idiopathic constipation occurs, changes in bowel habits should prompt a search for a cause. Numerous medications cause constipation, such as opiates, antiemetics (ondansetron), antipsychotics (chlorpromazine, haloperidol, risperidone, clozapine), antihypertensives (calcium channel blockers, atenolol, furosemide, clonidine), as well as over the counter medications such as ibuprofen, calcium, and iron supplements. The patient should be asked about previous laxative use, as rebound constipation may occur in patients with a history of laxative abuse. Constipation can be a symptom of a systemic disease such as hypothyroidism, hyperparathyroidism, diabetes, electrolyte disturbance, or connective tissue disorders. It may result from a primary colonic disorder such as Hirschsprung, endometriosis, and benign or malignant strictures. Neurologic disease or injury, psychiatric illness, and physical or sexual abuse may be contributory.
If none of these factors is present, patients may be suffering from a functional constipation syndrome, such as colonic inertia, irritable bowel syndrome, or pelvic floor dysfunction. Patients with colonic inertia report lifelong constipation with laxative dependence. Irritable bowel syndrome (constipation subtype) causes irregular bowel habits, bloating, and abdominal pain classically relieved with bowel movements. Patients with pelvic floor dysfunction or obstructed defecation syndrome report incomplete evacuation and excessive straining that is often improved with digital manipulation. They may have coexistent urinary dysfunction, pelvic organ prolapse, and sexual dysfunction.
Diagnosis
Evaluation for constipation includes a history and physical examination, including review of medications, and digital rectal and anoscopic evaluation. Metabolic etiologies may be ruled out with laboratory tests including TSH, calcium, electrolytes, and blood sugar in the appropriate patient. Anatomic lesions can be identified by colonoscopy. This should be considered in any patient with alarm symptoms (hematochezia, anemia, or weight loss), refractory constipation, and patients who are due for age-appropriate colon cancer screening. Medical therapy with fiber supplementation and laxatives should be tried first. Patients should be encouraged to keep a written record of their bowel habits. In refractory cases, and those in which a functional disorder is suspected, additional testing is indicated.
Anorectal manometry and balloon expulsion test should be considered in severe, refractory cases of constipation where the etiology is not clear and in patients with symptoms of pelvic floor dysfunction. Manometry allows evaluation of the rectoanal inhibitory reflex, sphincter tone, rectal sensation, and coordination. Patients with constipation tend to exhibit a hypertonic internal sphincter with poor squeeze pressures. Electromyography may reveal nonrelaxation or paradoxical contraction of the puborectalis. Balloon expulsion can be performed as an adjunctive study. It involves placing a balloon in the rectum and filling it until the urge to defecate is perceived. The patient is then asked to evacuate the balloon. Normal function is indicated by the ability to evacuate a 50-100 mL balloon in less than 1 minute. This simple test was shown to have 88% sensitivity and 89% specificity for diagnosing defecatory disorders compared with defecography. Defecography (barium, scintigraphic, or magnetic resonance) is useful when the results of manometric testing are not diagnostic.
Colonic transit can be evaluated using radiopaque marker studies. Patients ingest 24 markers and avoid laxatives. An abdominal radiograph is taken on the fifth day with note made of the distribution and number of retained markers. Normal patients will have fewer than five retained markers. In fact, eighty percent of normal patients will have passed all markers by the fifth day. Colonic inertia, a primary disorder of colonic motility, is diagnosed when more than five markers are retained and are scattered throughout the colon. Obstructed defecation is suggested if markers have accumulated in the rectum. A more detailed examination involves ingestion of radiopaque markers daily for three consecutive days and taking abdominal films on the fourth and seventh days. The number and distribution of retained markers are compared with established normal controls.
Treatment
Initial treatment of constipation should focus on lifestyle and dietary modification. Physical activity, fluid intake, and consumption of fruits, vegetables, and whole grains are increased. A fiber supplement is started in an effort to soften and bulk the stool. A low dose is recommended at first and slowly increased to the desired effect to minimize bloating and flatulence.
Laxatives, stimulants, and enemas should be used only for short periods of time for treatment of acute discomfort. Osmotic laxatives include lactulose, magnesium hydroxide, sodium phosphate, and polyethylene glycol (MiraLAX). These work by increasing the intraluminal osmolarity, creating a gradient that reduces fluid reabsorption. Magnesium hydroxide should be avoided in patients with renal insufficiency. Polyethylene glycol is one of the most commonly recommended laxatives as it is safe and effective, even for use in the long term. Colonic irritants work by increasing motility. Examples include senna, cascara, and bisacodyl. These medications can be limited by crampy abdominal pain. Long-term use of senna and cascara causes melanosis coli (brown discoloration of the mucosa). Stool softeners such as mineral oil and docusate work by increasing stool fluid retention. Enemas stimulate bowel movements by causing direct rectal stretch and irrigation (saline, soap suds), or softening of the stool (mineral oil). Colonic irritants and enemas can cause reduced colon and rectal motility and should not be used for prolonged periods of time. Lubiprostone, linaclotide, and prucalopride are newer agents indicated for the treatment of refractory idiopathic constipation and constipation-predominant irritable bowel syndrome. They cause increased secretion via activation of chloride channels (lubiprostome and linaclotide) and 5-HT4 receptors (prucalopride).
Defecatory disorders, as diagnosed by anorectal manometry, are best managed using biofeedback and pelvic floor retraining. Patients can learn to relax and strengthen the pelvic floor muscles and can develop increased rectal sensation awareness. These techniques have been studied in a randomized fashion and have been shown to be superior to medical management.
Selected patients with constipation benefit from surgery if all functional aspects of defecation have already been addressed. If there is pelvic floor dysfunction, this should be first addressed using biofeedback. Surgery is considered if patients have obstructed defecation from mechanical reasons such as rectal prolapse, rectocele, enterocele, or sigmoidocele may benefit from procedures to address the specific condition. Patients with colonic inertia without pelvic floor dysfunction, irritable bowel syndrome, or diffuse upper gastrointestinal involvement are treated with abdominal colectomy with ileorectal anastomosis. Multiple other approaches, including segmental colectomy and preservation of the cecum have shown conflicting, but overall worse, outcomes. Complications have been reduced with the use of laparoscopic techniques, which have been shown to be safe and effective. The antegrade colonic enema procedure is used more often in pediatric patients. It involves bringing up a piece of bowel (appendix, ileum, cecum, and left colon have been described) to the abdominal wall to allow intermittent catheterization with irrigation of the colon. This technique has been reported in adults with obstructive defecation and neurologic deficits with success. Newer therapies such as sacral nerve stimulation are currently under investigation.
MICROBIOLOGY
The colon of the fetus is sterile but the process of colonization begins immediately after birth. There is marked variation in the composition of the microbial flora between individuals, likely related to genetic, environmental, and dietary factors. Humans have 10 times more bacterial cells in their bodies than human cells, and in fact, bacteria make up 50% of the dry weight of feces. Microbes are present throughout the gastrointestinal tract, and their concentration increases from proximal to distal, with the highest concentrations in the colon and rectum. The majority of colonic organisms are anaerobic, but there is a substantial population of facultative anaerobes. Bacteroides spp account for the 60%-70% of the bacterial flora. Other predominant organisms include Escherichia coli, Lactobacillus bifidus, Kelbsiella, Proteus, Clostridium, Enterobacter, and Enterococcus. Methanobrevibacter smithii is responsible for methane production.
These bacterial populations are instrumental for the health of the colon. They serve a barrier function and maintain epithelial integrity. Fermentation of undigested polysaccharides creates short chain fatty acids that are an important energy source for colonocytes. In addition, bacteria play an active role in the immune function of the gut. Healthy bacterial populations make it difficult for pathogens to establish infection. In addition, normal microbial flora also serves a role in numerous physiologic processes. They deconjugate unabsorbed bile acids, creating the pigments that give stool its characteristic color, synthesize vitamin K for systemic absorption and use, and recycle colonic nitrogen in the form of urea.
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DISEASES OF THE COLON AND RECTUM
LARGE BOWEL OBSTRUCTION
General Considerations
Fifteen percent of intestinal obstructions in adults occur in the large bowel and the incidence increases with age. Obstruction can result from actual pathology of the bowel wall including malignancy and strictures, mechanical problems such as volvulus, incarcerated hernia, and intussusception, or intraluminal factors such as fecal or foreign body impaction (Table 30–2). Benign strictures are commonly associated with diverticulitis or IBD, but may occur as a result of ischemia, radiation, or as a result of a surgical anastomosis. Acute functional obstruction of the colon (Ogilvie syndrome) can cause the same spectrum of clinical symptoms. It is important to differentiate pseudo-obstruction from mechanical obstruction because the management is different. In contrast to small bowel obstruction, adhesive disease of the large intestine is a very rare cause.
Table 30–2. Causes of colonic obstruction in adults.
A major factor in the clinical course of large bowel obstruction depends on the competence of the ileocecal valve. Ten to twenty percent of patients have an incompetent ileocecal valve which allows decompression of the large bowel contents into the ileum. However, in the majority of patients, the ileocecal valve does not allow reflux to occur, resulting in a closed loop obstruction with rapidly increasing intraluminal pressure (Figure 30–4). This results in impaired capillary circulation, mucosal ischemia, and subsequent bacterial translocation with systemic toxicity. This process ultimately progresses to gangrene and perforation. This same process occurs in volvulus, which by definition is a closed loop obstruction. The cecum has the largest diameter and therefore, by the law of LaPlace, is at greatest risk for perforation. The normal diameter is approximately 7 cm. The risk of perforation is high if the diameter increases acutely or to a size greater than 10-12 cm.
Figure 30–4. The role of the ileocecal valve in obstruction of the colon. The obstruction is in the upper sigmoid. A: The ileocecal valve is competent, creating a closed loop between the obstruction and the valve. Tension in the closed loop is increased further by emptying of gas and fluid from the ileum into the colon. B: The ileocecal valve is incompetent. Reflux into the ileum is permitted. The colon is relieved of some of its distention, and the small bowel has become distended.
Clinical Findings
The history and physical examination can help distinguish a large bowel obstruction from other causes of an acute abdomen and identify those patients requiring urgent therapy. Obstipation is a universal feature of complete obstruction, though the patient may pass stool and gas located distal to the obstruction after the initial symptoms begin. Classically, the digital rectal examination reveals an empty vault except in cases of distal fecal impaction. Vomiting is a late finding and may not occur at all if the ileocecal valve prevents reflux. If reflux decompresses the cecal contents into the small intestine, the patient may also present with symptoms of small bowel obstruction.
The onset of symptoms maybe acute or gradual, depending on the location and etiology of the obstruction. A patient may report a history of constipation for months preceding any acute obstructive symptoms. Deep, visceral, cramping pain from obstruction of the colon is usually referred to the hypogastrium. Right sided lesions tend to grow to a large size prior to causing obstruction owing to the larger diameter of the lumen and the liquid stool. Therefore, these lesions may be palpable on abdominal examination. If the patient reports repeated episodes of fever and abdominal pain, a diverticular stricture is suspected; a history of hematochezia and weight loss suggests colorectal cancer (CRC). Alternatively, when symptoms occur acutely, volvulus, incarcerated hernia, or intussusception are more likely. A patient with fever, leukocytosis, and peritonitis has likely progressed to develop intestinal ischemia and/or perforation.
Abdominal films will frequently reveal dilated colon outlining the abdominal cavity. The colon can be distinguished from the small intestine by its haustral markings, which do not cross the entire lumen of the distended colon. Sigmoid volvulus can be identified by a characteristic “coffee bean” appearance which represents a dilated loop of colon starting in the left-lower quadrant extending medially. This finding is seen in 60% of patients. Cecal volvulus tends to appear as a dilated loop originating in the right-lower quadrant extending medially. In patients with other forms of obstruction, the extent of distention is dependent on the competency of the ileocecal valve and its relation to the location of the obstruction. A transition point with no distal colonic gas indicates complete obstruction. If gas is present in the distal rectum, it can represent residual material present prior to the obstruction or the presence of a partial obstruction. In acute pseudo-obstruction, the colon is diffusely dilated with stool and gas throughout (Figure 30–5). A CT scan with rectal contrast is the most useful single test for large bowel obstruction because it can yield information regarding the location and etiology of the bowel obstruction. This has largely replaced contrast enema. A water-soluble contrast medium, such as gastrografin, should be used if strangulation or perforation is suspected. Barium should not be given orally in the presence of suspected colonic obstruction.
Figure 30–5. Plain radiograph demonstrating the dilated colon with pseudo-obstruction (Ogilvie syndrome). (Courtesy of Dr. Santhat Nivatvongs)
Treatment
An operation is almost always required for mechanical large bowel obstructions. The extent of surgery depends on the patient’s acuity and the etiology of the obstruction. The primary goals of treatment are resection of all necrotic bowels and decompression of the obstructed segment. Removal of the obstructing lesion is a secondary goal, but a single operation to accomplish both objectives is preferred whenever possible. Options include resection with primary anastomosis, resection with diversion, diversion alone, and endoscopic stent placement.
Endoscopic stents are being used as a bridge to surgery and as palliative therapy. When used in acutely ill patients with a malignancy, there is no clear advantage of endoscopic stent placement as a bridge to surgery in terms of mortality or complications. However, they do allow decompression of the obstruction and time for physiologic optimization. This can increase the chances of resection with primary anastomosis and reduce the chance for diversion. This comes, however, at the risk of stent-related perforation. Stents may be considered also for palliation in high risk patients whose obstructing cancers are not resectable; however, if the patient will tolerate it, a permanent diverting colostomy is a more durable option.
Generally speaking, obstructing lesions of the right colon can be resected in one stage if the patient’s condition is stable. If the patient’s condition is precarious or if the colon has perforated, the bowel should be resected and an ileostomy created. Intestinal continuity can be restored at a second operation. Intestinal bypass is sometimes used for unresectable lesions although the relief of the obstruction is not always as effective.
Obstructing lesions of the left colon more commonly require diversion. Ideally the lesion is resected at the initial operation. After resection, anastomosis may be postponed with creation of a temporary end colostomy and Hartmann’s pouch (Figure 30–6). If the patient’s clinical condition will allow it, a primary anastomosis may be performed with a diverting loop ileostomy if needed to protect the anastomosis. If resection is not possible, the bowel can be decompressed proximally and distally with a loop or double barrel colostomy. These stomas are difficult to manage and are associated with a high rate of prolapse and are thus, avoided if at all possible.
Figure 30–6. Primary resection for diverticulitis of the colon, also used in acute large bowel obstructions. The affected segment (shaded) has been divided at its distal end. If primary anastomosis is to be done, the proximal margin (dotted line) is transected, and the bowel is anastomosed end to end. If a two-stage procedure will be used, a colostomy is formed at the proximal margin, and the distal stump is oversewn (Hartmann procedure, as shown) or exteriorized as a mucous fistula. The second stage consists of colostomy takedown and anastomosis.
The prognosis depends upon the age and general condition of the patient, the extent of vascular impairment of the bowel, the presence or absence of perforation, the cause of obstruction, and the promptness of surgical management. The overall mortality rate is about 20%. Cecal perforation carries a 40% mortality rate. Obstructing cancer of the colon has a worse prognosis than nonobstructing cancer because it is more likely to be locally invasive or metastatic to nodes or distant sites.
Acute pseudo-obstruction of the colon (Ogilvie syndrome) presents with massive colonic distention in the absence of a mechanically obstructing lesion (Figure 30–5). It is a severe form of ileus that occurs most commonly in systemically ill patients and results from an imbalance in the autonomic tone with subsequent absence of peristalsis. Electrolyte disturbances and medications are contributing factors. These patients are usually recovering from major surgery or are hospitalized for other causes, most commonly cardiac disease, trauma, and infection. The mortality rate is 15% overall but increases to 30% in patients who develop ischemia or perforation.
The initial presentation may be missed in critically ill patients. Abdominal distention is the earliest manifestation, but later symptoms include abdominal pain, vomiting, and obstipation and may mimic those of true obstruction; however, 40% of patients will have diarrhea. The differential diagnosis includes toxic megacolon (in patients with ulcerative colitis [UC] and C difficile colitis) and mechanical large bowel obstruction. Plain x-rays of the abdomen show marked distention of the colon, often most severe in the right and transverse colon. Contrast enema proves the absence of obstruction, but instillation of radiopaque material should cease as soon as the dilated colon is reached. As opposed to a mechanical bowel obstruction, surgical management in Ogilvie syndrome is reserved for complications including perforation and ischemia.
If the patient has no signs of obstruction or perforation, the initial measures include nasogastric suction, rectal tube placement, fluid resuscitation, and correction of electrolyte imbalances. Systemic illnesses contribute and should be treated appropriately (respiratory failure, cardiac disease, and sepsis). All anticholinergic and narcotic medications should be discontinued. These measures will be effective in 75%-85% of patients. The patient should be followed with serial imaging. The risk of perforation is related to cecal diameter. The highest risk patients have a diameter > 10 cm and should be closely monitored. If there is any sign of clinical deterioration or no improvement in 48 hours, more aggressive treatment is warranted.
The acetylcholinesterase inhibitor neostigmine is an effective treatment for acute colonic pseudo-obstruction in patients without response to conservative measures. It works by acutely increasing acetylcholine levels in the body thereby prompting immediate bowel contraction and decompression. Patients require telemetry monitoring during and after administration as symptomatic bradycardia requiring atropine occurs in 10% of patients. The most common side effects include abdominal cramping and excessive salivation. It is successful in 90% of patients with a recurrence rate of 7%. If this is unsuccessful, or neostigamine is contraindicated (renal insufficiency, pregnancy, bronchospasm, bradycardia), colonoscopic decompression is the next step in management. Endoscopic decompression carries a risk of perforation but when performed by an experienced team, the risk of perforation is reduced to 2%. This procedure also offers the benefit of visualization of the colonic mucosa for evidence of ischemia. This is initially successful in 80% of patients, but recurrence is common. Ideally a tube is placed into the right colon using fluoroscopic guidance to maintain decompression.
In patients with refractory disease, surgical intervention is required. A percutaneous cecostomy tube is possible in patients who are high risk for surgery. If there is evidence of ischemia or perforation, patients are offered segmental or subtotal colectomy depending on the distribution of disease. This operation carries a high morbidity and mortality, likely related to patient’s underlying illness. Primary anastomosis is considered based on the patient’s clinical status, but often diversion is performed and intestinal continuity created at during a second procedure months after resolution of disease.
ASGE Standards of Practice Committee, Harrison ME, Anderson MA, et al: The role of endoscopy in the management of patients with known and suspected colonic obstruction and pseudoobstruction.Gastrointest Endosc 2010 Apr;71(4):669-679.
De Giorgio R, Knowles CH: Acute colonic pseudo-obstruction. Br J Surg 2009 Mar;96(3):229-239.
Godfrey EM, Addley HC, Shaw AS: The use of computed tomography in the detection and characterization of large bowel obstruction. N Z Med J 2009 Oct 30;122(1305):57-73.
Schwenter F, Morel P, Gervaz P: Management of obstructive and perforated colorectal cancer. Expert Rev Anticancer Ther 2010 Oct;10(10):1613-1619.
Tan CJ, Dasari BV, Gardiner K: Systematic review and meta-analysis of randomized clinical trials of self-expanding metallic stents as a bridge to surgery versus emergency surgery for malignant left-sided large bowel obstruction. Br J Surg 2012 Apr;99(4):469-476.
COLON CANCER AND POLYPS
Background
In the United States, colorectal cancer (CRC) ranks third after prostate and lung cancer in men, and after breast and lung cancer in women in both incidence and mortality. The American Cancer Society predicts that in 2012, more than 143,000 patients will be diagnosed and 51,000 will die as a result of their disease. Men have a higher incidence and mortality than women, and Black Americans have a higher incidence and mortality than other ethnic groups. The overall incidence and mortality from CRC has been decreasing since the early 1980s, likely owing to improved screening. The frequency of CRCs by location in the colon is shown in Figure 30–7. The average age at diagnosis is 68 years for men and 72 years for women.
Figure 30–7. Distribution of cancer of the colon and rectum.
The average lifetime incidence of CRC in the United States is more than 5%. Multiple risk factors for CRC have been identified. The most significant are considered non-modifiable. For instance, having a single first degree family member with a diagnosis of CRC increases one’s lifetime risk by 2.2. If the relative is diagnosed at an early age, the risk is increased by 3.9 and if there is more than one relative, this risk increases to 4.0. The most significant personal risk factors include IBD, especially with pancolitis, a history of adenomatous polyps, diabetes, and obesity. Modifiable risk factors include increased red and processed meat consumption, smoking, and alcohol. Case control and cohort studies have suggested that protective factors include a high fiber diet, calcium as well as vitamin D supplementation and physical activity. Randomized controlled intervention trials have been unable to demonstrate that these interventions significantly reduce risk for CRCs; however, they are limited by the older age of the study population at the time of intervention, poor adherence, and a relatively short follow up. A large Danish cohort study concluded that 25% of cancers are preventable through a healthy lifestyle.
In addition to lifestyle, chemoprevention in colon cancer has also been suggested as a way to reduce the burden of disease. Celecoxib and low dose aspirin have been shown to reduce the rate of metachronous adenomas in average risk patients found to have adenomas on screening colonoscopy. However, the adverse effects of these medications including cardiovascular events with celecoxib and peptic ulcer disease with aspirin likely outweigh these risks and therefore their use is limited in average risk patients. However, the benefits of celecoxib are more likely to outweigh the risk in patients with familial adenomatous polyposis (FAP), an inherited CRC syndrome, and it has been FDA approved for this indication.
