General Surgery (Board Review Series) 1st Edition

13

Small Bowel and Appendix

Santosh Krishnan

1. Structural and Functional Anatomy of the Small Intestine
2. Anatomy
3. The small intestine is

• approximately 280 cm long or 160% of body height.

1. The jejunum beginsat the ligament of Treitz, but there is no clear demarcation between the jejunum and ileum.
2. The jejunum is characterized by

• long vasa rectae.
• large plicae.
• thick walls.
• a transparent mesentery.

1. The ileum is characterized by

• short vasa rectae.
• small plicae.
• thin walls.
• fat in the mesentery.

2. Mesentery

• is the tissue that attaches the small intestine to the posterior abdominal wall.
• contains blood vessels, nerves, lymphatics, lymph nodes, and fat.

3. Lymph tissue

• known as Peyer's patchesare abundant in the ileum.

4. The arterial supply(Figure 13-1)

• is from the superior mesenteric artery (SMA).
• The SMA supplies the midgut structures (duodenum distal to the ampulla

P.292

of Vater, pancreas, small intestine, and the ascending and transverse colon).

5. Venous drainage

• is by the superior mesenteric vein.

Figure 13-1. Arterial supply of the small intestine. (Adapted with permission from Nelson RL, Nyhus LM: Surgery of the Small Intestine. Norwalk, CT, Appleton & Lange, 1987, p 16.)

1. Histology

• The small bowel consists of four layers.

1. Mucosaconsists of epithelium, lamina propria, and muscularis mucosa.

• Epithelium turns over every 3–7 days.

2. Submucosacontains vessels, nerves, lymph nodes, and the nervous plexus of Meissner.

• This layer provides the major strength when suturing the small intestine.

3. The muscularisconsists of an outer longitudinal layer and an inner circular layer of muscle fibers.

• The muscularis contains the nervous plexus of Auerbach(myenteric).

4. The adventitiais a layer of visceral peritoneum.
5. Physiology
6. Carbohydrate absorption
7. The daily carbohydrate load

P.293

• is about 350 gof starch, lactose, and sucrose.

2. Initial enzymatic digestion

• is by pancreatic and salivary amylase.

3. Carbohydrates

• are subsequently broken down by the microvilli into monosaccharides.

1. Protein absorption
2. The jejunum

• is responsible for 80%–90% of protein absorption.

2. Proteins are converted

• by acid and pepsin from the stomach to polypeptides.

3. Acid is neutralized

• and pepsin is inactivated as chyme enters the duodenum.

4. Trypsinogen from the pancreas is activated

• to trypsin by enterokinase in the duodenum.

5. Trypsin activates

• chymotrypsin and elastase, which further digest polypeptides.

6. Amino acids and dipeptides are absorbed

• by specific transporters.

1. Fat absorption
2. Emulsification begins

• in the stomach.

2. Fat enters the duodenum

• where pancreatic and biliary secretions mix.

3. Lipase breaks down fats

• into monoglycerides, which are then absorbed by diffusion.

4. In epithelial cells

• triglycerides are resynthesized.
• chylomicrons are formed and enter the lymphatic system through small lacteals.

5. Bile salts are absorbed

• in the ileum.

6. Most of the excreted fat

• comes from desquamated cells and bacteria.

1. Water, electrolytes, vitamins, and mineral absorption
2. Iron

• is absorbed mainly in the duodenum.

2. Most minerals and water-soluble vitamins

• are absorbed in the jejunum.

P.294

3. Vitamin B₁₂

• is absorbed only in the terminal ileum.

4. Of the 5–10 liters

• entering the small bowel, only 500 mL enter the colon.

1. Consequences of small bowel resection

• frequently improve with time.
• can often be adequately treated with dietary changes and antiperistaltic agents.

1. Diarrheacan result from

• water overload of the colon.
• malabsorption (steatorrhea).
• irritation of colonic mucosa by bile salts.