Genetics
CRC develops through a stepwise accumulation of mutations that allow the progression of normal mucosa to adenoma to carcinoma in a pathway known as Loss of Heterozygosity. The inciting event in 85% of sporadic CRCs is the development of chromosomal instability. This allows a cell to accumulate inactivating mutations in tumor suppressors such as adenomatous polyposis coli (APC), P53, deleted in colorectal carcinoma (DCC) and SMAD 4, as well as activating mutations in oncogenes such as K-ras, c-myc, c-src, and BRAF in a stepwise fashion. A less common pathway involves the development of mutations in the genes responsible for DNA mismatch repair and subsequent microsattelite instability. A third mechanism involves the epigenetic silencing of tumor suppressor genes though abnormal methylation. The familial cancer syndromes are caused by germline mutations in these genes, such as APC in familial adenomatous polyposis and mismatch repair genes in Lynch Syndrome, also known as hereditary nonpolyposis colorectal cancer (HNPCC). Approximately 5% of CRCs occur in patients with a hereditary syndrome.
HEREDITARY NONPOLYPOSIS COLORECTAL CANCER
The most common genetic colon cancer syndrome is Lynch syndrome, formerly known as HNPCC. The name of the condition has reverted to Lynch syndrome as these patients may have polyps in addition to cancer. It is an autosomal dominant condition with 80% penetrance whose basis is a mutation in the DNA mismatch repair system clustered on chromosome 2p. Ninety percent of all patients have a mutation in MLH1 or MSH2 which results in microsatellite instability (MSI). Other known mutations include MSH6, PMS2, and PMS1. The lifetime risk of CRC is 66% in men and 43% in women with a median age at diagnosis of 42 and 47 years, but this varies between affected families depending on the mutation. These cancers tend to occur in the ascending colon. A hallmark of the disease is the association with other cancers, including the endometrial, ovarian, gastric, upper urinary tract, biliary, small bowel, and brain.
The diagnosis is usually suspected on clinical grounds using the patient’s medical and family history. Four sets of criteria were developed to help make the diagnosis. The Amsterdam criteria were initially developed in 1990 and are based on an accurate, extended family history of colon cancer. They were found to have a sensitivity of 61% and a specificity of 67% for the diagnosis. In 1999 the Amsterdam II criteria were published, which increased the sensitivity by including extracolonic cancers (Table 30–3a). Patients who meet either of these criteria should be offered genetic testing, which can be used to provide diagnostic and prognostic information for the patient and his or her family. A separate set of criteria, known as the Bethesda Guidelines, was published in 1997 (Table 30–3b). These were designed to have very high sensitivity (94%) at the expense of specificity (49%) and are used to select tumor specimens appropriate for MSI testing. If this test is positive, it is followed by a confirmatory genetic test for the HNPCC mutations, because 15% of sporadic CRC exhibit MSI.
Table 30–3a. Amsterdam I and II criteria.
Table 30–3b. Revised Bethesda criteria.
Once a diagnosis has been made, an aggressive screening regimen is initiated including colonoscopy every 1-2 years starting at age 20-25. Women are advised to undergo endometrial cancer screening or hysterectomy if childbearing is complete. In families with a history of upper urinary tract or gastric cancers, screening for renal and ureteral cancer is initiated at age 30-35 years. A decision analysis model suggested that prophylactic total abdominal colectomy at age 25 would offer a very small survival benefit (1.8 years) and a decreased quality of life compared with colonoscopic surveillance. Therefore, surgical intervention is generally reserved for patients who develop a cancer or polyp that is unable to be removed endoscopically. However, because metachronous tumors occur in 40% of patients at 10 years an aggressive surgical approach is warranted. If a patient presents with a colon cancer, one option would be total abdominal colectomy with ileorectal anastomosis; however, even with this aggressive approach, the risk of developing a future rectal cancer is 6%-20%. Because any rectal remnant left in situ is a risk for developing a future cancer, an aggressive approach is appropriate; however, the decision regarding the specific intervention is multifactorial and depends on the patient’s preoperative continence, ability to cope with the change in bowel habits that occur after low anastomoses, and desire to participate in postoperative surveillance. If the patient prefers protectomy or presents with a rectal cancer a restorative proctocolectomy with ileal pouch anal anastomosis (IPAA) (J-pouch) can be offered if safe from an oncologic perspective. However, if the tumor precludes sphincter preservation or the patient is otherwise not a candidate for a J-pouch, a total proctocolectomy with end ileostomy is performed.
FAMILIAL ADENOMATOUS POLYPOSIS AND MYH-ASSOCIATED POLYPOSIS
The second most common CRC syndrome is FAP. This syndrome accounts for less than 1% of all CRCs. Like HNPCC, it is autosomal dominant with nearly 100% penetrance; however, in contrast, these patients are more likely to develop left-sided CRC at an earlier age (> 90% by age 40). Twenty percent of cases of FAP are sporadic. Most are a result of a mutation of the DNA mismatch repair gene APC located on chromosome 5q21. Depending on the location and type of mutation, the phenotypic presentation can range from mild to severe. Individuals with classic FAP typically have more than 100 colonic adenomas but can have more than 1000. These develop at an early age and are present in 50% of patients by age 15. In contrast, patients with attenuated FAP (aFAP) have an average of 30 polyps that develop after age 25. Although most patients with the attenuated form develop colon cancer, the average age is 59 years.
MYH-Associated polyposis (MAP) is clinically similar to FAP and aFAP. Most patients develop a mean of 50 polyps, although cases have been documented with 5-750. However, it is distinguished by family history as it is an autosomal recessive condition caused by mutations in the base excision repair gene MYH.
There are a variety of extracolonic manifestations described in patients affected by the polyposis syndromes. Duodenal neoplasms and desmoid tumors occur in 85% and 15% of patients, respectively. These two manifestations are important because they contribute to increased morbidity and mortality in FAP patients. Esophagogastroduodenoscopy (EGD) is recommended for duodenal screening in these patients beginning at the age of 20. Desmoid tumors are commonly intra-abdominal in FAP patients. They are often found incidentally at surgery but can be aggressive and result in significant GI symptoms. Other manifestations include retinal pigment epithelium hypertrophy, osteomas, and sebaceous cysts. Gardner syndrome is applied to families with the constellation of polyposis, osteoma, dental abnormalities, and soft tissue tumors; Turcot syndrome refers to patients affected by polyposis and medulloblastoma.
Management involves genetic counseling, aggressive screening, and prophylactic colectomy. Patients at risk for FAP should undergo initial colonoscopy at the age of 12, or 20 if suspected to have aFAP. Considering the predominantly left-sided disease in FAP, it has been suggested that these patients can be followed with annual or biannual flexible sigmoidoscopy; however patients with aFAP should be followed with colonoscopy. Prophylactic colectomy is warranted in all patients, especially those with severe polyposis, dysplasia, symptoms, or large adenomas. This can be delayed if there is a mild presentation, but otherwise should be performed as soon as practical. Options are the same as those for HNPCC, and include total proctocolectomy with end ileostomy, restorative proctocolectomy with IPAA, and total abdominal colectomy with ileorectal anastomosis, again depending on preoperative bowel function and patient preference. Abdominal colectomy is reserved for patients with rectal sparing and attenuated disease, which most often occurs in the presence of a specific mutation upstream of c1250. However, the retained rectum is still at risk and these patients still require surveillance proctoscopy with resection or destruction of polyps every 6 months. More commonly, patients elect to undergo restorative proctocolectomy with IPAA. Patients who have a stapled anastomosis will retain about 1 cm of the anal transition zone (ATZ) and due to the predilection for ileal polyps, patients undergoing IPAA require lifelong surveillance. Some surgeons favor mucosectomy to reduce the risk of polyps in the ATZ but the ileal polyps are not affected and the functional outcome of a mucosectomy with handsewn anastomosis is less favorable than for those with a stapled anastomosis. Celecoxib is approved by the FDA for chemoprevention and may be a useful adjunct in these patients. Even with perfect surveillance and appropriate surgical management, FAP patients have an excess mortality related to extracolonic disease including upper GI malignancy and desmoids.
JUVENILE POLYPOSIS
Juvenile polyposis is a rare syndrome characterized by the development of excessive non-adenomatous polyps. It is an autosomal dominant condition, most commonly associated with germline mutations in the SMAD4 or BMPR1A genes. The polyps are a distinct histologic subtype referred to as “juvenile” polyps, which are similar to hamartomas with edematous lamina propria and inflammatory changes. Although the pathway to carcinoma in these patients has not yet been fully elucidated, these patients have an elevated lifetime risk of developing CRC of 39%-68%. It is thought that carcinoma development is a result of neoplastic epithelial changes in the setting of exposure to the inflammatory stromal environment. The syndrome is diagnosed by the presence of five or more juvenile polyps in the gastrointestinal tract or the presence of any number of juvenile polyps with a family history of juvenile polyposis. There are three associated syndromes: Cronkhite–Canada syndrome (juvenile polyposis and ectodermal lesions), Bannayan–Riley–Ruvalcaba syndrome (juvenile polyposis, macrocephaly and genital hyperpigmentation), and Cowden disease (juvenile polyposis, facial trichilemmomas, thyroid cancer, goiter, and breast cancer).
These patients should undergo surveillance of the entire gastrointestinal tract for polyps beginning at the time of diagnosis or the onset of symptoms. This should continue annually in the presence of polyps. However, if the patient is polyp-free, the interval can be extended to 2-3 years. Surgery is reserved for patients with severe diarrhea, bleeding, or intussusception, those who fail endoscopic management of their polyps, exhibit dysplastic changes, and for those patients with a strong family history of CRC.
PEUTZ–JEGHERS SYNDROME
Peutz–Jeghers syndrome is a rare autosomal dominant condition (1/200,000 population) caused by a mutation in the STK11 gene on chromosome 19. The syndrome is defined by multiple hamartomas in the gastrointestinal tract (stomach to the rectum), mucocutaneous pigmentation, and elevated risk of gastrointestinal, breast, pancreatic, cervical, ovarian, and testicular cancers. The lifetime risk of CRC is reported to be 39%. Diagnosis is made in patients with two or more Peutz–Jeghers polyps or a combination of polyps, mucocutaneous pigmentation, or family history. There is insufficient evidence to suggest that the polyps themselves represent a premalignant lesion; however, they do become symptomatic in 50% of patients by the age of 20. Symptoms include anemia secondary to bleeding and abdominal pain secondary to infarction, intussusception, or obstruction. Because of the rarity of the condition, management has not been well defined. Regular endoscopic surveillance (including small bowel capsule endoscopy) is advocated for the early detection of malignancy and resection of symptomatic lesions. This is recommended to begin at age 8, with the frequency determined by the burden of hamartomas. When endoscopic removal is not possible, exploratory surgery with resection and intraoperative small bowel endoscopy is advised. These patients also must undergo appropriate screening for the extra-intestinal malignancies. Optimal regimens are under active study.
COLORECTAL CANCER SCREENING
CRC screening is important for two reasons. The first is the early detection of colorectal carcinomas and the second is preventing CRC through the identification and removal of colorectal adenomas, which are cancer precursors. Trials have shown that the detection of early CRCs by surveillance reduces mortality. Similarly, patients who undergo endoscopic removal of adenomas have a 53% reduction in CRC-specific mortality at 16 years. The benefit is increased in patients with above average risk for CRC.
The most updated guidelines on CRC screening were published in 2008. This includes three separate guidelines from the American College of Gastroenterology (ACG), the United States Preventative Services Task Force (USPSTF), and a joint guideline from the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer (which includes the American Society of Colon and Rectal Surgeons), and the American College of Radiology (Table 30–4). While they vary in certain recommendations, all agree that screening for average risk patients should begin at age 50 and should occur at regular intervals depending on the method, of which several are available. These include fecal occult blood test (FOBT), fecal immunochemical test (FIT), stool DNA, barium enema, CT colonography, flexible sigmoidoscopy, and colonoscopy. All abnormalities detected by screening tests require a colonoscopy for diagnosis and treatment. The decision of which method to use must be individualized, taking into account several factors, including sensitivity and specificity, risks, costs, patient adherence, and availability. The ACG guidelines suggest that African American men should begin screening at age 45. The USPSTF guidelines recommend screening selectively in patients between ages 75 and 85 years and not screening patients over 85 years. The USPSTF does not recommend the newer stool DNA and CT colonography tests until more performance data are available. All guidelines agree that prevention of colon cancer is the primary goal of screening and that the decision should be made on an individual basis to maximize effectiveness.
Table 30-4. American Society of Colon and Rectal Surgeons guidelines for colorectal cancer screening.1
All methods have their strengths and weaknesses. Stool tests, like FIT, FOBT, and the stool DNA test are noninvasive with essentially no risks. They are more acceptable to patients as a screening modality; however, there is poor adherence in clinical trials on the part of both the physician and patient with the examination not being performed at the proper intervals or patients not undergoing colonoscopy for positive tests. The sensitivity of FOBT is poor (33%-40%), but this increased to 50%-75% with the development of the SENSA FOBT that is now the standard. Sensitivity and the false positive rate were addressed with the development of the stool DNA test and FIT, although these are substantially more expensive and, as mentioned, the stool DNA test is still undergoing clinical trials. It is important to note that these tests are not designed for prevention, but rather for early detection, as most advanced adenomas are not detected by these tests.
Radiographic options, including barium enema and CT colonography, are more sensitive for the detection of malignant and premalignant lesions. Both require full bowel preparation and have the drawback of radiation exposure; however, procedural risk is low. Barium enema has fallen out of favor as a screening test as it cannot detect small lesions, is unable to provide pathologic information and is very uncomfortable for patients. As CT colonography is still early in its development, its performance and appropriate screening intervals has yet to be defined; however it has been shown to have good sensitivity and specificity. It has a 90% sensitivity and a specificity of 86% for polyps more than 1 cm in size. For polyps more than 6 mm, sensitivity was 78% and specificity 88%. It is likely a poor test for detecting sessile adenomas. Using a cutoff of 6 mm for referral for colonoscopy, 15%-25% of patients would be referred, requiring an additional bowel preparation and the cost of another procedure. In addition, 5%-16% of patients will have an incidental extracolonic finding requiring further evaluation.
Flexible sigmoidoscopy is not often used in the United States for screening purposes. Its utility in preventing CRC is limited because it does not evaluate the proximal colon. It is therefore combined with a fecal screening test and colonoscopy is recommended if the fecal test is positive. Colonoscopic studies have shown that 30% of patients with advanced adenomas have no distal lesions and would therefore have a normal examination to the splenic flexure. This is more common in women and patients over age 60. This, in combination with the need for bowel preparation, patient discomfort, and poor reimbursement, has made this test infrequently utilized for screening purposes.
Colonoscopy at 10-year intervals is the preferred screening test in the ACG guidelines and is the final common step in every screening program for CRC. Its major drawback is poor adherence, likely related to the need for bowel preparation and sedation, which usually requires a chaperone and a day off work. It is the most expensive screening test and does have a small but real risk of complications (3-5/1000). A concern for missed lesions has prompted the development of tools for measuring quality. However, it is overall a safe and effective screening regimen.
Screening for high risk patients is individualized. Children with possible FAP should begin screening at puberty. Patients in families with HNPCC should begin at age 21. Patients with UC for more than 10 years should begin annual colonoscopy with random biopsies. Patients with a history of early (< age 60) CRC in one first degree relative are offered colonoscopy starting at age 40, or 10 years earlier than the family member’s diagnosis. The most recent ACG recommendations state that patients with a family history of CRC occurring in one family member older than age 60 may undergo screening as an average risk patient.
SPORADIC COLORECTAL POLYPS
The term “polyp” is a morphologic term given to tissue that project into the lumen of the gastrointestinal tract and therefore is a broad term encompassing many entities, both benign and malignant. Non-neoplastic polyps account for 90% of all colonic polyps. Subtypes include juvenile, hyperplastic, and inflammatory polyps, as well as hamartomas (Table 30–5). There have been rare reports of carcinoma developing in association with hamartomas, but in general these polyps do not portend an increased risk for cancer. Neoplastic polyps, or adenomas, are the precursor lesions to the vast majority of colorectal adenocarcinomas in a well-studied “polyp to carcinoma” sequence, where colonic mucosa transforms into small tubular adenomas, increases in size, and develops high risk features prior to frank carcinoma. The genetic mechanisms behind this process have been well characterized and are discussed above. An exception to this is the more recently recognized serrated adenoma, which can be difficult to distinguish from hyperplastic polyps. These are found more commonly in the right colon and are thought to progress to carcinoma via MSI.
Table 30-5. Polyps of the large intestine.
Adenomas, while accounting for only 10% of polyps, are common. Screening colonoscopy in asymptomatic patients detects adenomas in 25% of men and 15% of women. In autopsy series, they are detected in up to 60%. They are more common in older age with a prevalence of 30% at age 50 years and 55% at age 80. About 50% of patients with adenomas have more than one lesion, and 15% have more than two. They are predominantly found distal to the transverse colon and approximately half occur in the rectosigmoid area of the colon.
The presence of an adenoma indicates an increased risk for CRC. Further, adenomas themselves may harbor malignancy. The characteristics of the adenoma, including histology, location, shape, and size, significantly influence this risk. Adenomas are subdivided into tubular, tubulovillous, and villous subtypes and these exist on a spectrum. If followed over time, only 5% of tubular adenomas will develop into a malignancy, however, 22% of tubulovillous and 40% of villous adenomas will progress. Further, risk increases with size. Adenomas less than 1 cm harbor carcinoma only 1% of the time, however this risk increases to 10% in adenomas 1-2 cm and 45% of adenomas greater than 2 cm. Other factors include sessile (as opposed to pedunculated) polyps, location in the ascending colon, male sex, age greater than 60, and family history. Overall, the greatest risk factors for both the presence of carcinoma within a polyp and the future development of CRC are size greater than 1 cm and tubulovillous or villous histology. These have been termed “advanced adenomas.” Of note, these polyps require surgical resection more often as these features make them less amenable to endoscopic methods.
Adenomas, even in the absence of malignancy, are associated with risk of CRC. Patients found to have adenomas have a risk of developing metachronous cancers twofold to fivefold over patients without them. The risk is estimated to be 5%-10% per year. For these reasons, the consensus guidelines recommend complete excision of the adenoma plus more frequent colonoscopic surveillance. Colonoscopy is repeated at 5-10 years for 1-2 low risk adenomas, at 3 years if 3-10 low-risk or any high-risk adenomas, and less than 3 years if greater than 10 adenomas. Colonoscopy is repeated sooner if there is a question regarding the adequacy of the polypectomy.
Although techniques for endoscopic polypectomy are improving, surgery still remains an important option in the management of colorectal polyps. Surgery is indicated if complete endoscopic resection is not possible. Large polyps, sessile polyps, and those found in the distal rectum are the most challenging to manage endoscopically and result in a higher likelihood of positive margins or incomplete removal. Because up to 20% of these will harbor carcinoma, they require surgical resection. Surgery is also indicated in some completely resected polyps found to contain invasive adenocarcinoma.
Carcinoma is found in 5% of benign appearing endoscopically resected polyps. In 1985, Haggitt reported that depth of invasion was the most important indicator of metastasis and developed a classification system based on depth of invasion (Table 30–6). Level 1, through 4 (limited to proximal two-thirds of submucosa) with favorable histology have a < 1% risk of nodal metastasis and are adequately treated by endoscopic resection with a margin > 2 mm. However, carcinomas exhibiting evidence of vascular or lymphatic invasion, indeterminant margins, a margin < 2 mm, or level 4 with invasion into distal third of submucosa have a 12%-25% chance of lymph node involvement and therefore require formal oncologic resection.
Table 30-6. Haggitt classification.1
Clinical Findings
The majority of patients with CRC are asymptomatic. Based on a median doubling time of 130 days, it takes at least 5 years, and often 10-15 years, before a cancer causes symptoms. When symptoms do appear, they are variable, non-specific, and often indicate an advanced lesion or complications. CRCs may cause subclinical bleeding, resulting in an asymptomatic iron deficiency anemia. For this reason, any iron deficiency anemia in a male or nonmenstruating female should prompt a work up to rule out bleeding from the GI tract. However, one-third of patients with CRC have normal hemoglobin at the time of diagnosis. A minority of patients will present emergently with acute obstruction, perforation, or significant bleeding with symptomatic anemia.
Compared with the left colon, tumors of the right colon may reach a more advanced stage before they cause symptoms. Obstruction is rare because the right colon is larger in diameter and has liquid stool. If these tumors bleed, melena, or more commonly occult blood, will be present in the stool. There may be associated vague abdominal pain. Ten percent of patients present with a palpable abdominal mass.
In contrast, the left colon and rectum has a smaller diameter and semisolid feces. Tumors here can cause luminal narrowing and obstruction resulting in narrowing of the stool, constipation, and increased frequency of bowel movements. Rectal cancer can produce tenesmus. When bleeding occurs, it tends to be dark to bright red and may streak or be mixed with the stool. Any patient with ongoing hematochezia, even in the presence of another clinical explanation, such as hemorrhoids, must undergo evaluation for CRC.
Physical examination may help localize and determine the extent of disease. The abdomen should be palpated for masses and the liver examined to rule out enlargement. Auscultation of the lungs is poorly sensitive for metastatic disease. A digital rectal examination may detect a distal rectal cancer. Its location, size, and mobility should be noted. Retrorectal nodes or drop metastases in the Pouch of Douglas (Blumer shelf) may be palpated. Rigid proctoscopic examination gives an accurate location of the tumor, which is important for treatment planning. Lymph node examination may reveal metastasis in the supraclavicular nodes.
The preoperative work up for CRC will determine a clinical stage, allow initial prognostics, and inform the treatment plan. It consists of laboratory tests, radiographic imaging, and endoscopy with biopsies.
Useful laboratory tests include a complete blood count, serum chemistries, urine analysis, and liver function tests as clinically indicated. These will detect anemia and other abnormalities that may need to be addressed prior to initiating treatment. The serum marker for CRC is carcinoembryonic antigen (CEA). It is a glycoprotein found throughout the gastrointestinal tract as well as other tissues. It is not sensitive or specific for patients with CRC, specifically for patients without metastatic disease. It is therefore not recommended as a screening test; however, it has been shown to be a useful adjunct to postoperative monitoring for recurrence, specifically in patients with an elevated preoperative CEA that returns to normal after surgery.
Colonoscopy is the gold standard for the diagnosis of CRC. Complete colonoscopy is indicated in all patients who have suspected or known CRC. It allows tissue diagnosis, localization of the lesion using tattoo, and evaluation for synchronous neoplasms. Three percent of patients with a known colon or rectal cancer have a synchronous lesion. In patients with obstructing lesions, the remaining colon should be evaluated using contrast enema or CT scan. These patients should undergo postoperative surveillance as soon as feasible after their surgery.
CRC generally grows circumferentially. It takes approximately 1 year for a tumor to encircle three-fourth of the circumference of the bowel wall. This is especially true in the left colon which is smaller in diameter. Submucosal extension through the lymphatic network rarely extends beyond 2 cm from the tumor. As the tumor extends radially, it may penetrate the wall and extend into neighboring structures including the liver, greater curvature of the stomach, duodenum, small bowel, pancreas, spleen, bladder, kidney, ureter, and abdominal wall. Rectal tumors in particular may invade the vaginal wall, bladder, prostate, sacrum, or levators due to the confined space of the pelvis. The inflammatory response incited by extension of the tumor is indistinguishable from frank invasion during gross examination at the time of surgery.
Metastatic disease most often occurs through the lymphatics, although it is also known to occur via seeding, intraluminal spread, or hematogenously. Rectal cancer metastasizes proximally to the mesorectal, iliac, and inferior mesenteric lymph nodes, as well as radially along the pelvic side walls where obturator nodes can become involved. Very distal rectal cancers can also spread to inguinal lymph nodes. Colon cancer spreads along the superior and inferior mesenteric lymph node basins (Figure 30–8). Approximately half of patients undergoing surgery for CRC will have lymph node involvement. Hepatic and pulmonary metastases occur via hematogenous invasion. In colon cancer this may occur through the portal system to the liver, and less commonly the lumbar and vertebral veins to the lungs and other organs. Metastases to ovaries are mostly hematogenous; they are found in 1%-10.3% of women with CRC. Rectal cancer spreads through the systemic circulation via the hypogastric veins.
Figure 30–8. Lymphatic drainage of the colon. The lymph nodes (black) are distributed along the blood vessels to the bowel.
The “no touch” technique, while never definitively shown to reduce metastatic disease or improve survival, is one of the basic tenets of surgical management of colon cancer. The concept is to minimize manipulation of the tumor prior to ligation of the blood supply in order to avoid tumor embolus and subsequent metastasis. Transperitoneal metastasis or peritoneal “seeding” may occur when a tumor has extended through the serosa leading to peritoneal implants or generalized carcinomatosis. When found in the Pouch of Douglas, these deposits are palpated on digital rectal examination and referred to as Blumer’s shelf.
Accurately staging patients with CRC is important as it allows the development of an adequate treatment plan and determination of prognosis. The clinical stage is determined using preoperative imaging. Pathologic staging is based on imaging and information obtained after resection.
The initial determination required for developing a treatment plan for a patient with colon cancer is whether the tumor is resectable. This can be determined by searching for metastatic disease and determining local invasion. CT of the abdomen and pelvis is used routinely for this purpose. It may reveal lymphadenopathy, hepatic metastases, as well as evidence of obstruction, perforation, or direct extension (Figure 30–9). It has a sensitivity of about 78% for metastatic disease. Metastatic disease to the lungs is most often assessed using a routine preoperative chest x-ray. CT can be used to further evaluate abnormalities; however, it is not used as an initial test because these patients generally do not develop pulmonary metastases without first developing liver disease. This is because the lymphatic drainage of the colon follows the portal circulation. Positron emission scanning (PET) is not routinely recommended, however it is indicated in patients with suspicious abnormalities on CT that require evaluation for proper treatment planning.
Figure 30–9. CT scan images. A: Primary, circumferential carcinoma of the sigmoid colon (arrow). B: Hepatic metastasis (arrow).
Surgical planning for rectal cancer requires detailed evaluation of the depth of invasion of the rectal wall as well as lymph node involvement and invasion of nearby pelvic structures including the levators, sphincter complex, and genitourinary tract. This information is used to make decisions about neoadjuvant therapy, sphincter sparing procedures, and local excision (LE). Endorectal ultrasound (ERUS) and pelvic magnetic resonance imaging (MRI) are commonly used. ERUS is particularly useful for determining the depth of invasion of the rectal wall and lymph node involvement. MRI is used to detect involvement of the mesorectal fascia and nearby pelvic structures to determine the likelihood of a circumferential resection margin, which is an important predictor of local recurrence. CT and PET CT are often used to assess pulmonary and liver metastasis, although the utility of this imaging modality requires further study.
The standard staging system in the United States is the tumor, node, metastasis (TNM) staging system from the American Joint Committee on Cancer (AJCC). This has replaced the Dukes classification. These are shown in Table 30–7. The clinicopathologic stage is the most important determinant of survival. Stage for stage, patients with colon cancer have a better prognosis than patients with rectal cancer. Similarly, patients with proximal rectal cancers have a better prognosis than those with distal cancers. Poor prognostic factors include complications such as obstruction or perforation, as well as histologic features such as poor differentiation and lymphovascular or perineural invasion.
Table 30-7. TNM classification of cancer of the colon and rectum.1
TREATMENT OF COLON CANCER
Surgery
Surgical resection of colon tumors is generally performed for patients with curative intent. Patients who are stage I-III or stage IV with resectable metastatic disease in the liver and/or lung are candidates for surgery. However, operative intervention may be necessary in patients with metastatic disease not amenable to complete surgical excision to treat complications of the primary tumor such as obstruction, perforation, or bleeding. Options include resection, diversion, and endoscopic stent placement. Emergency surgery has been associated with significant morbidity (30%) and mortality (10%). For patients specifically with obstruction, a meta-analysis showed no clear advantage of endoscopic stent placement as a bridge to surgery in terms of mortality or complications. In patients with unresectable disease, there is no evidence that prophylactic resection of the primary tumor improves prognosis or outcomes compared with primary chemotherapy treatment. These patients may become resectable after treatment with chemotherapy.
When possible, a laparoscopic approach to colon resection is preferred in most patients as it is associated with decreased hospital stay, postoperative pain, duration of ileus, and better pulmonary function and postoperative quality of life. The long-term oncologic outcomes for the open and laparoscopic approaches have been examined with multiple randomized controlled trials and are equivalent. This approach is not always appropriate for patients with obstructive or perforated lesions and should be abandoned in patients with prohibitive adhesions.
Upon entering the abdomen, the first step is to explore the abdominal cavity to search for metastatic disease not identified on preoperative imaging. If there are no findings that would preclude colectomy, attention is turned to resection. A “no touch” technique minimizes manipulation of the tumor prior to ligation of its blood supply to reduce tumor embolization which has a theoretical risk of causing metastatic disease. Although the extent of resection depends on the necessary lymphadenectomy, a margin of 5 cm on each side of the lesion in the bowel wall is generally considered adequate for clearance of any intramural spread. If there is any invasion into adjacent structures, these must be excised en bloc to achieve negative margins.
An important aspect of the surgical management of colon cancer is the removal of the draining lymph node basin because this allows accurate staging and treatment. Lymph node status is the most sensitive predictor of survival and adjuvant chemotherapy prolongs survival. Sentinel lymph node mapping has been trialed but with poor sensitivity and specificity with both technetium colloid and lymphazurin blue. Therefore, resection of all draining mesenteric lymph nodes remains the standard of care, often necessitating a larger segmental resection than would otherwise be needed for the purpose of margins. An adequate lymphadenectomy contains 12 or more lymph nodes. The extent of resection of the colon and mesocolon for tumors in various locations is shown in Figure 30–10.
Figure 30–10. Extent of surgical resection for cancer of the colon at various sites. The cancer is represented by a black disk. Anastomosis of the bowel remaining after resection is shown in the small insets. The extent of resection is determined by the distribution of the regional lymph nodes along the blood supply. The lymph nodes may contain metastatic cancer.
A right hemicolectomy is performed for tumors of the cecum and ascending colon. This requires high ligation of the ileocolic, right colic, and right branches of the middle colic artery. If the tumor is at the hepatic flexure or proximal transverse colon, an extended right hemicolectomy is performed with additional ligation of the middle colic artery. During mobilization of the ascending colon and hepatic flexure the surgeon must identify and protect the right ureter, superior mesenteric vessels, and duodenum.
A transverse colectomy with ligation of the middle colic artery is indicated for tumors in the transverse colon. If the tumor is in the splenic flexure or descending colon, a left hemicolectomy is performed with ligation of the IMA at its origin and resection of the distal transverse, descending, and proximal sigmoid colon. Sigmoid tumors are treated with sigmoid colectomy which includes part of the descending colon and proximal rectum. Tumors of the rectosigmoid and upper third of the rectum are removed with an anterior resection, requiring ligation of the sigmoid arteries as well as the middle hemorrhoidal arteries. The extraperitoneal rectum is mobilized and if needed, the splenic flexure may also be mobilized to ensure a tension free anastomosis. With all these resections, attention must be paid to the identification and preservation of the ureters, right kidney, and spleen. Stapled ileocolic anastomoses are associated with a decreased leak rate compared with hand-sewn. However, there does not appear to be a superior type of anastomosis in colocolonic or colorectal anastomoses. Thus, after resection for non-right sided colon cancers, the type of anastomosis is best left to the discretion of the surgeon.
Chemotherapy
Adjuvant chemotherapy is standard of care for patients with stage III (node positive) disease and has been shown to improve survival by 33% and reduce recurrence by 40%. Chemotherapy regimens are based on 5-fluorouracil (5-FU) with levisimole and oxaliplatin (FOLFOX) or capecitabine. Determination of KRAS mutations may also dictate therapy as research shows that two drugs used for CRC, cetuximab (Erbitux) and panitumumab (Vectibix), are not effective in tumors that carry the KRAS mutation. There continues to be debate about the utility of chemotherapy for stage II disease. Without chemotherapy, stage IIb patients have worse 5-year survival than stage III patients likely as a result of routine adjuvant therapy in the stage III patients. However, multiple trials and large database outcomes studies were unable to demonstrate improved survival in stage II patients treated with adjuvant chemotherapy with the exception of QUASAR, a 2007 European randomized trial, which did showed a modest improvement in survival. A Cochrane review including all these patients showed an improved disease free survival but no difference in overall survival. The current thinking is that there is a subset of patients who will benefit from treatment. The NCCN guidelines recommend adjuvant chemotherapy for patients with high risk stage II disease (including T4 tumors, poor differentiation, high grade, perineural or lymphovascular invasion, obstruction, perforation, close or positive margins, or inadequate lymphadenectomy) and consideration of limited treatment of low risk patients. In addition, there is evidence that patients with MSI have a better overall prognosis and are resistant to 5-FU-based chemotherapies. Several trials are in progress to address these areas of uncertainty.
Chemotherapy is the mainstay of treatment for patients with stage IV disease or otherwise unresectable colon cancers. Although a minority of patients with metastatic disease will be candidates for surgical resection, chemotherapy is used in the perioperative period to treat microsocpic foci of disease or in an effort to convert unresectable disease to resectable disease. There is also data to suggest that response to chemotherapy can be used to identify patients who will benefit from surgical metastasectomy. These patients are treated with a chemotherapy regimen similar to patients with stage III disease,with the possible addition of irinotecan and/or a VEG-F inhibitor such as bevacizumab.
TREATMENT OF RECTAL CANCER
Surgery
The choice of operation for rectal cancer depends on many factors. These include the location of the lesion, the depth of penetration and local invasion, histological features such as degree of differentiation and the presence of lymphovascular invasion, and the patient’s individual anatomy, general condition, and preoperative bowel function.
The surgical management of rectal cancer differs from colon cancer for many reasons, mostly related to its unique anatomy. One aspect of rectal cancer that differentiates it from colon cancer is its accessibility. Very early stage rectal cancers can be treated with LE. This involves resection of a full thickness segment of the rectal wall transanally for distal lesions that are within reach. Transanal endoscopic microsurgery is used for more proximal rectal lesions. This utilizes a specialized proctoscope that allows passage of dissecting instruments and insufflation with carbon dioxide. The resection must involve at least 1 cm margins around the circumference of the tumor and the deep margin must be free. This technique does not sample or treat nodal disease and thus should be limited to a select group of patients at low risk for nodal metastasis. Appropriate patients include those with mobile tumors less than 3 cm in size and that extend less than one-third of the circumference of the rectum. They should be histologically low grade, extend only to the mucosa or submucosa (Tis, T1) and have no radiographic or clinical evidence of nodal metastasis.
The T stage is an important predictor of outcome following local excision (LE). LE was initially offered for all patients with stage I disease, however, the local recurrence rates were found to be unacceptably high (up to 47%) with patients with T2 lesions. Therefore, this therapy is generally reserved for patients with T1 disease, where the local recurrence rate is 5%-18%. There is a newer body of literature suggesting that patients with T1 lesions invading to the outer third of the submucosa have a higher risk for recurrence. If pathological analysis reveals a T2 lesion, positive margins, or high risk features, consideration should be given to radical resection (low anterior resection [LAR] or abdominoperineal resection [APR]) or adjuvant chemoradiation due to the higher risk for lymph node metastases. There is preliminary data that patients who are downstaged using neoadjuvant therapy may be appropriate for this procedure as well but this is not yet standard care.
The initial choice of operation is important, because patients who recur tend to present with advanced disease. Only 50% of patients with recurrent disease after LE will be candidates for radical resection and their overall survival is poorer than that of patients who initially undergo radical resection. The advantages of LE include decreased morbidity and mortality, short recovery, and in some cases, the opportunity to avoid a colostomy.
When radical excision of a rectal tumor is considered, planning must include assessment of resection for adequate margins, preoperative bowel function, and patient preference while minimizing morbidity. These procedures have a perioperative mortality of 2%. The options include low anterior resection (LAR) or abdominoperineal resection (APR), which includes a permanent colostomy. For cancers in the distal third of the rectum, an ability to achieve a distal margin of 1-2 cm and negative radial margins with complete mesorectal excision is considered the minimum needed to proceed with LAR. Therefore, tumors at the dentate line, with extramural spread to involve the sphincter complex, or direct extension into pelvic structures, require APR. Restoring intestinal continuity is generally considered best when possible from an oncologic standpoint. However, the more distal the anastomosis, the more postoperative bowel function is affected after resection of the rectum. Therefore, a careful evaluation of the patient’s preoperative bowel function as well as a discussion with the patient about lifestyle changes is an important aspect of surgical planning.
Historically, recurrence rates were high and survival was low for rectal cancers, however, this has been greatly improved with the technique of total mesorectal excision (TME) and the use of neoadjuvant chemoradiation. TME has dramatically reduced local recurrence rates from 15%-40% to 4%-11% and increased survival in patients without metastatic disease. It generally requires full mobilization of the rectum with en block removal of the mesorectum and bowel wall 5 cm distal to the tumor (tumor-specific TME) if the tumor is in the upper rectum, or completely (TME) if the tumor is in the mid- to distal rectum. It requires dissection posteriorly in the avascular plane between Waldeyer’s fascia and the presacral fascia, laterally to encompass the peritoneal reflection but medial to the hypogastric plexus, and anteriorly to include Denonvilliers fascia (Figure 30–11). TME is completed by extending the dissection inferiorly to the levators. This allows removal of the mesorectum en block with the rectum and ensures adequate lymph node removal. Further, it removes any tumor that has perineural spread or direct extension outside of the rectum. It is one of the major principles of both LAR and APR.
Figure 30–11. Total mesorectal excision as depicted in Heald’s original publication.
The laparoscopic approach to rectal tumors is attractive from the standpoint of increasing exposure in the pelvis and minimizing morbidity and length of stay. This approach is associated with earlier return of bowel function and decreased analgesic requirement, although operative time is generally longer. Multiple trials have shown no difference in overall survival or local recurrence rates with follow up extending beyond 5 years.
Because LAR and APR are major operations with extensive pelvic dissection in an often radiated field, the morbidity is higher than colon cancer operations. In addition, LAR includes a technically challenging low anastomosis. Concerns are anastomotic leak, anterior resection syndrome (bowel dysfunction), urinary and sexual dysfunction, wound infection, anastomotic stricture, and injury to the ureters. In cases where identification of the ureters is expected to be difficult, that is, obese patients, those with previous pelvic surgery, and those who have undergoing neoadjuvant chemoradiation, preoperative stent placement can assist with intraoperative identification and preservation of the ureters.
Temporary diversion of the fecal stream is used to protect the colorectal anastomosis in LAR. This is particularly important in patients who are considered higher risk, including those undergoing neoadjuvant chemoradiation or with a very low anastomosis. Diversion significantly reduces the risk of anastomotic leak and need for reoperation. Both loop ileostomy and colostomy are used. Loop ileostomy is favored as it results in fewer stoma complications including prolapse and sepsis, although this method is associated with a higher risk for dehydration and anastomotic stenosis after closure.
Anastomotic leak occurs in 11% of patients undergoing LAR. Patients at greatest risk for anastomotic leak include elderly patients with low anastomoses and neoadjuvant chemoradiation who were not diverted. Some reports cite patient factors such as male sex, older age, smoking, obesity, and medical comorbidities such as renal failure. The type of anastomosis has not been shown to affect the leak rate. Prophylactic drainage has not been shown to alter the postoperative mortality, clinical or radiological leak rates, wound infection, or need for reoperation.
The Anterior Resection Syndrome occurs in 10%-30% of patients after sphincter preserving operations for rectal cancer and is more pronounced the more distal the anastomosis. Symptoms include clustering (frequent bowel movements in a short period of time), urgency, and incontinence to gas, stool, or both. These symptoms can have a significant impact on quality of life and are likely related to colonic dysmotility, neorectal reservoir dysfunction, sphincter complex damage, and aberrant anal canal sensation. It is worse in patients with a history of pelvic irradiation, rectal prolapse, or anorectal surgery. Most patients have improvement of their symptoms with time, and by 6-9 months after surgery, have a decreased, more manageable number of bowel movements per day. Loperamide, fiber supplementation, and biofeedback are useful adjunctive therapies. Loperamide has the benefit of increasing sphincter tone and slowing stool transit. In patients with intractable incontinence, a permanent stoma may be required.
Because LAR and APR involve wide dissection in the pelvis, the postoperative complications include those associated with disruption of the pelvic nerves. Urinary dysfunction, specifically urinary retention is reported in 3%-15% of patients, but this is generally transient. Sexual dysfunction tends to become progressively worse with time. In a recent large survey-based analysis, more than half of men experienced erectile dysfunction and two-thirds experienced problems with ejaculation. One-third of women reported dyspareunia. These factors are also likely related to pelvic irradiation.
Palliative Procedures
If a rectal cancer is unresectable after neoadjuvant therapy, palliative surgery may be indicated to improve symptoms including obstruction, bleeding, or tenesmus. Obstructing cancers can be treated with diversion or endoluminal stents, however, there is a high risk of stent occlusion and perforation. Bleeding and tenesmus may be responsive to fulguration or photocoagulation, although outcomes have been disappointing.
Chemotherapy and Radiation
Stage I rectal cancers are adequately treated with surgical excision. However, stage II and stage III rectal cancers have high local recurrence rates. Combined-modality therapy including preoperative chemoradiation, surgery, and adjuvant chemotherapy has been shown to increase survival in these patients. Standard neoadjuvant treatment uses 5-FU as a radiosensitizer. Compared with postoperative chemoradiation, neoadjuvant treatment has been shown to decrease local recurrence and toxicity and increase sphincter preservation. However, it has not been shown to improve overall survival. Twenty percent of patients will have a complete pathologic response which is associated with improved survival. Surgery is planned 4-10 weeks after the completion of treatment. Following resection, adjuvant therapy with FOLFOX or capecitabine is standard, although trials are in progress to determine the optimal duration of treatment.
METASTATIC DISEASE
Metastatic disease is reported in 20% of patients with CRC at presentation and up to 30%-70% of patients will eventually be found to have metastasis. The two most common locations are the liver and the lung. Untreated, these patients have a 5-year survival of 5%. However, selected patients are candidates for surgical resection with curative intent. Surgery results in an improved 5-year survival of 22%-49% for patients with metastatic disease in the liver and 14%-78% for patients with lung disease. If both liver and lung disease are treated surgically, 5-year survival is 30%. After surgery for metastatic disease, 50%-70% of patients have a subsequent recurrence.
Liver and lung metastases are considered resectable if they, and all other sites of disease, including the primary tumor, are amenable to a R0 resection. This is based on the anatomic location as well as leaving an adequate quantity of normal tissue to maintain normal function. Options for patients with extensive disease include preoperative portal vein embolization or staged resection. There are reports of patients being treated with ablative therapies (microwave, radiofrequency) or external beam radiation; however, there are no long-term data available for these procedures. If metastatic disease in the liver initially appears unresectable, induction chemotherapy will result in a clinical response allowing resection in 16% of patients. If metastatic disease recurs after treatment, re-resection is considered in selected patients.
Peritoneal metastasis generally results in poor outcomes with median overall survival of 5-24 months. Current guidelines recommend chemotherapy as the primary treatment. Investigational treatments such as cytoreductive surgery and intraperitoneal chemotherapy show promise in improving survival, however these treatments are associated with significant morbidity and mortality and are not considered standard of care.