2. Bacterial overgrowth in the small intestinemay occur after resection of the ileocecal valve and can lead to deconjugation of bile salts in the small intestine.
3. Alterations in water and electrolyte transportresult in net secretion instead of net absorption.
4. Fermentation of carbohydratesleads to gas production.
5. These factors lead to bloating, diarrhea, and steatorrhea.
6. Nutritional deficiencies

• B₁₂supplementation should be provided after resecting the terminal ileum.

4. Short bowel syndrome

• is characterized by inadequate length of intestine.
• generally occurs when more than 50% of the small bowel is resected or if less than 100 cmremains.
• leads to diarrhea, steatorrhea, weight loss, nutritional deficiency, and hypergastrinemia.
• If the terminal ileum and ileocecal valveare retained, 70% can be resected.

5. Cholelithiasis

• may result from bile acid malabsorption after ileal resections.

6. Hyperoxaluria and nephrolithiasis

• with calcium oxalate stones may also occur.

1. Normally oxalate is excretedin the stool as insoluble calcium oxalate.
2. Fat malabsorption may lead tocalcium binding of fat in the colon.

• This leaves oxalate free to form water-soluble absorbable salts excreted in the urine.

1. Hormones
2. Secretin

P.295

• is released by duodenal cells in response to acid.
• stimulates water and bicarbonate secretion by the pancreas.

2. Cholecystokinin (CCK)

• is released by intestinal mucosa in response to fat and amino acids.
• stimulates gallbladder contraction, increased bile flow, pancreatic secretion, and relaxation of the sphincter of Oddi.

3. Both CCK and secretin

• inhibit gastrin secretion by the stomach.

1. Motility

• is inhibited by epinephrine.
• is increased by acetylcholine.

1. Migrating myoelectric complex (MMC)

• results in cyclic contractions occurring every 3 minutes during fasting.
• These cyclic contractions are thought to clean the intestine and may be regulated by motilin.

2. The order of recovery of bowel function after surgery is

• small bowel.
• colon.
• stomach.

III. Small Bowel Obstruction (SBO)

1. Pathophysiology of SBO
2. Substances that accumulate proximal to the obstructioninclude ingested fluids, digestive secretions, and swallowed air.

• Most air in dilated bowel is swallowed airand mainly nonabsorbable nitrogen.

2. Fluid enters the lumenbecause distention increases secretion (“third spacing” of fluid).
3. Intravascular volume is reducedresulting in oliguria and hypotension.
4. Bacteria proliferatein the normally sterile small intestine.
5. Signs and symptoms
6. Symptomsinclude

• crampy abdominal pain.
• bloating.
• nausea.
• vomiting.
• failure to pass flatus or stool.

1. Proximal obstruction may present with

P.296

• profuse vomiting without significant distention.

1. Distal obstruction may present with

• less vomiting, but the emesis may be feculent from bacterial overgrowth and distention.

2. Signs of obstructioninclude

• abdominal distension.
• high-pitched bowel sounds.

1. Signs of hypovolemiafrom “third spacing” of fluid may be present.
2. Identification of a herniashould raise suspicion of incarceration.
3. Surgical scars on the abdomenmay suggest adhesion formation.
4. Signs of strangulationinclude

• fever.
• tachycardia.
• peritoneal signs (severe abdominal pain, guarding, rebound).
• leukocytosis.
• These signs suggest that bowel ischemia and necrosis may be present.

1. Causes of SBO (Table 13-1)
2. Mechanical obstruction
3. Adhesions

• are the most common cause of SBO in patients who have had a previous abdominal operation.
• are also the most common cause of SBO in the United States.

1. Hernias

• are the most common cause of SBO in patients who have not had a previous abdominal operation.
• are the most common cause of bowel obstruction in the world.
• may involve the abdominal wall or be internal (see Chapter 10).

1. Tumors
2. Colon cancers

• are the most common tumors causing obstruction.

1. Right-sided colon lesions

• may cause obstruction at the ileocecal valve.