POSTOPERATIVE SURVEILLANCE
The goal of postoperative surveillance is to measure the efficacy of treatment and to diagnose recurrences, metastases, and metachronous lesions. After appropriate treatment for CRC, one-third to one-half of patients will recur. The majority of these (60%-80%) will be in the first 2 years and 90% in the first 5 years after surgery. Three percent will develop a new metachronous tumor by 6 years.
Seventy-five patients with recurrent CRC will have an elevated CEA. Using a cutoff of 6 IU/L yields a sensitivity of 80% and specificity of 42%. It is most sensitive for detection of metastatic disease in the liver, and is elevated months before symptoms appear. Although less sensitive, CT of the abdomen has a similar benefit. Earlier detection improves resectability and survival. If the CEA is elevated, PET scanning is a useful adjunct to the evaluation as it has been shown to have better sensitivity and specificity for recurrent disease than CT.
After many well-designed randomized trials, there is still no consensus on what constitutes appropriate follow up for treated CRC patients. The 2012 NCCN guidelines suggest a history, physical examination, and CEA every 3-6 months. In addition, patients with high risk features such as lymphovascular invasion or poorly differentiated tumors should undergo CT of the chest, abdomen, and pelvis every year for 3-5 years. Colonoscopy should be performed at 1 year, and if normal, subsequent examinations should be scheduled in 3 years, and then every 5 years. For patients with rectal cancer who underwent LAR, proctoscopy should be considered every 6 months for 5 years. Although cost-effectiveness and survival benefit has been suggested for these surveillance strategies, they have not been proven definitively. However, they do increase the possibility of treating recurrences with intent for cure.
Treatment for Recurrent Disease
CRC recurs in up to 50% of patients. In patients with rectal cancer, 35% will have a local recurrence compared with 15% of patients with colon cancer. Otherwise, the most common sites are the liver, lung, and regional lymph nodes. If R0 resection is possible, this can be undertaken in patients who are good surgical candidates in combination with adjuvant chemotherapy. In patients who present with unresectable disease, a combination of palliative chemotherapy and radiation therapy (if appropriate based on location) is administered, although this is unlikely to improve survival. However, the overall prognosis for recurrent CRC is poor. Survival is 35% at 5 years in patients who are candidates for curative surgical resection.
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OTHER TUMORS OF THE COLON & RECTUM
Neuroendocrine Tumors
Neuroendocrine tumors (NETs), or carcinoids, of the colon and rectum account for approximately 6% of all NETs of the gastrointestinal tract. They are rare, although the incidence is increasing. More than half are found in the rectum. Incidence is increased in patients with IBD. They are rarely symptomatic and are most often diagnosed during screening colonoscopy or incidentally during laparotomy or imaging for other conditions.
Although the prognosis for these tumors is largely undefined because of their rarity, important factors include histologic subtype, tumor size, depth of invasion, and location. They are classified as benign (previously typical carcinoid), low grade malignant (atypical carcinoid), or high grade malignant (small and large cell carcinoma) and are staged according to the tumor, node, metastasis (TNM) system. Survival for rectal carcinoids is better than colon carcinoids, which tend to be associated with colon adenocarcinoma. Benign and low-grade malignant tumors are best managed surgically. There is controversy over the extent of surgery required, but it has been suggested that tumors greater than 1-2 cm or with high-risk histological features are best treated with standard oncologic resection whereas smaller lesions can be managed with local excision. High-grade malignant carcinoids of the large intestine are extremely aggressive and have a poor prognosis even if diagnosed at an early stage. These are best treated with chemotherapy.
Lymphomas
The most common site of extranodal non-Hodgkin lymphoma is the gastrointestinal system; however, the colon and rectum are rarely affected. This disease is more common in middle-aged men and immunosuppressed patients. Symptoms are generally nonspecific, and more than half of patients present with a palpable abdominal mass. On imaging it appears as an infiltrating submucosal lesion with associated mesenteric lymphadenopathy, making it difficult to discern from adenocarcinoma. Another form, lymphomatous polyposis, can mimic familial polyposis coli. Colonoscopy with biopsy is important because depending on the subtype of lymphoma, chemotherapy and/or radiation is the primary treatment. Because the diagnosis is often delayed, patients may need urgent or emergent surgery for acutely symptomatic lesions.
Lipomas
The colon is the most frequent site of gastrointestinal lipomas. They are benign fatty submucosal tumors with an incidence of 1%-4%. They are more common in women and in the right colon. Lipomas are generally asymptomatic, however, they may cause vague abdominal symptoms or intussusception, especially if large in size. Although they can sometimes be difficult to differentiate from colon malignancy, the diagnosis can be made by characteristic findings on endoscopic ultrasound (hyperechoic submucosal lesion). Resection is indicated for symptomatic lipomas or if the diagnosis is not clear by radiographic or endoscopic findings.
GASTROINTESTINAL STROMAL TUMORS
Gastrointestinal stromal tumors (GISTs) are derived from the pluripotential interstitial cells of Cajal and are associated with activating mutations in a specific tyrosine kinase found in the large intestine called KIT or CD 117. Like many of the aforementioned neoplasms, these are submucosal tumors that can grow to a large size before causing symptoms. They are commonly diagnosed radiographically, although occasionally percutaneous or endoscopic biopsy is necessary to confirm or rule out metastatic disease for treatment planning purposes. Surgery is the standard treatment for patients with localized tumors > 2 cm, tumors with high risk features, or symptomatic tumors. Because GISTs spread hematogeneously, local resection with negative margins is adequate. Care must be taken to prevent intraoperative rupture of the tumor pseudocapsule as this is associated with high rates of recurrence. Medical therapy with imatinib mesylate, which selectively inhibits KIT is used for patients with unresectable tumors, metastatic disease, or poor prognostic factors. Sunitinib malate has been introduced as salvage therapy for patients with imatinib-resistant disease. Prognostic factors include location in the GI tract (stomach most favorable), mitotic index, and size. They are associated with generally good overall survival but recurrence is common.
ENDOMETRIOMAS
Endometriosis refers to the presence of endometrial tissue that forms implants in the pelvis and abdomen. Deeply infiltrating endometriosis refers to a subtype with locally invasive implants on the bowel wall. Symptoms include abdominal pain, hematochezia, and pain with defecation. Most patients present with palpable, tender nodules on rectal or vaginal examination. The diagnosis is made endoscopically in most patients. Medical management with NSAIDs, oral contraceptives, and GnRH agonists is generally limited by side effects and does not appear to prevent progression of the disease. Surgery is indicated for persistent symptoms or if malignancy cannot be excluded. The implants are treated with superficial excision, full thickness excision with primary defect closure, and resection with anastomosis. Although early reports cited concern over the development of anastomotic leak and rectovaginal fistulas, these complications have proven to be rare. While the majority of patients experience symptomatic improvement, recurrence is over 10% and long-term follow-up is lacking.
OTHER TUMORS
Other rare tumors of the large intestine have been reported, including neurofibromas, teratomas, rectal duplication cysts, lymphangiomas, and cavernous hemangiomas. Rare malignancies include adenosquamous carcinoma, primary squamous cell carcinoma, and melanoma.
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DIVERTICULAR DISEASE OF THE COLON
DIVERTICULOSIS
General Considerations
Diverticula (singular: diverticulum) are more common in the colon than in any other portion of the gastrointestinal tract. Their presence is referred to as diverticulosis. Most colonic diverticula are false, referring to the fact that they consist of mucosa and submucosa that have herniated through the muscular layer of the colon wall. True diverticula, which contain all layers of the bowel wall, are rare in the colon. In the United States, the most common location for diverticula is the sigmoid colon. The descending, transverse, and ascending portions of the colon are involved in decreasing order of frequency. Diverticula form as a result of increased intraluminal pressure acting at areas of relative weakness on the bowel wall caused by the blood supply. The vasa recta extend onto the colon wall, then penetrate the muscular layer between the taenia to supply the mucosa. Therefore, diverticula are most commonly located in the area between the mesenteric taenia and the antimesenteric taenia with a skip area on the antimesenteric border (Figure 30–12).
Figure 30–12. Cross-section of the colon depicting the sites where diverticula form. Note that the antimesocolic portion is spared. The longitudinal layer of muscle completely encircles the bowel and is not limited to the taeniae as depicted here.
Epidemiology
In Western countries, 30%-60% of individuals develop diverticula. There is no gender predilection. The prevalence increases with age, although recently there has been an increase in the younger population. Ten percent of patients are affected by age 40 and 65% by age 80. Diverticular disease is more common in Western nations. In Asian countries, there is a predominance of right-sided diverticula. The geologic differences in the incidence of diverticular disease suggest that cultural factors may play an etiologic role. The contribution of a low fiber diet rich in red meat is a commonly cited risk factor but this has not been shown conclusively. Other reported factors include physical inactivity, constipation, increasing age, smoking, obesity, alcohol, and NSAID use. Patients with Ehlers–Danlos and Marfan syndrome, both of which involve abnormal connective tissue, are at increased risk.
Symptoms and Signs
Diverticulosis remains asymptomatic in up to 80% of people and is usually detected incidentally on barium enema x-ray, CT scan, or colonoscopy. A history of constipation is often elicited. An abdominal examination may reveal mild tenderness in the left-lower quadrant, and the left colon is sometimes palpable as a firm tubular structure.
Treatment
Asymptomatic patients with diverticulosis may be given a high-fiber diet, although its role is unclear except as a treatment for constipation. There is no evidence to suggest that avoiding nuts, seeds, or popcorn has a protective effect. In fact, no dietary change has been conclusively shown to treat diverticulosis or prevent its complications, although weight loss, smoking cessation, and a diet low in red meat have been suggested as possibilities. Surgery is not indicated for uncomplicated diverticulosis.
Prognosis
The natural history of diverticulosis has not been defined. Complications of diverticulosis including diverticulitis, hemorrhage, stricture, and fistula formation occur in approximately 20% of patients with diverticulosis. Because these estimates rely on patients with known diverticulosis, the incidence of complications in the general population (who have undiagnosed, asymptomatic diverticulosis) may be much lower. About 75% of patients who present with complications of diverticular disease report no prior colonic symptoms.
DIVERTICULITIS
General Considerations
Acute diverticulitis is the result of micro- or macroscopic perforation of a diverticulum resulting in an inflammatory response. The sigmoid colon is the most common location for diverticula and therefore is the most common location of diverticulitis. The severity of disease can range from mild inflammation localized to a segment of the bowel wall (microperforation) to feculent peritonitis (macroperforation). The majority of patients (75%) present with simple, uncomplicated, diverticulitis. This occurs when microperforation is immediately walled off, resulting in localized inflammation. Complicated diverticulitis occurs in 25% of patients and refers to macro- or gross perforation with abscess or peritonitis, as well as those who develop complications including stricture or fistula.
Clinical Findings
Patients with acute diverticulitis classically present with abdominal pain and fullness localized to the left-lower quadrant. The average age of presentation is 62 years. The severity of abdominal pain ranges from mild to severe, often described as steady aching or cramping. It often resembles acute appendicitis except that it is situated in the left-lower quadrant. Occasionally, pain is suprapubic, in the right-lower quadrant, or throughout the lower abdomen depending on the location of the sigmoid and the distribution of disease. Changes in bowel habits, including constipation, diarrhea, or both are common. Dysuria is indicative of inflammation adjacent to the bladder. Nausea and vomiting may be present depending on the location and severity of the inflammation. Physical findings characteristically include low-grade fever, mild abdominal distention, and left-lower quadrant tenderness. There may be a palpable mass. Leukocytosis is common.
Acute diverticulitis can also present with other nontypical symptoms. Small bowel obstruction may occur if a loop of small bowel becomes entrapped in inflammatory tissue. Free perforation of a diverticulum can result in generalized peritonitis rather than localized inflammation. Episodes of recurrent diverticulitis may produce mild symptoms until a complication such as stricture or fistula develops that prompts the patient to seek medical attention. The course of diverticulitis may be insidious, particularly in the elderly. Patients may present with vague abdominal pain associated with an abscess or recurrent urinary tract infections from a colovesical fistula. In some cases, pain and inflammatory signs are not marked, but a palpable mass and signs of large bowel obstruction are present, so that carcinoma of the left colon seems the more likely. Diagnosing malignancy can be difficult in the setting of inflammation.
Plain abdominal films are generally not useful unless they show free abdominal air from a diverticulum that has perforated. Other nonspecific findings include ileus, partial colonic obstruction, or left-lower quadrant mass.
CT scan of the abdomen and pelvis with intravenous contrast is the preferred initial imaging study. In most studies, CT has sensitivity, specificity, and accuracy greater than 90%, although 5% of patients will ultimately be found to have cancer as the underlying cause. It is also helpful to rule out other intra-abdominal pathology that may present in a similar fashion. Findings include wall thickening, fat stranding, and diverticula. Complications such as abscess or fistula may be evident (Figure 30–13). Findings on CT scan may also be predictive of the need for surgical intervention or successful nonoperative expectant management. The Hinchey classification was developed in 1978 to help guide clinical decision making for patients with complicated disease and standardize radiographic reporting. These have been updated to reflect improved resolution of CT and currently include the following stages: (0) mild clinical diverticulitis; (1a) pericolic inflammation or phlegmon; (1b) pericolic or mesocolic abscess; (2) pelvic, intra-abdominal, or retroperitoneal abscess resulting from an extension of a pericolic abscess; (3) purulent peritonitis; and (4) feculent peritonitis.
Figure 30–13. CT scan showing sigmoid colon involved with diverticulitis. Note the pericolonic stranding, bowel wall thickening, and intramural abscess.
Colonoscopy is not needed for the evaluation of a patient presenting with classic signs, symptoms, and imaging. However, differentiating acute diverticulitis from other pathology such as IBD, carcinoma, and ischemic colitis can be difficult. If endoscopy is determined to be necessary for appropriate management, a delayed examination after inflammation has subsided is preferred. If timing is critical, then a sigmoidoscopy with low insufflation is recommended over colonscopy to reduce the risk of perforation.
Differential Diagnosis
Acute diverticulitis presents with such variation that the differential diagnosis is broad. It may simulate appendicitis, perforated colonic carcinoma, obstruction with strangulation, colonic ischemia, Crohn disease, cystitis, infectious colitis, and gynecologic disease such as pelvic inflammatory disease, tubal pregnancy, and tubo-ovarian abscess. Differentiation from appendicitis is especially difficult when a redundant sigmoid colon lies in the right-lower quadrant. Free perforation with generalized peritonitis is difficult to differentiate from the other causes of perforation. A thorough history and physical examination as well as imaging studies may be helpful in differentiating these conditions. Colonoscopy is usually deferred upon initial presentation of suspected acute diverticulitis, but may be useful in cases with a high suspicion of carcinoma, vascular insufficiency, or inflammatory disease of the colon. It can be difficult in some cases to rule out carcinoma of the colon, particularly in the more silent forms of diverticulitis that present with a mass or fistula. Occasionally the diagnosis may not be known until the surgical specimen is examined by the pathologist.
Complications
The clinical spectrum of diverticulitis includes complications such as free perforation, abscess, fistula, and obstruction. Fecal peritonitis requires immediate surgery. Abscesses can often be drained percutaneously. Fistulas most commonly involve the bladder or colon, but may also extend to involve the ureter, urethra, vagina, uterus, small bowel, ovaries, fallopian tubes, perineum, and abdominal wall. Colonic obstruction is usually slow in onset and incomplete. Small bowel obstruction may result from inflammatory involvement of the small bowel.
Treatment
Approximately 80% of patients with mild acute diverticulitis (Hinchey 0 and Ia) can be managed on an outpatient basis. However, hospitalization should be considered in patients with mild attacks if they are elderly, immunosuppressed, or have significant comorbidities including diabetes or renal failure. Any patient will need inpatient treatment if there is significant pain, inability to tolerate oral intake, or there is evidence of severe systemic illness. Patients not requiring hospitalization are generally treated with a clear liquid diet, broad spectrum antibiotics (ciprofloxacin and metronidazole or amoxicillin-clavulanate), and close follow up, although this management strategy is largely historical and is being challenged. There is evidence that patients with uncomplicated diverticulitis do not require antibiotics. A recent trial showed no difference in hospital stay, development of complications, or recurrence within 1 year. Patients who were pregnant, immunosuppressed, or septic were excluded.
For those patients requiring hospitalization, treatment depends on the severity of presentation. Generally, patients are managed with bowel rest, intravenous fluids, and systemic broad-spectrum antibiotics. Common regimens cover colonic flora and are chosen based on the patient’s allergies and previous antibiotic exposure. Common regimens include a beta-lactam/beta-lactamase inhibitor, a carbapenem, or the combination of a fluoroquinolone plus metronidazole. As clinical manifestations resolve, oral feeding is resumed gradually, initially with a low residue diet. After recovery, a high fiber diet is prescribed if there is no stricture, although this intervention has not been shown conclusively to reduce recurrence. Conservative management is successful in up to 85% of patients. Repeat CT or intervention is indicated when patients fail to improve or if there is clinical deterioration over the initial 48 hours of medical therapy. This often indicates progression to complicated disease that may require surgery.
Over the last decade, more and more patients are being managed conservatively, which has prompted study into strategies to prevent subsequent episodes. Small randomized trials have been conducted on patients who developed diverticulitis twice in 1 year. Mesalamine and rifaximin taken at 1 week intervals every month decreased symptoms and recurrence compared with rifaximin alone. Two small trials of probiotics have shown no significant improvement. However, it has been shown that avoidance of nuts, popcorn and seeds does not reduce the risk of diverticulitis and thus, patients do not need to be counseled to do so.
Interventional Management
Patients with diverticulitis complicated by phlegmon or small abscess without peritonitis (Hinchey Ib) are candidates for conservative treatment. However, large abscesses (> 3 cm) are less likely to resolve with conservative management and should be drained percutaneously if possible. This provides source control and generally results in clinical improvement within days. Percutaneous treatment of an intra-abdominal abscess allows surgical intervention to be performed on an elective basis when there is reduced risk of complications and higher probability of a one-stage operation without a stoma.
Surgical Management
Recent studies examining the natural history of diverticulitis have demonstrated that over a period of 10 years, recurrent diverticulitis following nonoperative management is expected in 10%-30% of patients. In patients who have a recurrence, a similar proportion will have a third episode. Recurrences tend to occur with similar severity of the previous episode and patients who require urgent surgery usually do so during the first presentation. In other words, it is rare for a patient with a recurrence to require urgent surgery. This indicates a generally benign course for uncomplicated diverticulitis and calls into question the potential benefits of elective prophylactic surgery for patients with a history of acute diverticulitis.
In addition, elective sigmoid colectomy is not without risks. A retrospective review found that 20% of patients experience fecal incontinence, urgency, or incomplete evacuation after sigmoid resection for diverticulitis. The exact indications for surgery have yet to be defined, but overall there has been a general decrease in elective colon resections for diverticulitis in the past 10 years. The American Society of Colon and Rectal Surgeons (ASCRS) guidelines recommend that surgery is offered on an individual basis. Consideration should be given to the patient’s previous episodes, frailty, reliability, and access to medical resources. Surgery is generally reserved for complicated disease such as abscess, perforation, stricture, fistula, or high risk patients such as those who are immunologically suppressed. Surgery should also be considered in patients in whom an underlying cancer cannot be excluded.
When interval colectomy is recommended, it is generally delayed by 6-8 weeks to allow resolution of acute inflammation that may add difficulty to the operation. There is evidence that delaying surgery increases the rate of a successful laparoscopic resection with primary anastomosis, which is possible in more than 90% of patients. However, delaying surgery comes with the small but significant risk (2%) of interval development of recurrent severe diverticulitis requiring emergency surgery with high morbidity. Further study is required to determine the optimal timing of surgery.
Definitive resection for sigmoid diverticulitis should include the sigmoid colon distally to the uninvolved rectum. The proximal extent of resection should be the point at which the bowel is soft and appears healthy—this generally includes the entire sigmoid colon. It is unnecessary to resect additional bowel proximally; even if it is involved with diverticula, as they are unlikely to become symptomatic (Figure 30–6). Laparoscopy has been shown in randomized trials to decrease hospital stay and postoperative pain without increased complications; however, it is a technically challenging operation that should be undertaken only by surgeons comfortable with the technique. In some cases, even in experienced centers, laparoscopy may not be possible due to persistent inflammation and an open approach is required.
A subset of patients will present with colonic stricture as a result of chronic inflammation and scarring. This generally results in symptoms of partial obstruction. If an inflammatory stricture is diagnosed after radiographic and endoscopic evaluation, elective resection is recommended. The distal extent of resection should always include the rectosigmoid junction so that the proximal colon is anastomosed to healthy proximal rectum.
Less than 10% of patients will present with complications requiring urgent surgery. Indications include uncontrolled sepsis and failure to improve with medical therapy or percutaneous drainage. There is a lower threshold for surgery for immunocompromised patients given their greater risk of morbidity and mortality with medical management. These are generally features found in patients with Hinchey III or IV disease.
At laparotomy for severe acute diverticulitis, exploration may reveal an inflammatory mass involving large bowel, mesocolon, mesentery, omentum, and sometimes small bowel. Except in cases of free perforation with generalized fecal peritonitis, the diseased diverticulum is not often visible. The type of operation performed is dependent on the extent of colonic inflammation, the amount of peritonitis, the patient’s general condition, comorbidities, and nutritional status, the extent of blood loss, and the surgeon’s experience and preference.
Ideally, a resection with primary anastomosis is performed as a one-stage procedure. It may not be possible to perform a primary anastomosis if there is gross contamination or infection in the surgical field because of the increased risk of anastomotic leakage. In patients who can tolerate an anastomosis but are still considered high risk, a diverting loop ileostomy is an option.
However, if the risk of an anastomosis is perceived to be too high, two options are available. The standard is the Hartmann procedure, which is a two-stage operation. At the initial operation, the diseased bowel is removed, the proximal end of the colon is brought out as a temporary colostomy, and the distal colonic stump is closed (Figure 30–6). Intestinal continuity is restored in a second operation after the inflammation subsides. There have been reports in the literature of Hinchey III patients having laparoscopic washout and drainage without resection as an alternative to resection. This approach has not been widely adopted and a randomized controlled trial is currently underway to compare this approach with the Hartmann procedure. Increasingly, percutaneous drainage of abscesses avoids the need for staged procedures and allows for primary resection with anastomosis once the inflammation has resolved. However, if percutaneous drainage is unsuccessful, operative drainage is indicated.
A three stage procedure, consisting of diversion and washout followed by resection of the diseased bowel at a second operation, and finally colostomy takedown, is not advised due to the ongoing inflammation of the diseased bowel and associated morbidity despite fecal diversion. However, if the patient will not tolerate a resection, this is an option.
Follow-Up
Colonoscopy is recommended 6-8 weeks after the resolution of symptoms and prior to elective surgical resection to rule out other underlying pathology such as IBD and cancer. Although the presence of malignancy is less than 5% in patients with a radiographic diagnosis of acute diverticulitis, it is especially important to exclude malignancy in the presence of rectal bleeding stricture, or mass. The entire colon should be evaluated prior elective resection for presumed diverticular disease.
Prognosis
The mortality for diverticulitis can be divided by Hinchey stage. Patients with stage I or II disease have a mortality of less than 5%, stage III 13%, and stage IV 43%. Approximately 25% of patients hospitalized with acute diverticulitis require surgical treatment. The operative mortality rate is about 5% in recent reports, compared with 25% historically. Some of this improvement is attributable to the greater use of percutaneous drainage.
Diverticulitis recurs in one-third of patients managed conservatively and in 2%-10% of patients after surgical resection. Most of these recurrences develop within the first 5 years and are most commonly in the rectosigmoid junction due to inadequate resection. More study is required prior to the routine use of mesalamine and probiotics to reduce this risk.
Bachmann K, Krause G, Rawnaq T, et al: Impact of early or delayed elective resection in complicated diverticulitis. World J Gastroenterol 2011 Dec 28;17(48):5274-5279.
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Klarenbeek BR, de Korte N, van der Peet DL, Cuesta MA: Review of current classifications for diverticular disease and a translation into clinical practice. Int J Colorectal Dis 2012 Feb;27(2):207-214.
Levack MM, Savitt LR, Berger DL, et al: Sigmoidectomy syndrome? Patients’ perspectives on the functional outcomes following surgery for diverticulitis. Dis Colon Rectum 2012 Jan;55(1):10-17.
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Rafferty J, Shellito P, Hyman NH, Buie WD: Practice parameters for sigmoid diverticulitis. Dis Colon Rectum Jul 2006;49(7): 939-944.
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Strate LL: Lifestyle factors and the course of diverticular disease. Dig Dis 2012;30(1):35-45.
Unlü C, Daniels L, Vrouenraets BC, Boermeester MA: Systematic review of medical therapy to prevent recurrent diverticulitis. Int J Colorectal Dis 2012 Sep;27(9):1131-1136.
LARGE BOWEL FISTULAE
Colovesical Fistula
Diverticulitis is the etiology of more than half of all colovesical fistulas. This complication occurs in 2%-4% of cases of patients. Other causes include colon cancer, bladder cancer, Crohn colitis, radiation exposure, trauma, and iatrogenic causes. They occur three times more often in men. This predilection is likely anatomical: in women the uterus and adnexa are situated between the colon and the bladder.
The most common presentation is recurrent urinary tract infection. Pneumaturia is reported by up to 70% of patients and fecaluria in up to 50% depending on the size of the fistula. There are no specific physical examination findings, although some patients may have a palpable pelvic mass. There is usually no leukocytosis. Urine analysis is often indicative of urinary tract infection and cultures are polymicrobial. CT of the pelvis with rectal contrast is the most sensitive imaging study and will often show a segment of inflamed colon and bladder wall with air in the bladder. The fistulous connection is rarely seen. Endoscopy and cystoscopy may reveal inflammation at the site of the fistula, but the fistula is rarely visualized. These tests are useful for ruling out malignancy prior to surgical intervention. If the diagnosis is still in question, ingestion of charcoal or poppy seeds with elimination in urine is diagnostic.
The treatment for symptomatic colovesical fistula is elective surgery. The operation should be delayed until any active inflammation (ie, from diverticulitis) has resolved. Up to 50% of colovesical fistulas will undergo spontaneous closure. In these patients, the decision to proceed with surgery depends on the underlying cause of the fistula. In most patients, surgery involves resection of the involved colon with a primary anastomosis. Large bladder fistulas are closed primarily, but most often they do not require closure but are left to close spontaneously with Foley catheter drainage. However, in malignant fistulas, the tract should be excised en block with the colon and the involved bladder wall, which can be repaired primarily. Omentum is interposed between the anastomosis and the bladder. A urinary catheter is used to decompress the bladder for 5-10 days after surgery. The optimal timing of catheter removal or need for urine cultures or cystogram has not been prospectively validated.
In minimally symptomatic patients at high risk for surgery, conservative management with intermittent antibiotics may be successful. A trial of medical management is also indicated in patients with Crohn colitis, in whom spontaneous closure may be possible.
The prognosis for colovesical fistula is related to the etiology and the general health of the patient. Recurrence is reported to be 4%-5% overall, but is highest in patients with fistulas secondary to radiation therapy and Crohn colitis.
Fiocchi C: Closing fistulas in Crohn’s disease–should the accent be on maintenance or safety? N Engl J Med Feb 26 2004;350(9): 934-936.
Leicht W, Thomas C, Thüroff J, Roos F: Colovesical fistula caused by diverticulitis of the sigmoid colon : diagnosis and treatment. Urologe A 2012 Jul;51(7):971-974. [Translated to English]
Lynn ET, Ranasinghe NE, Dallas KB, Divino CM: Management and outcomes of colovesical fistula repair. Am Surg 2012 May;78(5):514-518.
RECTOVAGINAL & COLOVAGINAL FISTULA
Colovaginal fistulae are commonly a complication of diverticulitis, especially in women with a history of hysterectomy. The most common cause of rectovaginal fistula is obstetric injury, followed by Crohn colitis, iatrogenic causes, malignancy, radiation, and trauma. Fistula between the lower third of the rectum and lower half of the vagina are classified as low rectovaginal fistulas, while high fistula are defined as those between the middle to upper third of the rectum and the posterior vaginal fornix. The most common presentation is feculent vaginal discharge, which may be mistaken for fecal incontinence. Patients may also report vaginal flatus, recurrent genitourinary infections, and dyspareunia. There is a significant negative impact on quality of life. A fistula may be observed on anoscopy, rigid sigmoidoscopy, and/or vaginal speculum examination in 85% of patients. Endorectal ultrasound (ERUS), CT with rectal contrast, or barium enema may confirm the diagnosis.
The treatment for recto- and colovaginal fistula is surgical. Colovaginal fistulas are often successfully managed with resection of the involved colon. The vaginal defect may be closed, but will generally close spontaneously if this is technically challenging. The optimal surgical treatment for rectovaginal fistula, on the other hand, is less clear. The treatment is largely based on etiology, individual patient factors and surgeon experience. Numerous procedures have been reported, including direct repair, fibrin glue, endorectal advancement flaps, vaginal advancement flaps, biologic mesh, tissue interposition, and rectal resection. Choice of repair depends on the etiology, size, and location of the fistula. However, the recurrence rate is disappointingly high, especially for patients with Crohn disease who have an ongoing source of inflammation. The optimal approach consists of aggressive medical treatment of the colitis and control of pelvic sepsis followed by surgery. However, reported recurrence rates are 25%-50%. Good results have been reported in patients with multiple recurrences using fecal diversion and repair with a gracilis or omental interposition flap or even proctectomy with permanent stoma.
Ruffolo C, Scarpa M, Bassi N, Angriman I: A systematic review on advancement flaps for rectovaginal fistula in Crohn’s disease: transrectal vs transvaginal approach. Colorectal Dis 2010 Dec;12(12):1183-1191.
van der Hagen SJ, Soeters PB, Baeten CG, van Gemert WG: Laparoscopic fistula excision and omentoplasty for high rectovaginal fistulas: a prospective study of 40 patients. Int J Colorectal Dis 2011 Nov;26(11):1463-1467.
Zhu YF, Tao GQ, Zhou N, Xiang C: Current treatment of rectovaginal fistula in Crohn’s disease. World J Gastroenterol 2011 Feb 28;17(8):963-967.
ACUTE LOWER GASTROINTESTINAL BLEEDING
Background
Lower gastrointestinal bleeding refers to bleeding originating distal to the ligament of Treitz and involves the small bowel, colon, or rectum. Unlike upper GI bleeds, it occurs in predominantly elderly patients. It accounts for 20% of all GI bleeds and results in over 300,000 hospitalizations in the United States each year. The incidence appears to be increasing with time. Hematochezia refers to the passage of bright red blood, maroon blood, or clots per rectum. Classically, hematochezia indicates a lower GI source of bleeding, however, the color is a function of time spent in the intestinal tract. The black color of melena is the result of the oxidation of iron in hemoglobin. Bright red blood may stem from brisk esophageal variceal bleeding and melena may be the result of slow blood loss from a right-sided colon cancer.
Etiology
Lower GI bleeding can originate from numerous sources. In elderly patients common causes include diverticula, angiodysplasia, malignancy, and ischemia. Younger patients are more commonly affected by IBD, solitary rectal ulcer, and infection. In the appropriate patient, bleeding may be related to coagulopathy, radiation injury, chemotherapy, or a recent procedure such as polypectomy. Chronic, low volume bleeding is seen in patients with malignancy, polyps, hemorrhoids, and fissures. The small intestine can be the source of bleeding in 5% of patients. Other more unusual causes include Meckel’s diverticulum (especially with ulceration from ectopic gastric mucosa), and aorto-enteric fistula.
Diverticulosis is the most common source of acute lower GI bleeding. Although bleeding occurs in only 5% of patients with diverticulosis, this presentation is common because of the high prevalence of diverticula in the general population. Diverticula form in areas of weakness where vasa recta penetrate the bowel wall. Structural changes in the bowel wall causes damage to the artery, which can lead to rupture. Diverticular bleeding often presents with painless and massive, but self-limited, hemorrhage. There is a dose-related increase in risk in patients who use NSAIDs. The long-term recurrence rate after the first episode is 25%, however, this increases to 50% after the second episode. Therefore surgery is commonly recommended in the elective setting after a patient presents with recurrent bleeding.
Angiodysplasia, or vascular ectasia, is found in 2% of asymptomatic patients on screening colonoscopy. They are generally located in the right colon in elderly patients and the jejunum in younger patients. These lesions are composed of dilated submucosal vessels with a central feeding vein that have a propensity to bleed spontaneously. Bleeding is typically intermittent and low volume. These patients often present in the outpatient setting with iron deficiency anemia and heme-positive stool. The diagnosis is made in some cases by colonoscopy, and colonoscopic therapy is often successful. There is no need to treat incidentally identified ectasias, as it is estimated that only 15% will cause clinically significant bleeding. Surgery is rarely indicated.
Colitis resulting from IBD, ischemia, radiation, or infection is a third cause of hematochezia. These tend to cause mild blood loss rarely requiring transfusion. These should be suspected in patients with abdominal pain and diarrhea. Acute ischemia may be caused by an acute decrease in blood supply from embolism, hypotension, or spasm. The watershed areas, including the splenic flexure and rectosigmoid junction, are most commonly affected. Infectious colitis can be diagnosed by stool culture. The most common organisms causing bloody diarrhea are E coli 0157-H7, Campylobacter, andShigella. UC and Crohn colitis can also cause hematochezia during periods of acute inflammation. UC is more commonly associated with bleeding, although it can sometimes be difficult to distinguish between these two entities during an initial colonoscopy. However, the management in this setting is the same. Treatment with steroids and immunomodulators depends on the severity of the disease. This is discussed further in the section on colitis.
Management
Chronic rectal bleeding, as seen in patients with colorectal polyps or cancer, and anorectal conditions can be evaluated electively. It is important to include colonoscopy in the evaluation, even if the bleeding can be explained by a benign condition such as hemorrhoids. This is especially true for patients who are more than 50 years of age or have a family history of CRC as it ensures that there is not a more proximal lesion that needs to be addressed.
Acute severe hemorrhage, however, is a potentially life-threatening problem, and prompt evaluation and treatment are critical. The first step in the management of these patients is to evaluate and manage the airway, breathing, and circulation (ABCs). A significant portion of these patients present with hemorrhagic shock. Resuscitation with intravenous fluids and blood products takes priority over initiation of diagnostic procedures. Large bore intravenous catheters should be placed and efforts made to keep the patient warm. Strong consideration should be given to transferring the patient to the intensive care unit or other closely monitored setting. Labs are checked for a coagulation profile, platelet count, and hematocrit. Any coagulation abnormalities should be corrected. Patients should be asked about the recent use of antiplatelet agents and blood thinners. Associated medical conditions should be identified and treated as soon as possible. Digital rectal and anoscopic examinations are performed first to look for an obvious source of bleeding and consideration should be given to the possibility of an upper source. A nasogastric aspirate should be examined to rule out an upper source in most patients. While this is not a perfect test, it can provide quick and useful information in a patient with a life threatening upper GI bleed. If blood is aspirated, there is confirmation of an upper source and EGD should be performed. If bile is aspirated, the source is more likely from the lower GI tract and the diagnostic work up should continue. The next step is determined by patient stability and availability.
A plan of management of acute lower gastrointestinal hemorrhage is outlined in Figure 30–14. Many decisions depend on the rate of bleeding, which is difficult to include in an algorithm. Bleeding stops spontaneously in 90% of patients before transfusion requirements exceed two units, but there are no reliable methods to predict who these patients are or who will have recurrent bleeding. Therefore all brisk GI bleeding must be taken seriously.
Figure 30–14. Plan for diagnosis and treatment of acute lower gastrointestinal hemorrhage. (NG = nasogastric)
There are a wide range of procedures that can be used for both diagnostic and treatment purposes in the acute setting. These include endoscopy, angiography, and radiographic techniques including radionuclide scintigraphy and CT angiography. There is no current gold standard and prospective trials are lacking.
Colonoscopy can be a very useful first test to localize the bleeding in stable patients in whom the colon is the suspected source. It has the advantages of being able to visualize the entire colon and any potential bleeding lesions, even after active hemorrhage has ceased. The sensitivity is 74%-100% and is limited by the fact that there is often no active hemorrhage at the time of the examination and stigmata of recent bleeding are seen in only 8%-43% of cases. This limits the utility of preventative treatment in cases with multiple possible sources, such as diverticular bleeding. Depending on the lesion, clips, electrocautery, and/or sclerotherapy may be used. If there is a neoplastic lesion, it can be biopsied or removed. From an efficiency standpoint, colonoscopy makes sense as a first step because it is required at some point in all patients with hematochezia. The disadvantages, including availability of the procedure, need for sedation, and bowel preparation, often preclude its use. It is a generally safe procedure with complication rates of 0%-2%. In order to maximize the utility of colonoscopy, it should be done urgently versus electively. Prospective studies show that lesion identification is more common if colonoscopy is performed urgently versus electively (42% versus 22%), which facilitates the use of directed methods to control and prevent recurrent hemorrhage. In addition, early colonoscopy reduces length of stay and overall cost. Although this has not been shown to improve other outcomes, the power of these trials is limited by small sample size. If the patient is stable and EGD and colonoscopy are both normal, a capsule endoscopy or double balloon enteroscopy may be performed to evaluate for a small bowel source.
If there is ongoing active hemorrhage, a radionuclide scan may be considered. It is used as a screening examination to identify patients in whom angiography may be useful. It utilizes 99mTc-labeled red blood cells. The accuracy increases with increased bleeding rates, but has been reported to detect hemorrhage as low as 0.1 mL/min. Radionuclide imaging is particularly useful in patients with intermittent bleeding owing to the long half-life of the tracer. This allows patients to be scanned on multiple occasions during symptomatic periods. In patients with active bleeding, scans are sensitive and specific for identifying the presence of hemorrhage into the GI tract, however they are unable to precisely localize the source in most circumstances. Once bleeding has been confirmed, angiography is performed for localization and possible treatment. This method has been criticized for causing a delay in therapeutic intervention, although it can prevent angiography in patients who are unlikely to benefit.
CT angiography is a newer technique that is growing in popularity as the technology improves. It does require active bleeding, but can identify the location of bleeding in patients with a rate as low as 0.3 mL/min. Unlike radionuclide scanning, CT angiography can localize bleeding, making for a more accurate and timely intervention by formal angiography. The disadvantages include the additional radiation and contrast exposure for a diagnostic test that cannot be used to treat any identified lesion.
If the radionuclide scan or CT angiogram is positive, it can be followed by selective mesenteric angiography, especially if the source appears to be in the small bowel. Angiography requires ongoing hemorrhage of at least 0.5 mL/min and will likely be of no use if the imaging tests are negative. During angiography, if the site of bleeding is demonstrated, which occurs in 40%-86% of patients, vasopressin or embolization can be used to treat the feeding vessel. Embolism is used if possible because re-bleeding is observed in up to 50% of patients treated with vasopressin alone. Embolization is successful 80%-90% of patients when followed for 30 days. Vascular ectasias can be diagnosed by angiography based on a characteristic pattern of an early filling vein, a vascular tuft, and a delayed emptying vein. These lesions should not be treated if bleeding is not demonstrated as they are quite prevalent and usually asymptomatic. The risks of angiography have decreased with the development of super-selective embolization, however, minor complications occur in 26% and major complications (including death and need for surgery) occur in 17%. One must be especially careful in patients with pre-existing renal insufficiency or diabetes, where the combination of hypovolemia and a large dye load creates a high risk for renal failure. In addition, angiography can rarely provide details about the cause of the bleeding and further work up is required after successful treatment.
In patients who have ongoing hemorrhage and a negative the radionuclide scan, colonoscopy should be considered. This can sometimes be performed successfully in the actively bleeding patient without a bowel preparation because blood acts as a cathartic. Even so, colonoscopy in this situation is difficult. However, a complete examination to the cecum is possible in 55%-70% of patients and there is suggestion that the risk of perforation is increased. Endoscopic therapeutic measures can be applied in up to 40% of patients, with success in half of them. Some gastroenterologists favor performing a bowel preparation under urgent conditions. There are multiple regimens, but usually these consist of a large volume preparation (6-8 L) over a short period of time (4 hours) which increases the chances of electrolyte abnormalities, aspiration, and results in a poor to fair prep in more than half of patients.
The majority of lower GI bleeds will stop spontaneously or be controlled by colonoscopy or angiography. However, 10%-25% of patients will have continued or recurrent bleeding and ongoing shock. Surgery should be considered once the transfusion requirement exceeds six units of blood. However, localization of bleeding is critical to the success of the procedure and the reduction of morbidity and mortality. Rarely, the bleeding site has been localized conclusively and the procedure is limited to segmental colonic resection. The mortality rate is less than 10%. When the source is unclear, intraoperative endoscopy can be performed to try to localize the source. If the patient continues to be unstable and the bleeding is suspected to be in the colon, a total abdominal colectomy may be required. This carries a mortality of 10%-30%. This is a fortunately rare occurrence today with improvements in imaging, endoscopy, and interventional techniques.
Prognosis
Up to 90% of lower GI bleeds will stop spontaneously; however, 25% of patients will experience recurrent bleeding. Mortality has been reported in up to 3.6% of patients.
Geffroy Y, Rodallec MH, Boulay-Coletta I, et al: Multidetector CT angiography in acute gastrointestinal bleeding: why, when, and how. Radiographics 2011 May-Jun;31(3):E35-E46.
Lhewa DY, Strate LL: Pros and cons of colonoscopy in management of acute lower gastrointestinal bleeding. World J Gastroenterol 2012 Mar 21;18(11):1185-1190.
Strate LL, Liu YL, Huang ES, Giovannucci EL, Chan AT: Use of aspirin or nonsteroidal anti-inflammatory drugs increases risk for diverticulitis and diverticular bleeding. Gastroenterology 2011 May;140(5):1427-1433.
VOLVULUS
General Considerations
Volvulus involves rotation of a segment of the intestine on an axis formed by its mesentery (Figure 30–15). This results in a closed-loop obstruction and is therefore a surgical emergency. Luminal obstruction occurs when the bowel rotates 180 degrees. If the bowel rotates 360 degrees, the veins are occluded and arterial flow is interrupted. This leads to ischemia, followed by necrosis and perforation if prompt treatment is not instituted. Sigmoid volvulus can be complicated by the additional development of cecal perforation in patients with a competent ileocecal valve. Physiologically this forms a second closed loop obstruction because the proximal colon is unable to decompress into the small bowel. In this situation, the cecum is at greatest risk of perforation by the law of LaPlace because it has the largest diameter.
Figure 30-15. Volvulus of the sigmoid colon. The twist is counterclockwise in most cases of sigmoid volvulus.
Most cases of volvulus in the United States involve the cecum or sigmoid colon. A minority of patients present with volvulus of the transverse colon or splenic flexure. Volvulus accounts for 5% of all cases of large bowel obstruction in the United States. In pregnant women, volvulus accounts for 25% of intestinal obstructions; most commonly in the third trimester. This may be secondary to the displacement of the colon by the enlarging uterus.