1. Metastatic lesions

• may cause obstruction anywhere along the small bowel.

2. Other locally advanced intra-abdominal tumors

• may cause obstruction (e.g., ovarian tumors).

3. Primary tumors of the small bowel

• may cause obstruction but are rare.

1. Other less common causes of mechanical obstructioninclude

• intussusception.
• ingested foreign body.
• gallstone ileus.

P.297

P.298

P.299

• volvulus.
• congenital lesions (e.g., atresia, web).

Table 13-1. Classification and Differential Diagnosis of Small Bowel Obstruction

Lesion Risk Factors Etiology Characteristics Treatment Misc. Adhesions Previous abdominal surgery Peritoneal inflammation & scarring Obstruction with Hx of previous abdominal surgery NPO & N/G tube decompression; lysis of adhesions if refractory Most common cause of obstruction in United States Incarcerated hernia Presence of hernia Incarceration of small bowel in hernia Obstruction with an unreduced hernia on exam Reduction of herniated bowel and hernia repair Most common cause of obstruction worldwide Neoplasm Hx of malignancy Primary tumors of small bowel, metastatic lesions to bowel Mass on radio-contrast studies, + hemoccult, wt. loss Resection Right-sided colon cancers can mimic small bowel obstruction Stricture Hx of Crohn's radiation, or previous abdominal surgery Chronic intestinal inflammation and scarring Multiple strictured segments may be seen with Crohn's and radiation Resection of segment;stricturo-plasty for Crohn's strictures May occur at surgical anastamosis sites Intussusception Lymphoid hyper-plasia–children; polyps or masses adults Abnormal segment enveloped by peristalsis of normal intestine Intermittent crampy abdominal pain with peristalsis; “currant jelly” stools in children Children–initially barium enema; adults–exploration and resection Frequentlyassociated with malignancy in adults Ingested foreign body Children, retardation, psychosis, abnormal gastric emptying Undigested material;trichobezoars—hair; phytobezoars—plant material Bezoars frequently causeobstruction at the level of the stomach Surgical or endoscopic removal; enzymatic digestion of some types Perforation may occur with some ingested objects Gallstone ileus Hx of cholecystitis/cholelithiasis Obstructing gallstone originating fromcholecystoenteric fistula Gallstone frequently obstructs at ileocecal valve Enterotomy and stone removal or resection; cholecystectomy and repair of fistula site Cholecystoduodenal fistulas are most common Volvulus — Twisting of bowel upon itself Cecal volvulus may cause small bowel obstruction Surgical reduction of volvulus; cecopexy Volvulus may also be associated with other segments of bowel Congenital lesions See BRS Surgical Specialties, Chapter 3 Intestinal malrotation, annular pancreas, webs, intestinal duplication Seen in small children without obvious source of obstruction Treat individual causes Some lesions may not present until adulthood Ogilvie's syndrome (pseudo-obstruction) Recent surgery, serious illness, anticholinergics, narcotics, advanced age Idiopathic colonic dilation Massive proximal colonic dilation without obvious source of obstruction Nonsurgical decompression (i.e., colonoscopy) Small bowel dilation may not be present Hx = history; NPO = nothing by mouth; N/G = nasogastric; + = positive; wt. = weight.

2. Nonmechanical causes of small bowel dilation
3. Paralytic ileus

• refers to a functional loss of intestinal motilityresulting in delayed transit of luminal contents.
• may also mimicSBO.

1. Paralytic ileus may result insmall bowel dilation and accumulation of fluid within the lumen (“third-spacing”).
2. Causesmay include

• surgery(most commonly associated with abdominal operations).
• electrolyte abnormalities(e.g., hypokalemia).
• peritonitis.
• ischemia.
• trauma.
• drugs.

1. Ogilvie's syndrome

• is a form of paralytic ileus that may mimic SBO.
• involves massive acute dilation of the colonin the absence of mechanical obstruction in severely ill and debilitated patients.