Cecal volvulus often occurs in patients with a hypermobile cecum as a result of incomplete embryologic fixation. The average age of presentation is 53 years. This is in contrast to sigmoid volvulus, which tends to occur in elderly or institutionalized patients who experience high rates of constipation and associated motility disorders. It is thought that a long sigmoid colon with an associated narrow-based mesentery is a risk factor. In parts of Africa and the Middle East, sigmoid volvulus accounts for about 50% of bowel obstructions and tends to effect younger, healthy, male patients. In South America, it is seen in association with megacolon in patients with Chagas disease.
Cecal bascule accounts for 10% of cecal volvulus. It involves anterior-superior movement of the cecum, causing obstruction at the site of the transverse fold in the ascending colon. Patients may describe intermittent bloating, pain, and obstructive symptoms improved by lying down and massaging the abdomen. Mesenteric blood flow is not compromised because there is no twist in the mesentery. However, without treatment these patients are still at risk of gangrene and perforation as a result of the closed loop obstruction.
Clinical Findings
The cecum and terminal ileum are involved in the rotation, so the symptoms generally include those of distal small bowel obstruction. Severe intermittent colicky pain begins in the right abdomen. Pain eventually becomes continuous, and the patient will experience the classic symptoms of obstruction: vomiting, distention, and obstipation. Patients may report a history of similar but milder attacks.
Imaging studies are the key to diagnosis. In the early stages, a plain film of the abdomen may show single fluid level that may be mistaken for gastric dilation. In later stages there may be a hugely dilated ovoid cecum that favors the epigastrium or left-upper quadrant. It is classically described as the “coffee bean” sign. In cecal volvulus, the dilated loop points toward the right-lower abdominal quadrant. If a film is taken later in the course, the x-ray may show classic findings of small bowel obstruction superimposed on the cecal volvulus. The distal colon will be decompressed. The success rate of diagnosis based on plain abdominal films is extremely variable, ranging from 5% to 90%. CT shows a distended cecum, often with a mesenteric swirl sign, indicating the rotation of the mesentery. Ischemia and necrosis can be identified by a lack of bowel wall enhancement.
Sigmoid volvulus presents in a similar fashion to cecal volvulus. Symptoms include intestinal colic, nausea, and obstipation. Distention tends to be more pronounced in sigmoid volvulus. There may be a history of chronic constipation and dysmotility or transient attacks in which spontaneous reduction of the volvulus has occurred. Abdominal x-rays show a markedly distended loop of bowel like a “bent inner tube” that has lost its haustral markings rising up out of the pelvis extending towards the diaphragm. Barium enema reveals a pathognomonic “bird’s beak” deformity with spiral narrowing of the upper end of the lower segment (Figure 30–16). CT should be performed in cases where the diagnosis is unclear as it can demonstrate a dilated sigmoid loop with a mesenteric swirl sign, indicating the mesenteric twist. As with cecal volvulus, the pattern of bowel wall enhancement may help identify patients with ischemia and necrosis of the bowel wall.
Figure 30–16. Volvulus of the sigmoid colon. Barium enema taken with the patient in the supine position. Note the massively dilated sigmoid colon. The distinct vertical crease, which represents juxtaposition of adjacent walls of the dilated loop, points toward the site of torsion. The barium column resembles a “bird’s beak” or “ace of spades” because of the way in which the lumen tapers toward the volvulus.
Differential Diagnosis
Cecal volvulus must be differentiated from colonic pseudoobstruction and from other causes of small bowel and colonic obstruction. Sigmoid volvulus mimics other types of large bowel obstruction. Although x-ray examinations can be helpful, they are often not diagnostic for volvulus, and often a CT is performed which eliminates other causes of the abdominal pain and can provide additional information about the presence of complications.
Treatment
Early diagnosis and treatment are imperative because the involved segment of colon is at risk of gangrene and perforation. The first step in the management of these patients is fluid resuscitation and correction of electrolyte imbalances. Vital signs and urine output should be monitored and a nasogastric tube placed. If there is evidence of ischemia, necrosis, or perforation, antibiotics should be administered as the patient is prepared for emergency surgery.
Many techniques have been described for managing patients with cecal volvulus and cecal bascule, but the recommended treatment is ileocecectomy. This can be done via the laparoscopic or open technique depending on the clinical scenario and surgeon preference. If there is necrotic bowel, the blood supply is ideally controlled prior to releasing the volvulus in an attempt to reduce the systemic release of the potentially infected, acidotic, and hyperkalemic fluid that can cause cardiac arrest. In unstable patients, the bowel can be left in discontinuity and anastomosis performed at a second look laparotomy. However, a primary ileocolic anastomosis is almost always possible. This approach is associated with less than 5% mortality. Cecopexy (suture fixation of the bowel to the parietal peritoneum) and tube cecostomy (placement of a decompressive transabdominal drain) has been used to avoid a resection and anastomosis in the acute setting, however, these techniques have generally been abandoned due to high rates of both recurrence (30%) and complications (50%). Colonoscopic decompression may be attempted if an expert is available, especially in patients who have serious comorbidities that would make operation hazardous. However, this is successful in less than half of patients. This treatment is contraindicated in patients with suspected strangulation, which occurs in about 20% of cases.
In contrast, sigmoid volvulus without strangulation is more commonly treated initially by urgent endoscopy. A flexible sigmoidoscope or colonoscope is advanced to the obstruction. Under direct visualization, the colon is insufflated and the tip of the scope is used to apply gentle pressure. In 70%-90% of patients, decompression is achieved with the immediate release of gas and stool. The mucosa can then be inspected for signs of ischemia. If there is no evidence of ischemia, the patients is ideally scheduled for resection of the affected bowel with primary anastomosis during the same admission. Half of patients managed with decompression alone will have a recurrence within the first year. However, in patients with severe comorbidities, surgery may need to be delayed or may not be an option. Urgent surgery is indicated if strangulation or perforation is suspected or if endoscopic decompression is unsuccessful. In this case, primary anastomosis is not usually possible and a Hartmann’s procedure with washout is performed.
Prognosis
The outcome for patients with volvulus depends on comorbidities, the urgency of the surgery, and the presence of strangulation or perforation. The mortality rate for patients with cecal and sigmoid volvulus is less than 10%, but this increases to 30%-50% if strangulation or perforation has occurred. Patients who undergo semi-elective resection after endoscopic decompression have a mortality rate less than 10%.
Akinkuotu A, Samuel JC, Msiska N, Mvula C, Charles AG: The role of the anatomy of the sigmoid colon in developing sigmoid volvulus: a case-control study. Clin Anat 2011;24:634-637.
Swenson BR, Kwaan MR, Burkart NE, et al: Colonic volvulus: presentation and management in metropolitan Minnesota, United States. Dis Colon Rectum 2012;55:444-449.
Yassaie O, Thompson-Fawcett M, Rossaak J: Management of sigmoid volvulus: is early surgery justifiable? ANZ J Surg 2013 Jan;83(1-2):74-78.
INFLAMMATORY BOWEL DISEASE
Inflammatory bowel disease (IBD) refers to UC, Crohn disease (CD), and indeterminate colitis. The cause of IBD is not known. The disease is likely the result of a combination of genetic, environmental, and host immune response factors.
There is a positive family history of IBD in 15%-40% of patients. Crohn disease seems to have a stronger genetic link than UC. Genome-wide association studies initially identified normal variants of multiple loci associated with the development of IBD; however, these associations are still poorly understood. These genetic associations are heterogeneous and have precluded the development of a useful screening test.
It is postulated that the interplay between the immune system, normal microflora, and colonic epithelium is a factor in the development of IBD, but this is still being investigated. Patients with UC are known to have an increased concentration of normal bacterial flora compared to healthy controls; however, it is not known if this contributes to the disease process. The mucosal immune system has been implicated by the finding that patients with CD have a predominantly Th1 mucosal population, whereas patients with UC have a Th2 predominance. An autoimmune component is suggested by circulating perinuclear antineutrophil cytoplasmic antibody (pANCA) and abnormally high levels of auto-IgG1 antibodies. These antibodies cross react with the epithelium of the colon, biliary tract, skin, eye, and cartilage and have been hypothesized to contribute to extraintestinal manifestations.
Environmental factors are also important. The use of NSAIDs has been associated with flares in patients with CD. Smoking has been shown to be a protective factor for UC. Smokers are less likely to develop the disease, and smoking cessation leads to worsening of disease in smokers with UC. For unclear reasons, this disease is also less common in patients who have undergone appendectomy.
ULCERATIVE COLITIS
General Considerations
UC has a bimodal age distribution, with the first peak between ages 15 and 30 years and a second, smaller peak in the sixth to eighth decades. The annual incidence varies from 1 to 20 per 100,000, and the prevalence is 8-246 per 100,000. UC is more common than CD in adults but less common in children. The disease is found worldwide but is more common in Western countries and the incidence is increasing in Asia. This finding has also contributed to the theory of bacterial flora contributing to the development of the disease.
UC is a diffuse but contiguous mucosal inflammatory disease. Abscesses form in the crypts of Lieberkühn and penetrate the superficial submucosa. In the acute setting, neutrophils predominate whereas in the chronic setting, the infiltrate is largely composed of lymphocytes and plasma cells. There are no granulomas. The overlying mucosa sloughs as the inflammation spreads. Vascular congestion and hemorrhage are prominent, and there is often diffuse thickening of the muscularis mucosa. The normal tissues surrounding the ulcerated areas appear endoscopically protruberant and thus are called pseudopolyps. Except in the most severe forms, the muscular layers are spared. In fulminant disease, the full thickness of the colon wall can be involved, which leads to dilation and ultimately perforation. In patients with long standing or severe disease, the colon becomes shortened and loses its normal haustral markings.
UC classically starts at the rectum and extends proximally without skip lesions. The disease is confined to the rectum (proctitis) or up to the rectosigmoid region (proctosigmoiditis) in at least half of patients. The disease is classified as left-sided colitis if it involves the descending colon, extensive colitis if it extends proximal to the splenic flexure, and pancolitis if the cecum is involved. In patients with pancolitis, a few centimeters of terminal ileum may be involved by proximity in patients with an incompetent ileocecal valve. This is termed backwash ileitis and can make the differentiation of UC from CD challenging. There are no strict diagnostic criteria, but generally a clinical and histologic appearance of UC without evidence of CD is enough to establish a diagnosis and initiate treatment.
Clinical Findings
Patients commonly report frequent, small volume watery stools mixed with blood, pus, and mucus accompanied by tenesmus, rectal urgency, and even fecal incontinence. Many patients will report crampy abdominal pain and variable degrees of fever, vomiting, weight loss, malaise, and dehydration. The symptoms can be episodic with periods of spontaneous improvement or severe and unrelenting. Mild disease may be manifested only by loose or frequent stools, or occasionally constipation. In isolated instances, the only symptoms may be from extraintestinal manifestations such as arthropathy or pyoderma.
If the disease is mild, physical examination may be normal, but in severe disease the abdomen is tender and distended. Severe rectal inflammation may result in considerable tenderness and spasticity of the anus during digital rectal examination. The examining finger may be covered with blood, mucus, or pus. Perianal disease can occur in UC patients as they do in the general population, but signs of anal disease should prompt a workup for CD.
A simple classification of the severity of an attack was devised by Truelove and Witt in 1955. The assessment of disease severity is based on six simple clinical signs including stool frequency, hematochezia, pulse, temperature, hemoglobin, and erythrocyte sedimentation rate (Table 30–8).
Table 30-8. Ulcerative colitis disease severity (based on the Truelove and Witt classification).
There is no single diagnostic test for UC, although in unclear cases, serum antibody tests can help differentiate UC from CD. Serum pANCA are found in 60%-70% of patients with UC but also are found in up to 40% of patients with CD. In patients with IBD for whom the differentiation between UC and CD is unclear, the combination of a positive pANCA and negative anti-saccharomyces cerevisiae antibodies (ASCA) has a specificity of 97%, sensitivity of 48%, and a positive predictive value of 75% for UC. A negative pANCA and positive ASCA has a positive predictive value of 86% for CD. Thus serologic testing in patients with IBD may be helpful when considered in the context of other clinical factors.
During an acute flare, basic laboratory tests are used to assist in determining the severity of disease. Anemia, leukocytosis, and an elevated sedimentation rate or C reactive protein is usually present. Severe disease leads to hypoalbuminemia, dehydration, and electrolyte abnormalities. There is often evidence of steatorrhea. To look for signs of superinfection, the stool should be sent for ova and parasite examination, culture (E. coli 0157:H7 and Campylobacter), and C difficile toxin assay.
In the acute setting, colonoscopy and barium enema should be avoided due to the risk of perforation. If needed for diagnosis, biopsies obtained by proctoscopy should be sufficient. Abdominal x-rays may show dilation of the colon, and can be used to detect free air when perforation is suspected. CT scan has become the most common imaging modality during an acute episode. CT will often show thickened rectum and colon with associated inflammatory changes, however, it does not often lend much to the clinical management of these patients.
Barium enema, which is now infrequently used, shows mucosal irregularity that varies from fine serrations to extensive ulceration with pseudopolyps. As the disease progresses, haustrations are gradually effaced, and the colon narrows and shortens because of muscular rigidity (Figure 30–17). Widening of the space between the sacrum and rectum is due either to periproctitis or to shortening of the bowel. The presence of a stricture should always arouse suspicion of cancer or CD.
Figure 30–17. Ulcerative colitis. Barium enema x-ray of colon. Note shortening of colon, loss of haustral markings (“lead pipe” appearance), and fine serrations at the edges of the bowel wall that represent multiple small ulcers.
In cases where the diagnosis is unclear, a small bowel series or CT enterography may be performed to look for involvement suggestive of CD.
Colonoscopy is an essential part of diagnosis and surveillance. The characteristic mucosal changes include loss of vascular pattern, granularity, friability, hyperemia, and ulceration. Pseudopolyps represent islands of normal mucosa against a background of inflamed, denuded bowel wall. These findings begin in the distal rectum and proceed proximally in a continuous fashion. In more advanced disease, the mucosa is purplish-red, velvety, and extremely friable. Blood mixed with mucus is evident in the lumen. If the mucosa is not grossly diseased, biopsy may be helpful to confirm the diagnosis. In the recovery phase, mucosal hyperemia and edema subside. The healing mucosa is typically dull and granular and has a neovascular pattern of telangiectatic vessels that differs from the normal pink mucosa. Patients with disease distal to the splenic flexure may have a “cecal patch,” an inflammatory lesion at the appendiceal orifice, that can be misidentified as a skip lesion associated with CD. In the acute setting, colonoscopy is important in determining the severity of disease and response to treatment. These patients are at increased risk for CRC. Screening colonoscopy begins 8-10 years after the initial diagnosis of pancolitis and 12 years after left-sided colitis. Surveillance for dysplasia should be done every 1-2 years. At least 30 random biopsies should be taken throughout the colon to detect dysplasia.
Differential Diagnosis
The differential diagnosis of patients presenting with new onset UC is extremely broad and includes all forms of colitis. Cancer and diverticulitis should also be considered. Infectious colitis can mimic UC but can also be superimposed on patients with underlying UC. Salmonellosis and other bacillary dysenteries are diagnosed by repeated stool cultures. Shigellosis may be suspected on the basis of a positive methylene blue stain for fecal leukocytes. Campylobacter jejuni is a common cause of bloody diarrhea; the organisms can be cultured from the stool, and serum antibody titers rise during the illness. Hemorrhagic colitis—a syndrome of bloody diarrhea and abdominal cramps but no fever—is associated with infection by E coli O157:H7. Legionella infections can mimic UC. Gonococcal proctitis is detected by culture of rectal swabs. Herpes simplex virus is the most common cause of nongonococcal proctitis in homosexual men. In patients with suspected amoebiasis, corticosteroids should be held until amebiasis is excluded by microscopic examination of stool, rectal swabs, rectal biopsies, or serologic tests.
Cases of histoplasmosis, tuberculosis, cytomegalovirus disease, schistosomiasis, amyloidosis, or Behçet disease may be very difficult to diagnose. Drug-induced colitis may be suspected based on the patient’s history. NSAIDs can cause mucosal inflammation and even strictures in the large intestine. Collagenous colitis may or may not be related to NSAID use. Watery diarrhea is the main symptom of this syndrome, endoscopy is grossly normal, and biopsies show a thickened band of collagen just beneath the mucosa. Ischemic colitis has a segmental pattern of involvement quite unlike the contiguous distribution of UC. Functional diarrhea can mimic colitis, but organic disease must be excluded before it can be concluded that the diarrhea is functional. Diversion colitis refers to inflammation of a previously normal segment of colon or rectum following construction of a temporary colostomy. Deficiency of mucosal nutrients may be responsible, and inflammation may be treated with topical application of short-chain fatty acids or restoration of intestinal continuity.
The most difficult differential diagnosis is between mucosal UC and Crohn colitis (Table 30–9). None of the features are specific for one disease, and often the differentiation can be made only after all the data have been assembled. Luckily, in the acute phase, the medical treatment is similar, however, the differentiation is important because it can dictate appropriate surgical therapy. About 10% of cases cannot be classified (indeterminate colitis).
Table 30-9. Comparison of various features of ulcerative colitis with those of Crohn colitis.
Complications
Extraintestinal manifestations (EM) occur in approximately 21% of patients with UC. They are more common in women and patients with pancolitis. The pathogenesis is unknown, but it is thought that they may be a result of a systemic autoimmune process. A genetic component is suggested by the fact that they tend to cluster in families. Nearly 80% of patients who develop EM do so after the development of colonic symptoms, but a minority will present with EM prior to symptomatic colonic disease that may lead to a diagnosis of UC. The most common EMs are musculoskeletal (arthralgias, arthritis, ankylosing spondylitis), anterior ocular chamber inflammation (uveitis, iritis, scleritis, and conjunctivitis), skin (erythema nodosum, pyoderma gangrenosum), and primary sclerosing cholangitis (PSC) in order of decreasing frequency. PSC can lead to cirrhosis requiring liver transplant and puts the patient at increased risk for cholangiocarcinoma. For unclear reasons, patients with PSC also develop colorectal cancer at an increased rate. PSC is not improved with treatment of the colonic disease and may develop or progress after curative proctocolectomy. However, arthritis, ocular disease, and skin manifestations are known for paralleling disease activity. Most patients will develop only one EM, but a subset will develop multiple.
Patients with UC also develop symptoms as a result of the disease process in the colon, including iron deficiency anemia and malnutrition. They are at high risk for thrombosis, especially during flares. Patients are also at risk of developing complications from medical treatment using long-term corticosteroids such as diabetes, osteoporosis, cataracts, and adrenal insufficiency.
Gross hematochezia is common during acute flares of UC. In the chronic setting, patients frequently develop a chronic iron deficiency anemia. Ten percent of patients will require blood transfusion for bleeding during a flare. Massive hemorrhage is a potentially life threatening complication that occurs in up to 5% of patients. This is an indication for urgent colectomy and accounts for approximately 10% of all urgent colectomies in patients with UC.
Fulminant colitis occurs in less than 10% of all patients with UC, but in up to 50% of these patients, it develops during their initial presentation. This represents the most severe, acute form of the disease. Patients are systemically ill and develop inflammation extending into the muscular layer of the bowel. Electrolyte disturbances, especially hypokalemia, may contribute to toxicity and should be treated aggressively. Opioids and anticholinergics should be avoided. These patients should be fluid resuscitated and treated with broad spectrum antibiotics. Electrolyte disturbances should be corrected. A nasogastric tube is placed for patients with significant signs of distension. A CT scan can detect perforation or ischemia, as well as other causes of abdominal sepsis. Serial abdominal x-rays can trend colonic distention. However, if there is clinical deterioration or no improvement with maximal medical therapy over the course of 48-72 hours, surgery should be considered. Although barium enema is no longer used to diagnose toxic colon, one can see the classic findings in Figure 30–18. These include a thickened bowel wall and dilation of the lumen greater than 6 cm. Luminal air can be seen outlining irregular nodular pseudopolyps. However, patients do not need to have colonic dilatation to have toxic colitis.
Figure 30–18. Barium enema showing acute colonic dilation in ulcerative colitis. Note dilation of the transverse colon, the multiple irregular densities in the lumen that represent pseudopolyps, and the loss of haustral markings.
Colonic perforation is the most dreaded complication of severe acute UC and occurs in 3% of hospitalized patients. It is responsible for more deaths than any other complication. The risk of perforation is highest during the initial attack of the disease and correlates well with its extent and severity. It may also occur as a complication of endoscopy or barium enema in acutely ill patients. Patients with toxic colitis are especially vulnerable. Perforation is most common in the sigmoid or splenic flexure and may result in a localized abscess or generalized fecal peritonitis. Systemic therapy (corticosteroids and antibiotics) may mask the development of this complication. Therefore, serial abdominal examinations, laboratory tests, and abdominal imaging are important in detecting this complication.
Colorectal cancer risk increases above that of the general population 10 years after the onset of UC, although the rates vary widely between studies. The risk increases with the duration and severity of disease, and is higher in patients with a family history of CRC, extensive colitis, and PSC. Decreased risk in recent reports may be associated with improved medical treatment of colitis. Cancers in UC tend to be multicentric and broadly infiltrating. They are difficult to recognize endoscopically because they arise from small, flat areas of dysplasia located in a background of ulceration and inflammation. They do not follow the typical adenoma-carcinoma sequence seen in sporadic CRC in the general population. Newer techniques, including narrow-band imaging and chromoendoscopy may improve detection.