1. Predisposing conditionsinclude

• recent surgery.
• infection.
• neurologic or cardiopulmonary disorders.
• metabolic abnormalities.
• drugs.

1. Treatmentinvolves

• transrectal decompression of the colon.

1. Radiographic findings (Figure 13-2)
2. Plain films show

• gas-filled loops.
• air-fluid levelswith a “step-ladder” appearance.
• These findings may be subtle if the obstruction is proximal.

2. Mechanical obstruction versus paralytic ileus
3. In mechanical obstruction

• the bowel distal to the point of obstruction empties because the bowel retains its function.
• high-pitched, active bowel soundsmay be present because peristalsis attempts to overcome the obstruction.

1. In paralytic ileus

• there is uniform gas in the stomach, small bowel, and colon because the bowel has lost its motility.
• bowel sounds are generally infrequent or absent.

P.300

1. Treatment
2. Initial stepsinclude fluid resuscitation and correction of electrolyte abnormalities.
3. Placement of a nasogastric (N/G) tubeand a Foley catheter should also be performed.
4. Further managementinvolves identifying and surgically treating the primary cause of the obstruction.
5. N/G tube decompression and bowel restare effective for some causes of obstruction (e.g., adhesions).

• If the obstruction does not begin to resolvewithin 1–2 days, surgery should be directed at the cause of obstruction.

5. Patients without previous surgerywith SBO require urgent surgical intervention.

Figure 13-2. Radiograph of a small bowel obstruction. (Reprinted with permission from Daffner RH: Clinical Radiology: The Essentials, 2nd ed. Baltimore, Williams & Wilkins, 1999, p 260.)

1. Crohn's Disease

• is a chronic, transmural, inflammatory process.
• is also known asregional enteritis, terminal ileitis, and granulomatous ileocolitis.

P.301

1. Incidence
2. Males and females are equally affected.
3. Peak age of onset is between the second and fourth decades.
4. Incidence in the United States is higher than in Japan.
5. Ashkenazi Jews have a higher incidence than African Americans do.
6. Etiology

• is unknown, but there are many hypotheses.

1. Genetic basis
2. HLA-DR2 and DRB1

• are closely associated with ulcerative colitis but not Crohn's disease.

1. A new marker

• is the MLH1 DNA repair gene.

2. An infectious source

• has been proposed but never proven (i.e., mycobacterial infection).

3. An inappropriate immune response

• may play a role because a favorable response is obtained from corticosteroids and immunosuppressive drugs such as cyclosporine.

1. Pathology
2. Crohn's disease characteristically progressesin a discontinuous manner with affected bowel interspersed with normal bowel (“skip areas”).
3. The most common gastrointestinal tract sites affectedinclude the

• terminal ileum and cecum (40%).
• colon only (35%).
• small bowel only (20%).
• perianal region (5%).

1. Anal involvementmay be characterized by fissures, abscesses, or fistulae.
2. The disease may also affect multiple sites(18%).
3. The mucosamay have a cobblestone appearance.
4. Transmural (full-thickness) inflammationis the most consistent feature.
5. Fibrosismay lead to stricture formation with stiffening of bowel loops.
6. Fistula formationto other loops of bowel, bladder, vagina, or skin may occur.
7. The serosamay have a beefy-red appearance with “creeping” mesenteric fat seen over areas of greatest inflammation.
8. Noncaseating granulomasare found in lamina propria or submucosa in 50% of patients.
9. Clinical features (Table 13-2)

P.302

Table 13-2. Clinical Features of Crohn's Disease

Intestinal manifestations Extraintestinal manifestations* Diarrhea (90%) Arthritis/arthralgia (parallels intestinal disease) Abdominal pain (55%) Erythema nodosum Anorexia Erythema multiforme Nausea Pyoderma gangrenosum Weight loss Pericholangitis/cholelithiasis Perirectal disease (e.g., fistulae, fissure) Renal calculi (calcium oxalate stones) Endocrine disorders (e.g., growth failure, amenorrhea) Ocular disease (e.g., uveitis, blepharitis, corneal ulcers) *Extraintestinal manifestations should raise suspicion for Crohn's disease in patients with intestinal symptoms.