Colonoscopic surveillance is recommended beginning 8-12 years after the onset of colitis and continues at 1-2 year intervals. Ideally, approximately 48 random biopsies are taken throughout the colon and rectum to screen for dysplasia. Synchronous CRC is found in 20% of patients undergoing proctocolectomy for low-grade dysplasia, 40%-60% of patients with high-grade dysplasia, and 40%-85% of patients with dysplasia-associated lesion or mass (DALM) regardless of the degree of dysplasia. Low-grade dysplasia places the patient at a ninefold increased risk of developing CRC compared to UC patients without dysplasia. In addition, low-grade dysplasia has been reported to progress to carcinoma without progressing to high-grade dyplasia. IBD-associated cancers account for 1%-2% of all CRCs but occur in younger patients and confer a poorer prognosis. High-grade dysplasia and DALM are clear indications for proctocolectomy, and consideration should be given to patients with low-grade dysplasia. Intensive study is ongoing to identify more sensitive screening methods.
Treatment
The goals of medical therapy are to stop an acute flare as rapidly as possible and to maintain remission of mucosal inflammation. Traditionally, medical management has been approached in a “step up” fashion, with treatment depending on the severity of disease (classified as mild, moderate, severe, or fulminant), the extent of colonic involvement, and history of previous response to treatment. However, a new paradigm of “top down” treatment has evolved for patients with severe disease as research has shown improved outcomes with more aggressive treatment. The endpoints of therapy have shifted away from symptomatic improvement to objective mucosal healing and steroid free remission. Mild to moderate disease usually can be treated on an outpatient basis. If the disease flare is refractory or progressive, hospitalization may be required. Patients with severe or fulminant disease may require inpatient treatment for supportive therapy (IV hydration, antibiotics, blood transfusion, and monitoring).
Mild to moderate disease is treated with sulfasalazine or 5-aminosalicylates, such as mesalamine, olsalazine, or balsalazide. Sulfasalazine is cheaper, but associated with more side effects and should not be given to sulfa-allergic patients. These drugs can be administered orally or topically in the form of suppositories or enemas in patients with disease limited to the rectum or sigmoid. Seventy percent of patients will respond to this regimen within 1 month. The remaining 30% are started on prednisone 40-60 mg/d. In patients who do not exhibit objective evidence of response or who remain steroid dependent, azathioprine, 6 mercaptopurine, infliximab, and adalimumab are additional options to induce and maintain remission.
In patients with severe disease, these initial steps are bypassed and treatment with intravenous glucocorticoids is initiated. In addition, biologic agents or immunomodulators are added. Infliximab, an anti-TNF antibody, tacrolimus and cyclosporine have been shown in randomized controlled trials to be effective for treatment of severe flares.
If these regimens are not successful, additional medications or surgery are considered. Multiple new drugs show promise in the treatment of patients with refractory disease. Newer biologic agents, such as certolizumab and natilizumab, as well as Tofacitinib, an oral Janus kinase inhibitor have been shown to be effective in inducing remission in patients with steroid refractory moderate to severe UC. Other treatments, such as stem cells and fecal transplants, are currently under investigation.
Once remission has been obtained, a maintenance regimen is required to prevent relapse in most patients. These regimens should be individualized based on the response to the induction regimen and revised as clinically indicated. For mild disease, mesalamine is commonly used. Patients unable to wean from steroids require intensified treatment. Azathioprine, 6 mercaptopurine, methotrexate, infliximab, adalimumab, or newer immunomodulators may be needed to successfully wean patients off steroids.
In the acute setting, emergency surgery is indicated for colonic perforation. Other complications, such as toxic megacolon, fulminant colitis, or uncontrolled hemorrhage are initially managed medically. However, if there is no improvement with aggressive medical therapy, surgery is warranted. There are no firm guidelines for how long patients should be treated medically prior to considering surgery. These patients are monitored closely for 48-72 hours. If there is clinical deterioration or no improvement, surgery is indicated.
Another group of patients in whom surgery is considered are those with intractable disease despite maximal medical therapy or those who cannot wean off steroids due to worsening symptoms. In children this may present with growth retardation. Adults may become physically debilitated, psychosocially limited, and experience poor quality of life. There may be medication intolerance, especially in those patients who are steroid dependent. Surgery is also considered for patients with severe extraintestinal manifestations that have developed in parallel with the UC flares such as peripheral arthritis, pyoderma gangrenosum, and ocular manifestations. These may respond to colectomy.
Patients who have biopsy-proven carcinoma are offered proctocolectomy as opposed to standard oncologic resection because this treats both the UC and the cancer. Further, colitis-related CRC tends to be widely infiltrative, multicentric, and difficult to visualize making standard oncologic resection dangerous. Patients with dysplasia or dysplasia-associated lesion or mass are also candidates for surgery as the risk for a synchronous or metachronous malignancy is high as discussed previously.
In the elective setting there are two surgical options. Proctocolectomy with ileal pouch-anal anastomosis (IPAA) is the operation of choice in most patients because it provides intestinal continuity (Figure 30–19). However, total proctocolectomy with a permanent end ileostomy is indicated in a subset of patients. Factors include preoperative sphincter function, presence of carcinoma low rectal cancer, and the patient’s age, general health, and preferences. IPAA is contraindicated in patients with poor baseline sphincter tone or in whom a diagnosis of CD cannot be excluded. Both procedures are now increasingly performed laparoscopically with equivalent functional results and improved short-term outcomes.
Figure 30–19. View of the pelvis after colectomy and ileoanal anastomosis in a male. The J-pouch, shown here, is one of several types of reservoirs and is most commonly utilized. The pouch is anastomosed to the anal canal just above the dentate line.
A permanent end ileostomy may be desired by patients who have concerns about the postoperative complications or anticipate difficulty managing the changes in bowel function associated with the ileoanal pouch. Patients frequently experience greater than 10 bowel movements per day during the first 3 months. This eventually decreases to an average of 5-7 bowel movements per day. Twenty percent of patients experience nocturnal seepage or incontinence 1 year after surgery. The most common complications after surgery include small bowel obstruction, infertility, sexual dysfunction, and pelvic sepsis as a result of anastomotic or pouch leaks. Pelvic sepsis occurs in 25% of patients and is the most common cause of pouch failure. Pouchitis affects 40% of patients in the first 10 years after surgery. This is an idiopathic inflammation of the ileoanal pouch that causes abdominal pain, increased bowel movements, and bleeding. It is treated with antibiotics.
Proctocolectomy with IPAA can be performed as a one-, two-, or three-stage procedure. In the elective setting, a two stage procedure is most common, involving proctocolectomy with IPAA and diverting loop ileostomy at the first surgery followed by ileostomy reversal as a second surgery. A single stage operation (without diverting loop ileostomy) is performed only in the most ideal candidates. This approach eliminates the ileostomy-associated complications and avoids a second surgery at the increased risk of the potentially significant consequences of pelvic sepsis from an undiverted anastomotic leak. The three stage procedure is reserved for ill patients who would not tolerate the IPAA during the first surgery secondary to malnutrition or severe active disease. It is also useful in patients with indeterminate colitis in whom confirmation of UC may be made after pathologic evaluation of the surgical specimen allowing the safe formation of the IPAA. The first procedure is a subtotal colectomy with end ileostomy, followed by completion proctectomy, and IPAA. At the time of this procedure, an ileostomy may be avoided in selected patients, otherwise the ileostomy is reversed at a third operation. In the interval between subtotal colectomy and proctectomy, the residual disease in the rectal remnant improves with fecal diversion and if symptoms persist, it can be treated locally with suppositories or enemas.
Proctocolectomy involves mobilizing and resecting the entire colon and rectum. If IPAA is planned, the anal sphincter complex is left in place. The ileum is made into a reservoir most commonly with a “J” configuration (although multiple configurations have been described) and an anastomosis is created just above the dentate line (Figure 30–19). A diverting loop ileostomy is used to protect the anastomosis if there is any intraoperative concern about the anastomosis or if the patient has risk factors for impaired healing such as steroid exposure, anemia, diabetes, or malnutrition. Most of these patients will have been treated with immunosuppressants or immunomodulators in the preoperative period. Although these medications theoretically impact healing, there is no clear evidence to suggest that they increase surgical complications in the setting of diversion.
The continent ileostomy, which was first reported by Kock in 1969 is plagued by complications requiring reoperation in 50% of patients. It has largely been replaced with the IPAA and is mainly mentioned for historical purposes.
The mortality rate of UC has dropped sharply in the past two decades. First attacks are seldom fatal when treated by specialists. In one large series, emergency colectomy was required in 25% of patients with severe first attacks; 60% responded rapidly to medical therapy; and 15% improved slowly on medications alone. Overall, the colitis-related mortality rate during the year after onset is about 1%. Emergency colectomy has a mortality rate of 6%; most of these deaths occur in patients with preoperative perforation, a complication that has a fatal outcome in 40% of cases.
Compared to pancolitis, the long-term prognosis of ulcerative proctitis is excellent; only 10% of patients will develop colonic disease by 10 years, and the mortality rate is very low. In patients with pancolitis, the likelihood of operation during the first year is about 25% and the mortality rate is 5% over 10 years. Colorectal cancer in UC is more often diagnosed at an advanced stage than is sporadic cancer, but the stage-for-stage prognosis is the same. Screening with colonoscopy and biopsies seems to have reduced the cancer mortality rate, but there are still many patients who escape detection until the malignancy has progressed to an advanced stage. The operative mortality rate is less than 1% for elective colectomy.
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CROHN COLITIS
General Considerations
Approximately 45% of patients with CD have diffuse involvement of the GI tract; 30% have disease limited to the small bowel, 20% have disease limited to the colon, and another 5% have isolated anorectal involvement. Symptoms, including diarrhea, abdominal pain, constitutional effects, and extraintestinal manifestations are approximately the same in colonic and enteric disease. Fistulas, abscesses, and intestinal obstruction are more often complications of small bowel disease. Anorectal complications such as anal fistula, fissure, abscess, rectal stricture, as well as hemorrhage occur more commonly in patients with disease affecting the large bowel.
Clinical Findings
Patients present with abdominal pain, diarrhea, and systemic signs such as low-grade fevers, weight loss, and malaise. Symptoms are generally dictated by the distribution of disease, but patients with Crohn colitis may report urgency or mucous, blood, or pus per rectum. Patients with perianal disease may present with perianal pain or discharge. If the inflammatory process has caused structuring, partial obstructive symptoms may be present.
Radiographic features include sparing of the rectum, right colonic and ileal involvement, skip areas, transverse fissures, longitudinal ulcers, strictures, and fistulas. Typical anal lesions of CD include fissures, abscesses or fistulas. Large external skin tags are also common. The differential diagnosis is broad and includes all forms of colitis including UC, infectious and ischemic. Features differentiating CD from UC are summarized in Table 30–9.
Colonoscopy
Colonoscopy is indicated for diagnosis, evaluation for severity of disease, determining response to treatment, and screening for colorectal cancer. Colonoscopy with biopsy is a mainstay in diagnosis. Patients with Crohn colitis have rectal sparing about 50% of the time. Skip lesions are common, with irregular ulcerations separated by edematous or even normal-appearing mucosa. Patients with pancolitis appear to have similar risk profile for cancer as their UC counterparts. The risk of colorectal cancer in Crohn colitis patients is 4 to 20 times that of the general population. The 25-year risk of dysplasia in patients with Crohn colitis is 12%-25%. Data to support surveillance and management strategies for patients with Crohn colitis are limited and often extrapolated from UC patients. Routine annual colonoscopy with random biopsies is recommended beginning 8 years after the diagnosis. Surveillence should include high risk areas, such as segments of intestine excluded from the fecal stream, strictures, and fistulas with focused biopsies performed as needed.
Treatment
Steroids are effective for acute attacks in up to 70% of patients, but they are not used for maintenance therapy because of the associated side effects and complications. Up to 45% of patients who initially improve with steroids will relapse upon tapering or withdrawal. Oral 5-aminosalicylates (sulfasalazine, 4 g/d; or mesalamine, 2-5 g/d) are effective treatment for Crohn colitis. Topical 5-aminosalicylates are beneficial for disease of the rectum and sigmoid and are often used to wean patients off steroids. Anal abscesses and fistulas require surgical drainage and seton placement to treat local sepsis, but healing is improved with biologic agents.
Immunosuppressants (azathioprine, mercaptopurine, methotrexate) are steroid-sparing drugs that seem to control Crohn colitis well enough that surgery is delayed or avoided. Biologic agents including infliximab and other anti-TNF therapies are effective for inflammatory CD and also specifically indicated for fistulizing or refractory disease. Patients who respond to infliximab induction should receive maintenance therapy. Adalimumab is an effective therapy for patients who are refractory or intolerant to infliximab. Newer human monoclonal antibodies, such as the anti-TNF natalizumab and anti-interleukin ustekinumab have shown promising results in preliminary clinical trials and are now being used more frequently for patients who initially responded to other agents.
Failure of medical therapy, neoplasia, and complications of CD are indications for surgery. Patients whose symptoms do not respond to medical treatment, are unable to achieve remission, have intractable weight loss, or have unmanageable side effects should be considered. The choice of operation depends on the severity and distribution of disease, but the general principle is bowel preservation, with resection of only diseased, actively symptomatic areas. In contrast to UC, CD is not cured surgically, and procedures are performed with palliation in mind. However, patients who have distal colon and rectal disease or multiple segments of disease often do better with a proctocolectomy. Disease tends to recur, especially at areas of intestinal anastomosis and short bowel syndrome is a major concern. Cigarette smoking is an independent risk factor for recurrence of CD after resection.
Strictures are more common in patients with longstanding disease. The use of CT or MR enterography is useful to localize the lesion. If the lesion is symptomatic and unresponsive to medical therapy, resection is indicated. If the lesion is asymptomatic, malignancy should be ruled out with biopsies or brushings. Lesions not amenable to surveillance should be considered for resection, as 7% are malignant.
Intra-abdominal abscesses may be managed with percutaneous drainage and antibiotics. Those who do not respond to conservative management may need an operation. Patients with CD are at risk of developing enterocutaneous and enteroenteric fistulas spontaneously or after surgical intervention, and if diagnosed, nutritional optimization and control of sepsis are of utmost importance.
Five percent of patients will develop severe or fulminant colitis. These patients should be treated in a similar fashion as patients with UC including bowel rest, intravenous fluids, broad spectrum antibiotics, and aggressive CD therapy. They should be closely monitored with serial abdominal examinations, laboratory tests, and imaging as indicated. Patients with CD more commonly respond to medical management than patients with UC. When patients require surgery, total abdominal colectomy with end ileostomy is the most common operation performed in the acute setting, although if by operative inspection the disease is limited to a specific part of the large bowel, this can be resected with creation of a colostomy and Hartmann’s pouch or mucous fistula. Isolated perforation without toxic megacolon is preferentially treated with segmental resection, as simple closure is associated with a higher mortality rate. Diversion is commonly performed in colonic perforations and occasionally for perforation of small bowel depending on the clinical status of the patient and the intraoperative findings.
Perianal complications include perianal abscess, fistula, ulcer, and fissure. These processes are treated using the same methods as are used in non-IBD patients, although these problems tend to be more complicated and chronic, requiring dedicated surgical follow-up. The key elements to treatment are elimination of sepsis and protection of the anal sphincter.
Dysplasia or cancer of the colon requires surgical treatment. Depending on the location and extent of disease, proctocolectomy or segmental resection is performed for high-grade dysplasia, dysplasia-associated lesions or mass lesions. Twenty percent of patients with high grade dysplasia are found to have carcinoma in the surgical specimen, and half of patients known to have cancer preoperatively are found to have remote dysplasia upon pathologic review. For this reason, total proctocolectomy with end ileostomy should be considered in patients found to have cancer or high grade dysplasia on surveillance colonoscopy.
Prognosis
Surgical procedures—like medical therapy—should be regarded as palliative, not curative, in patients with CD. Although recurrence rates are high and chronic disease is common, a productive life is usually possible with the aid of combined medical and surgical management. The mortality rate is about 15% over 30 years.
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PSEUDOMEMBRANOUS COLITIS
Pseudomembranous colitis is caused by C difficile. C. difficile colitis was first reported in 1978 but the incidence and severity of infection is increasing with time. Of particular concern is the increasing virulence, with reports of antibiotic resistance and mutant strains with uncontrolled toxin production. Infection causes a range of illness from mild diarrhea to fulminant, life threatening colitis and is particularly dangerous in frail or immunocompromised patients.
Microbiology
Clostridium difficile is a spore-forming organism that is ubiquitous in the environment. It is a commensal gut organism that exists in 5%-15% of the general population and up to 57% of patients in long-term care facilities. The spores are dormant and extremely resistant to disinfectants and extreme environments. Spread by health care practitioners is reduced significantly by the use of standard contact precautions including disposable gowns and gloves and hand washing with water and soap. Alcohol-based hand sanitizers are not effective. Once ingested, the spore is reactivated after contact with bile salts in the small intestine.
The bacterium exists in both toxin-producing and nonproducing forms. Only the toxin-producing bacterium is capable of causing colitis. Toxins A, B, and binary toxin induce apoptosis and provoke inflammation. The epidemic-associated 027 strain is thought to have a mutation causing increased production of toxins A and B, as well as enhanced sporulation making it particularly virulent and transmittable. These toxins as well as a variety of nontoxin virulence factors cause pseudomembranous colitis.
Although C. difficile is commensal and the spores are easily transmitted, the presence of normal colonic flora is usually enough to prevent infection. Symptoms generally only occur when the normal flora is disrupted. Therefore, pseudomembranous colitis most often occurs in patients taking antibiotics. Clindamycin is historically the most common cause, but all antibiotics that alter the gut flora have the potential to cause infection. Pseudomembranous colitis may develop as early as 2 days after exposure to antibiotics but has been reported many weeks after they are discontinued. Other risk factors include surgery of the gastrointestinal tract, immunosuppression, and use of proton pump inhibitors and H2 blockers.
Symptoms and Signs
The most common symptom is diarrhea, which is usually watery, occasionally bloody, and has a characteristic foul odor. Other symptoms include colicky abdominal pain, vomiting, and fever. C. difficileinfection may also cause a paralytic ileus and therefore, can present without diarrhea. Depending on the severity, patients may present with abdominal distention, tenderness, dehydration, and sepsis. The stool is usually positive for leukocytes. Radiographic studies may reveal colonic wall thickening due to submucosal edema. On abdominal films, this may appear as a “target sign.” CT scanning is reserved for patients with complicated disease. It may show colonic wall thickening, ascites, colonic dilation, or perforation.
Changes in the colonic mucosa depend on the severity of the infection. Endoscopy performed for mild to moderate cases will show erythema and edema of the mucosa, with occasional hemorrhage. In severe cases, findings include elevated whitish-green or yellow plaques like “pseudomembranes” overlying inflamed mucosa. The pseudomembrane is made up of leukocytes, necrotic epithelial cells, and fibrin. The rectum is spared in about one-fourth of cases.
Diagnosis
The gold standard for diagnosis of C. difficile colitis was a cytotoxin neutralization assay. This has largely been abandoned owing to its technical difficulty and length of time required to obtain a result (24-48 hours). Instead, the 2013 American College of Gastroenterology (ACG) guidelines recommends using PCR amplification of the genes for toxins A and B from a stool sample. This test has high sensitivity (87%) and specificity (97%) and is cost effective. It can be used as a sole diagnostic test or as part of a two-step approach using a glutamine dehydrogenase (GDH) screening assay, and if positive, following with the PCR confirmatory test. The guidelines recommend against the popular enzyme-linked immunoassay for toxins A and B owing to a cited lack of sensitivity and specificity (75%-95% and 83%-98% respectively); however, the test is still widely used for its ease of performance, low cost, and some studies show similar effectiveness. Stool culture is limited to use in epidemiologic studies. Finally, retesting stool for cure is not recommended because there is a high rate of positive tests after clinical cure, which may lead to prolonged and unnecessary treatment.
Treatment
After discontinuing the inciting antibiotic agent, which is the first step in treatment for any patient, management is determined by severity of disease. In the United States, vancomycin and metronidazole are the drugs of choice. ACG guidelines recommend treatment of mild to moderate infections with Metronidazole 500 mg three times daily for 10 days. If there is no clinical improvement by day 5, vancomycin is started at a dose of 125 mg orally four times daily for 10 days. Both antibiotics have similar efficacy in patients with mild to moderate disease, but metronidazole is cheaper ($2/d vs. $71-$143/d). A third agent, fidaxomicin, was FDA approved for treatment in 2011 after phase III trials showed non-inferiority for clinical cure and decreased rates of relapse compared to vancomycin in mild-moderate disease. However, this drug is more expensive than vancomyin ($280/d) and post-marketing clinical trials are still underway. There is some evidence that teicoplanin, a bacteriocidal antibiotic, is more effective than vancomycin. However, its use is limited as it is extremely expensive and not available in the United States.
Severe infections (serum albumin < 3 with either a WBC > 15,000 or abdominal tenderness) are treated initially with vancomycin, 125 mg orally four times daily for 10 days, which has been shown to be more effective in patients with severe disease. Patients with complicated disease (admission to ICU, hypotension, fever > 38.5, abdominal distention, altered mental status, WBC > 35,000 or < 2000, lactate > 2.2, or organ failure) are treated with combination therapy consisting of vancomycin 500 mg orally four times daily, vancomycin enemas, and metronidazole 500 mg IV every 8 hours.
Recurrent disease is less well studied, however, ACG guidelines recommend standard treatment if symptoms are mild to moderate. If the patient has more severe illness, treatment should be stepped up as indicated. Oral vancomycin should be administered as a first line treatment and there is some evidence to suggest that pulsed vancomycin can be helpful in patients with multiple recurrences. There is mounting evidence, including a small randomized clinical trial, showing superior clinical efficacy in patients treated with vancomycin plus fecal transplant as opposed to vancomycin alone.