1. Diagnosis
2. The diagnosis is based on

• clinical presentation.
• radiologic findings.
• mucosal appearance.
• histology.
• exclusion of alternative etiologies.

2. Enteroclysis

• is an effective study for diagnosing Crohn's disease.
• helps to define small bowel disease occurring in 90% of patients.

1. Partial obstructionmay be indicated by poststenotic dilation.
2. Stricturesmay be seen as a “string sign” of Kantor.
3. Thickening of mucosal foldsappears as “thumbprinting.”
4. Colonoscopy

• with biopsy of the colon and terminal ileum is also an effective diagnostic tool.

1. Intervening areasmay be normal.
2. Biopsiesmust be obtained from multiple sites.
3. Histologic evidence of diseaseincludes

• fibrosis.
• mononuclear cell and plasma cell infiltrates.
• granulomas.
• architectural distortion.

1. Complications include

• enteric fistulas (29%).
• pelvic abscesses (20%).
• obstruction (9%).
• gastrointestinal hemorrhage (2%).

P.303

• cancer (1%).
• intestinal perforation (1%).
• ureteral obstruction (1%).
• megaloblastic anemia from vitamin B₁₂or folate deficiency secondary to malabsorption.

1. Medical management

• is the primary treatment for Crohn's disease.

1. Sulfa drugs

• are generally first-line therapy for medical management of Crohn's disease.

1. Sulfasalazine

• is broken down to 5-aminosalicylic acid (5-ASA)and sulfapyridine (sulfa antibiotic) by colonic bacteria.

1. 5-ASA

• blocks prostaglandin releaseand decreases inflammation associated with Crohn's.

2. Steroids

• are effective at treating disease refractory to sulfa drugs.

3. Immunosuppressive agents

• used with steroids in a small number of patients with refractory disease include azathioprine, 6-mercaptopurine, and methotrexate.

1. Surgical considerations
2. Surgical therapy for Crohn'shas classically been for treating complications.
3. Indications for surgeryinclude

• obstruction (complete or partial).
• perforation.
• fistula formation.
• the presence of tumor.
• hemorrhage.
• failure of medical management.

3. Surgical resection of small bowel for Crohn's disease

• is generally not considered curative.
• may be associated with a high rate of complications.

1. Short bowel syndrome may resultfrom extensive resections.
2. An alternative to resectionfor stricture disease is stricturoplasty.

• This involves opening a stricture longitudinally and closing the bowel horizontally to increase the lumen size.

4. Generally the recurrence rate

• after surgical resection and primary anastomosis for Crohn's is 70%–75%.

P.304

• Approximately 35% of these patients will require additional surgery.

1. Small Bowel Fistulae
2. Overview
3. Fistulae are abnormal connectionsbetween a hollow viscus and another organ, including the skin.
4. Most are iatrogenicresulting from anastomotic leaks.
5. Contributing factors
6. Bowel inflammation(e.g., Crohn's disease)

• may lead to fistula formation.

1. Malnutrition

• may contribute to poor healing of fistulae.

1. Factors contributing to maintenanceof fistula patency are (FRIEND)

• foreign bodies.
• radiation therapy.
• infection and inflammation (e.g., Crohn's disease).
• epithelialization of the fistula tract.
• neoplasm.
• distal obstruction (i.e., distal to fistula).

4. Classification
5. Descriptions are based onthe origin and termination site (e.g., enterocutaneous).
6. Proximal fistulae (e.g., jejunal)are

• generally high output(> 200 mL/day).
• frequently resistant to closure with conservative therapy.

1. Management
2. Replenishlost fluids and electrolytes.
3. Initiate local skin carefor enterocutaneous fistula.
4. Identify the cause and locationof the fistula and treat if appropriate.
5. Decrease outputwith proximal N/G tube decompression.
6. Provide appropriate nutrition(i.e., parenteral or enteral beyond fistula).
7. Nonsurgical therapy

• Fifty percent will close with nonsurgical therapy.

7. Refractory fistula require resectionin continuity with the diseased bowel.
8. Neoplasms of the Small Bowel
9. Overview
10. Small bowel tumorsare rare (1.5%–6.0% of all gastrointestinal tumors).
11. Benign tumorsare more common than malignant tumors.

P.305

3. Sites of occurrenceinclude the

• duodenum (15%).
• jejunum (25%).
• ileum (60%).

4. The most common clinical manifestations are bleeding and obstruction.
5. Benign neoplasms
6. Epithelial tumors

• include tubular adenomas, villous adenomas, and Brunner's gland adenomas.
• are frequently incidental findings.
• may cause bleeding or obstruction.

1. Duodenal lesions

• can generally be removed endoscopically.

1. Symptomatic jejunal or ileal tumors

• require segmental resection.

2. Stromal tumorsinclude

• lipomas.
• leiomyomas.
• neurogenic tumors (e.g., neurofibromas, schwannomas, gangliomas).
• hemangiomas.

3. Peutz-Jeghers syndrome

• is an inherited syndromewith mucocutaneous melanotic pigmentation and multiple gastrointestinal hamartomatous polyps.
• is the most common syndromeaffecting the small intestine.
• is inherited in an autosomal dominantfashion.
• generally presents with bleedingor obstruction.
• is associated with a high riskof extraintestinal malignancy.

1. Malignant neoplasms

• are rare(Table 13-3).

1. Adenocarcinomasare the most common malignant neoplasm.
2. Sites of occurrenceinclude the

• duodenum (40%).
• jejunum (40%).
• ileum (20%).

1. Wide segmental resectionincluding lymph nodes, is required.
2. Adenocarcinomas of the duodenummay require a pancreaticoduodenectomy (Whipple's operation) [see Chapter 17].
3. Leiomyosarcomasoccur most commonly in the jejunum and ileum.
4. Wide segmental resectionis required.
5. Node resectionis not required because these neoplasms spread hematogenously.

P.306

3. Lymphomas

• are most commonly found in the ileum.
• are the most commonform of extranodal lymphoma.
• are usually non-Hodgkin B-cell lymphomas.
• Treatment includes surgeryand chemoradiation therapy.

4. Carcinoid tumorsmay also occur in the small intestine, especially the ileum.

Table 13-3. Malignant Tumors of the Small Intestine*

Type Site Characteristics Treatment Miscellaneous Adenocarcinoma 40% duodenum, 40% jejunum, 20% ileum Weight loss and abdominal pain. Duodenal lesion–jaundice; jejunum/ileum–obstruction Wide segmental resection with draining nodes Most common malignant tumor of small intestine Leiomyosarcoma Jejunum, ileum Weight loss, abdominal pain, perforation, obstruction, palpable mass Wide segmental resection Node resection not required becausespread is generally hematogenous Lymphoma Ileum GI lymphomas account for 5% of all lymphomas and are the most common extranodal lymphoma Surgery and chemoradiation Most are non-Hodgkin B-celllymphomas Carcinoid 85% appendix, 13% small intestine, 2% rectum Weight loss, abdominal pain, carcinoid syndrome, may be incidental finding Surgery, octreotide for carcinoid syndrome Ileal lesions more likely to metasta size than appendiceal lesions *Malignant tumors of the small intestine are very rare. GI = gastrointestinal.

VII. Miscellaneous Lesions of the Small Intestine

1. Mesenteric ischemia

• may occur with vascular disease of the visceral blood vessels (see BRS Surgical Specialties, Chapter 1).

1. Meckel's diverticulum

• is a congenital diverticulum caused by the failure of obliteration of the omphalomesenteric duct.
• contains all layers of the intestine.
• is found on the antimesenteric border.