Although most patients will respond to initial medical management, a subset will develop complicated or “fulminant” colitis. Risk factors include patients with IBD, recent gastrointestinal surgery, and WBC greater than 16,000. These patients are critically ill and have a mortality rate of 35%-80%. An abdominal CT scan is indicated to look for complications of C. difficile colitis, such as toxic megacolon and perforation, and exclude other intra-abdominal pathology. Surgical evaluation is recommended for patients with shock (altered mental status, organ dysfunction, lactic acidosis) peritonitis, significant leukocytosis, or failure to improve on medical therapy for 5 days. Although there have been no randomized controls, timely surgery for these patients provides a substantial decrease in mortality. Given the diffuse involvement of the colon and the severity of the illness, a subtotal colectomy with end ileostomy is recommended. Residual rectal disease may be treated with vancomycin enemas if needed. Intestinal continuity is restored at a later operation.
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ISCHEMIC COLITIS
Ischemic colitis refers to colonic inflammation caused by inadequate perfusion. It is more common in elderly patients and has a mortality of 13%. It occurs as a result of an occlusive or non-occlusive insult. Examples of occlusive ischemic colitis include embolism, thrombosis (arterial or venous), atherosclerosis, trauma, and postsurgical causes such as patients with loss of inferior mesenteric blood supply after aortic aneurysm repair and those with inadequate perfusion to colonic anastomoses. Nonocclusive injury may occur as a result of shock, vasopressors, vasospasm, mechanical obstruction of the lumen, or systemic vasculitides.
An important clinical distinction that must be made when evaluating patients is assessing the colon for gangrenous and non-gangrenous ischemic colitis. Patients with gangrenous forms have transmural, nonreversible injury that is rapidly fatal without surgery. The non-gangrenous type is divided into transient reversible and chronic forms. The chronic form involves the muscularis propria and is prone to stricture development. Transient reversible ischemia involves the submucosa and heals without sequelae. Most cases of ischemic colitis are idiopathic and attributed to a nonocclusive state.
Patients with ischemic colitis present with diarrhea (90%), hematochezia (65%), and abdominal pain (58%). A history of atrial fibrillation, thrombophilia, atherosclerotic arterial disease, recent trauma or surgery, or systemic vasculitis should be sought. Recent severe systemic illness with shock is a common suspected cause. There may be localized or diffuse peritonitis. Blood tests may reveal leukocytosis, hyperamylasemia, and acidosis, as well as electrolyte derangements. The most common location is the sigmoid colon (40%) followed by the transverse colon (17%), splenic flexure (11%), ascending colon (12%), and the rectum (6%).
The most useful diagnostic tests are endoscopy and abdominal CT. Colonoscopy is the diagnostic modality of choice (although contraindicated in critically ill patients with peritonitis) as it allows diagnostic confirmation, determination of severity, and can rule out other types of colitis. The mucosa of the involved segment is edematous, hemorrhagic, friable, and sometimes ulcerated. A grayish membrane may be present, resembling pseudomembranous colitis, but the presence of hyalinized, hemorrhagic lamina on biopsy will differentiate colonic ischemia from C difficile colitis. Serial endoscopy can be used to identify patients with progression of mucosal lesions who require surgery. Abdominal CT with contrast shows a thickened colonic wall, decreased wall enhancement, pneumatosis, and occasionally a disruption in the arterial circulation. It is also useful to exclude other conditions.
Initial treatment for patients without gangrene suspected to have reversible ischemic colitis consists of intravenous fluids, bowel rest, broad spectrum antibiotics, and observation with serial abdominal examinations. Approximately 20% of patients will have irreversible disease, whether gangrenous from the beginning, becoming more severe over several days, or just failing to resolve after treatment. These patients need surgery. The extent of the resection is based on the amount of necrotic or severely diseased colon. Most commonly a segmental resection is required, although a subtotal or total colectomy is performed in 20% of patients. Depending on the etiology of the ischemia and the appearance of the remaining bowel, a second-look laparotomy may be planned 12-24 hours later. Primary anastomosis is rarely performed and intestinal continuity is restored during a subsequent operation.
O’Neill S, Yalamarthi S: Systematic review of the management of ischaemic colitis. Colorectal Dis 2012 Nov;14(11):e751-e763.
NEUTROPENIC COLITIS
Neutropenic colitis, also referred to as neutropenic enterocolitis, necrotizing enteropathy, ileocecal syndrome, and typhlitis, is a syndrome of colonic necrosis occurring in neutropenic patients. The cause is poorly understood, but likely involves mucosal injury and unimpeded bacterial translocation as a result of profound immunosuppression. Neutropenic colitis should be on the differential diagnosis for any immunosuppressed patient with abdominal pain; however, it is most common in neutropenic patients undergoing chemotherapy with cytotoxic agents such as the vinca alkaloids and doxorubicin. There are reports in patients with acquired immunodeficiency syndrome (AIDS), aplastic anemia, cyclic neutropenia, and those being treated with a variety of immunosuppressants for other conditions.
The clinical presentation ranges from mild to life-threatening and overall mortality is 30%-50%. Symptoms include fever, nausea, abdominal pain, distention, and watery or bloody diarrhea. These patients often present late and with deceptively benign findings on physical examination owing to the inability to mount a normal inflammatory response. The cecum and right colon are most often affected; however, any part of the small or large bowel, including the appendix, can be involved. Patients are commonly bacteremic and/or fungemic. Causative organisms include gram-negative rods, gram positive cocci, anaerobes, and candida.
Diagnosis is confirmed using abdominal CT scan, which demonstrates bowel wall thickening, distention, and may show pneumatosis or perforation. Initial management consists of bowel rest, intravenous fluids, and broad spectrum antibiotics. Antifungals are started if there is evidence of fungemia or persistent fevers on antibiotics. Resolution of neutropenia is an important prognostic factor, therefore, discontinuation of immunosuppressants, chemotherapeutics, and administration of granulocyte colony stimulating factor (G-CSF) should be considered. Surgery is recommended for patients with perforation, persistent bleeding, or who do not improve with medical management. Most patients undergo segmental resection with proximal diversion.
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INTESTINAL STOMAS: ILEOSTOMY AND COLOSTOMY
Creating an intestinal stoma involves exteriorizing a part of the bowel wall onto the surface of the abdomen. This section will focus on the two most common stomas created in colon and rectal surgery–those made from the ileum (ileostomy) and colon (colostomy).
Indications
Stomas are generally created to protect a distal anastomosis temporarily or as a permanent route for enteric contents when the colon and/or rectum has been resected. There are two configurations for a stoma. The end ileostomy or colostomy is created by fixing the end of the ileum or colon to the abdominal wall. The loop ileostomy or colostomy involves bringing a segment of ileum or colon to the abdominal wall and opening the side of the bowel leaving both a proximal and distal opening. In general, very little, if any, stool passes through the distal limb if the stoma is well constructed. This allows retrograde decompression of the distal bowel and has the benefit of being easier to reverse as both limbs are at the abdominal wall.
In the elective setting, loop ileostomies are commonly used to protect ileoanal anastomoses and low pelvic colorectal or colo-anal anastomoses. These ileostomies are temporary, and divert most of the fecal stream away from the anastomosis. End ileostomies (Figure 30–20) are used in the elective setting for patients who require proctocolectomy and do not desire or are not candidates for IPAA reconstruction. They are also commonly used in patients who require emergency subtotal colectomies and will not tolerate an anastomosis due to severe illness.
Figure 30–20. Ileostomy after colectomy. A: A midline incision for colectomy is indicated by the dotted line and the site of the ileostomy by the black dot. B: The ileum has been brought through the abdominal wall. C and D: The ileostomy stoma has been everted and its margins sutured to the edges of the wound.
The Kock pouch, or continent ileostomy, involved an ileal reservoir and construction of a valve at skin level to allow the patient to catheterize the stoma multiple times per day. This allowed patients not to wear a stoma appliance and to control the timing of stool output. However, this procedure is associated with a high rate of complications and failure. It has largely been replaced with the IPAA.
Colostomies (Figure 30–21) are used in patients with low rectal cancers requiring APR or LAR who are not candidates for a low anastomosis. In addition, they are useful in patients who require diversion for chronic fistula disease or in the emergency setting for patients with a large bowel obstruction, perforation, or trauma where an anastomosis is unlikely to heal or the patient is too ill to tolerate it. Loop colostomies are infrequently used as they are associated with a higher complication rate, particularly prolapse, although they are easier to reverse.
Figure 30–21. End colostomy. The margins of the stoma are fixed to the skin with sutures.
Technical Aspects
When possible, patients should meet with their enterostomal therapist or surgeon prior to their operation for education, counseling, and stoma marking. Preoperative stoma marking has been shown to reduce complications and improve postoperative quality of life. Ileostomies are typically placed in the right-lower quadrant and colostomies in the left-lower quadrant. The placement should avoid wrinkles, folds, scars, and hernias on the abdominal wall. It should be at least 2 inches from the surgical incision and have a clear area extending 2-3 inches around it. It must be visible to the patient. Ideally, it is situated below the patient’s belt line in the lateral rectus. The patient should be evaluated in the sitting, standing, and lying positions with and without clothing. The mark is made with active patient participation and it is ideal to provide a stoma appliance for the patient to wear over the mark for several days prior to the operation to ensure it is the optimal position.
There are several key steps during the operation that when followed, can reduce the chance of complications. The first step is to ensure adequate mobilization of the bowel so that the stoma will lie without any tension and will not retract into the abdominal wall. The second step is to pay close attention to the blood supply and preserve the mesentery and associated vessels during mobilization to avoid ischemic injury and subsequent stenosis. The third step is to create a defect in the rectus that is as small as possible that will still allow the stoma to pass without ischemia in order to prevent herniation. Lastly, when maturing the stoma, the aim should be to create 2-3 cm of bowel protrusion to ensure good appliance adhesion and improve skin protection.
Management
Having a stoma changes a patient’s life in many ways and is associated with an overall complication rate of 20%-70%. For this reason, these patients, especially those with newly created stomas and those experiencing complications require dedicated management.
An ileostomy has a near-continuous stream of liquid and semi-solid material whereas a colostomy tends to produce more formed stool. Both generally require an appliance to be worn at all times. Some patients choose to irrigate their colostomies to avoid stool output during the day. The sound and timing of flatus cannot be controlled by patients.
After ileostomy creation, there are significant changes in water and electrolyte absorption owing to the loss of the colon (Table 30–1). The small bowel adapts over the first 2 months after surgery. Output increases over the first week up to 1-2 L per day, stabilizes, and over the next 2 months steadily decreases to a steady state of 500-800 mL per day. Output can be higher in patients with diseased small bowel or more proximal stomas. Sodium excretion averages 60 mEq per day, which is two to three times that of patients with intact colons. These patients are at risk for developing salt depletion and dehydration, especially during times of illness or exposure to hot weather. They must take care to stay hydrated and to consume enough salt and potassium in their diets to make up for this. Generally, switching to a bland, constipating diet high in breads, cereals, dairy, peanut butter, bananas, and rice will help decrease high output and reduce fluid and electrolyte losses. Fiber supplements and antimotility agents such as loperamide or diphenoxylate can be added as needed.
Patients with colostomies are less prone to metabolic disturbances, especially with the more common distal (sigmoid) colostomy configuration. Generally, they will continue to have formed bowel movements similar to their previous bowel habits. Fecal impaction will require irrigation in some patients. Transverse colostomies produce semi-liquid effluent and tend to be difficult to manage. They should be avoided for this reason.
Complications
Stomas are associated with a complication rate of 20%-70%. Ileostomies and colostomies are associated with similar complication rates. There is an association of loop colostomy and transverse colostomy with higher complication rates; however, this has never been studied in a randomized fashion and the data are conflicting. The complications seen in ileostomies are different than those seen with colostomies. Ileostomies are more likely to cause high output and dermatitis, whereas colostomies are more likely to develop hernia and odor.
A parastomal hernia refers to herniation of intra-abdominal contents through the defect in the fascia created for the stoma. In the chronic setting, parastomal hernias cause pain, difficulty with stoma appliance fitting, obstruction, and changes in stooling patterns. In the acute setting, there is a risk of incarceration and strangulation. Herniation is more common in patients with end-stomas as opposed to loop-stomas and more common in colostomies than ileostomies. The risk is minimized by creating a fascial defect that is just large enough to accommodate the bowel without ischemia. Some studies have shown a decreased risk of hernias in stomas placed through the rectus muscle, with fascial fixation, and when the preoperative marking is performed by an enterostomal therapist. Other risk factors for hernia development include obesity, COPD, poor nutritional status, and immunosuppression. There is also an increased risk of hernia with time. Conservative management is successful in 70% of patients and includes abdominal binders and restriction on heavy lifting. Flexible ostomy appliances may decrease leaking. Up to 30% of patients will require surgical revision either for failure of conservative management or for presentation with incarceration or strangulation. Surgical treatments vary depending on individual patient factors. Options include stoma relocation and mesh repair. Mesh repairs can be local or intraperitoneal, open or laparoscopic. Intraperitoneal synthetic mesh repairs have the lowest recurrent rates, although this approach involves more surgical risk as well as the risk of mesh erosion or infection. Some small studies have shown prophylactic mesh placement to reduce the incidence of parastomal hernia without increasing surgical morbidity, although it is unclear if this approach is cost effective or if the effect is long term.
Stoma prolapse occurs in up to 42% of patients and is associated with similar risk factors as parastomal hernia. In fact, these two complications frequently coexist. It is more common in colostomies and specifically the distal limb of loop colostomies owing to defunctionalization and atrophy from non-use. Symptoms include pain, poor fitting of the stoma appliance, and may progress to obstruction, incarceration, or strangulation. Indications for repair include intractable symptoms or an acute presentation with impending bowel compromise. Incarcerated prolapsed stomas can often be reduced using topical sugar, which draws edema fluid out of the bowel wall allowing reduction. Surgical treatment depends on individual patient factors and options include resection, revision, and relocation.
High volume stoma output is defined as effluent greater than 2 L or any volume leading to dehydration. It is the most common cause of hospital readmission in patients with ileostomies. Patients with intrinsic small bowel disease (such as CD) or proximal stomas are at particularly high risk. Symptoms include dark urine, fatigue, irritability, muscle cramps, and headache. Patients develop dehydration and hyponatremia, which can result in secondary hyperaldosteronism and urinary potassium and magnesium wasting. Treatment is through rehydration, correction of electrolyte abnormalities, and antimotility medications. In the acute setting, intravenous fluids and electrolyte repletion are used, with some patients requiring total parenteral nutrition for a period of time. For marginally dehydrated patients, an isotonic glucose and sodium oral rehydration solution is effective. Long term, patients can use elemental, high carbohydrate, low fat diets to slow output. Helpful foods include breads, cereals, peanut butter, bananas, and rice. Medications such as loperamide, diphenoxylate, and tincture of opium can be used as adjunctive therapy. In refractory cases, the addition of H2 antagonists or proton pump inhibitors as well as octreotide have been shown to be effective.
Skin complications are common in patients with ileostomies. It is associated with parastomal henrniation, retraction, and prolapse, which contribute to poor appliance adherence, and high volume output, which increases leaking. Obese and diabetic patients are more commonly affected. It is most commonly a chemical dermatitis but can result from underlying Candida infection or even pyoderma gangrenosum in patients with IBD. Skin irritation can be avoided with dedicated skin care, reducing the number of appliance changes as much as possible (with a goal of one to two times per week), and surgical correction of contributing factors such as hernia or prolapse. Candida infections are treated with topical antifungals. Pyoderma gangrenosum is a notoriously difficult condition to treat, but may be responsive to local wound care, tacrolimus ointment, and intralesional steroid injections. Occasionally systemic tacrolimus or steroids are required.
Stoma retraction affects 1%-6% of patients with colostomies and 3%-17% of patients with ileostomies. This generally occurs in the immediate postoperative period as a result of tension on the bowel or poor wound healing and occurs more often in obese patients. It causes poor fitting of the stoma appliance and may lead to severe skin irritation. Some patients will be adequately treated with convex appliances, however, many will require surgery. Local revision is a reasonable first step. However, because this does not address tension on the bowel, some patients will progress to require laparoscopic or open revision.
Stenosis is uncommon, affecting 1%-10% of patients. Patients present with obstructive symptoms, or intermittent periods of no stoma output and crampy abdominal pain followed by a sudden large volume discharge. Most commonly, they are a result of ischemic injury, although in rarer cases they may be due to a technical error (fascia or skin is too tight) or underlying disease of the small bowel such as CD or malignancy. Diagnosis should be made by inspection and digital exploration. Hegar dilation in multiple sessions may be effective, but patients often require stoma revision either locally or by a laparoscopic or open intra-abdominal approach.
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PERIOPERATIVE MANAGEMENT
BOWEL PREPARATION
Because of the high bacterial load of the large intestine, elective colorectal surgery without prophylaxis carries a 40% risk of wound infection. This has also been reported as a cause for anastomotic dehiscence. It was previously believed that mechanical lavage (bowel prep) of the gastrointestinal tract would prevent these complications by removing fecal waste and the associated bacterial flora. This involves administration of a large volume of unabsorbed fluid, such as polyethylene glycol or alternatively small volume sodium phosphate, which induces an osmotic diarrhea. Retrograde enemas have been used in distal colon and rectal surgery. Healthy patients usually tolerate these preparations well. However, osmotic agents can lead to dehydration and electrolyte disturbances in more fragile patients.
Although mechanical bowel preparation used to be routine for colorectal surgery, there is debate about its safety and utility. Multiple randomized controlled trials have been completed, with few suggestions of adverse outcomes in both bowel prepped and non-prepped patients. Meta-analyses have shown no differences in outcomes. Specifically, mortality, anastomotic leaks (colo-colonic and colo-rectal), and wound infection rates are similar between the two groups. When a leak occurs, the clinical severity is also not influenced by bowel preparation. There is also no difference between patients treated with preoperative enema versus bowel preparation. This suggests that mechanical bowel preparation can be safely omitted before surgery, especially in patients at risk for prep-related complications.
PERIOPERATIVE ANTIBIOTICS
The use of preoperative parenteral antibiotics significantly reduces surgical wound infection by 75% and should be used routinely. There is no evidence to suggest that infection rates are further reduced by continuing antibiotics postoperatively. Ertapenem has been shown to be superior to cefotetan in preventing surgical site infections in a large randomized controlled trial of 1002 patients undergoing elective colorectal surgery. Parenteral antibiotics are superior to oral antibiotics alone in preventing wound infections, although there is evidence that in patients undergoing bowel preparation those who receive oral antibiotics in combination with parenteral antibiotics have decreased infectious complications compared to those patients who are treated with parenteral antibiotics alone. However, oral antibiotic regimens are poorly tolerated and this is less likely to be important as the use of routine bowel preparation decreases.
DEEP VENOUS THROMBOSIS PROPHYLAXIS
Colorectal surgery patients are at higher risk than general surgery patients for the development of perioperative thromboembolism. In historical series, deep venous thrombosis was diagnosed in 20% of general surgery patients and 30% of colorectal patients without prophylaxis. The rate of symptomatic pulmonary embolism is fourfold higher (0.8% vs. 3.1%). This is related to a variety of factors, including the prevalence of IBD and malignancy in this patient population. Extended operative times, pelvic dissection, and modified lithotomy may also be contributing factors. Subcutaneous heparin and low-molecular-weight heparin are equivalent in reducing both deep venous thrombosis and pulmonary embolism. Low-molecular-weight heparin has a simplified dosing regimen and a decreased incidence of heparin induced thrombocytopenia, however, it is more expensive and there seems to be a dose-related increased risk of bleeding complications. Fondaparinux is a newer Xa inhibitor that has also shown efficacy as a prophylactic agent. There is insufficient evidence to recommend one medication over the other at this time. Sequential compression devices are a useful adjunct.
PAIN MANAGEMENT
There is debate about the most useful postoperative analgesia for colorectal surgery patients. The three most commonly used methods are epidural, spinal, and patient controlled analgesia. Multiple studies have shown decreased subjective pain in patients managed with epidurals, however, this does not translate into better outcomes, and in fact, may lead to increased length of stay. This may be related to the increased use of laparoscopy in colorectal surgery. However, fast track programs to reduce length of stay for colorectal surgery have used short-term epidurals for 24-48 hours with some success. Further study is required to define the impact of these regimens on return of bowel function, pulmonary complications, and mortality.
POSTOPERATIVE NUTRITION
Early initiation of nutrition postoperatively has become the standard of care for patients undergoing colorectal operations. The most studied regimen includes initiating a liquid diet within 24 hours after surgery and advancing as tolerated to a regular diet as opposed to older protocols, which mandated fasting until there was evidence of bowel function in the form of flatus or defecation. Initiating feeding early leads to decreased hospital stay but doesn’t seem to impact other clinical indicators. However, early feeding must be initiated with other interventions such as minimizing fluids and early ambulation.
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Lassen K, Soop M, Nygren J, et al: Consensus review of optimal perioperative care in colorectal surgery: Enhanced Recovery After Surgery (ERAS) Group recommendations. Arch Surg2009;144(10):961-969.
Levy BF, Scott MJ, Fawcett W, Fry C, Rockall TA: Randomized clinical trial of epidural, spinal or patient-controlled analgesia for patients undergoing laparoscopic colorectal surgery. Br J Surg 2011 Aug;98(8):1068-1078.
Lewis SJ, Andersen HK, Thomas S: Early enteral nutrition within 24 h of intestinal surgery versus later commencement of feeding: a systematic review and meta-analysis. J Gastrointest Surg 2009 Mar;13(3):569-575.
McNally MP, Burns CJ: Venous thromboembolic disease in colorectal patients. Clin Colon Rectal Surg 2009 Feb;22(1): 34-40.
Nelson RL, Gladman E, Barbateskovic M: Antimicrobial prophylaxis for colorectal surgery. Cochrane Database Syst Rev 2014 May 9;5:CD001181.
MULTIPLE CHOICE QUESTIONS