P.307

• is usually found incidentally, although bleeding and obstruction may occur.
• Inflammation or infection of the diverticulum may mimic appendicitis.

1. General characteristicsare described by the “rule of 2s.”
2. They are generally found 2 feet from the ileocecal valve.
3. They are present in 2% of the population.
4. Only 2% are symptomatic.
5. Most present by age 2.
6. A diagnostic Meckel's scanuses technetium preferentially taken up by gastric mucosa frequently found in Meckel's diverticula.
7. Other anomaliesinclude

• omphalomesenteric fistulae.
• cysts.

1. Other diverticula
2. Jejunoileal diverticula

• are otherwise rare.

2. Duodenal diverticula

• are relatively common.
• may cause obstructive biliary symptoms if near the ampulla.

VIII. The Appendix

1. Anatomy (Figure 13-3)
2. The appendix

• arises from the posteromedial cecal wall just distal to the ileocecal valve.
• varies in length from 2–20 cm but the average length is 9 cm in adults.
• may be located in the pelvis (35%) or it may be retrocecal (behind the cecum) [5%].

2. The appendicular artery

• is a branch of the lower division of the ileocolic.

3. Surface marking for the appendicular base

• is along a line connecting the umbilicus and the anterior superior iliac spine at a point two thirds the distance from the umbilicus (McBurney's point).

4. The anterior taeniae coli of the colon

• leads to the base of the appendix.

1. Appendicitis

• can occur at any age but is most common from 12–30 years.

1. Pathogenesisinvolves

• obstruction of the appendiceal lumen.

P.308

• increased luminal pressure.

2. Causes of luminal obstructioninclude

• lymphoid hyperplasia (60%, primarily in children).
• fecaliths (35%, primarily in adults).
• foreign bodies (4%).
• tumors (1%).

3. This obstruction leads to

• ischemia, venous thrombosis (gangrenous appendicitis), and finally rupture (perforated appendicitis).

4. Signs and symptoms of appendicitis
5. Abdominal pain

• is the classic sign.
• characteristically precedes nausea and vomiting.
• begins in the periumbilicalregion.
• localizes to the right lower quadrant(RLQ).

1. Rovsing's signis pain in the RLQ with pressure in the left lower quadrant (LLQ).
2. The psoas signis pain on extension of the thigh.
3. The obturator signis pain on flexion and internal rotation of the thigh.
4. Other possible signsinclude

• fever.
• anorexia.
• increased white blood cell count.

Figure 13-3. The appendix. (Adapted with permission from Moore K: Essential Clinical Anatomy. Baltimore, Williams & Wilkins, 1996, p 107.)

1. Symptoms may be subtle

• in the very young or very old.
• when the appendix is retrocecalor pelvic.

P.309

5. Diagnosis of appendicitis

. Differential diagnosis includes

• Crohn's disease.
• mesenteric adenitis.
• ectopic pregnancy.
• tubo-ovarian abscess.
• pelvic inflammatory disease.
• mittelschmerz.

1. Diagnosis is generally based on

• history.
• physical examination findings.

1. Plain films may show

• a fecalith or a “sentinel loop”—a distended loop of small bowel in the RLQ.

1. In complex casesan ultrasound or a computed tomography (CT) scan showing periappendiceal fluid or a thickened appendix may confirm the diagnosis.

• A negative study does not rule out appendicitis.

1. For women

• a pelvic examinationand Βb-HCG must be performed.
• ultrasoundmay be helpful to evaluate gynecologic causes for abdominal pain that may mimic appendicitis.

6. Management of appendicitis

. Intravenous (IV) fluids and broad-spectrum antibiotics should be administered initially.

1. Immediate appendectomyshould be performed through an open or laparoscopic approach.
2. McBurney's incision

• is parallel to the inguinal ligament through McBurney's point.

2. A Rockey-Davis incision

• is also through McBurney's point but is transverse, thus providing a better cosmetic result.

3. If there is rupture

• with generalized peritonitis, the appendix may be removed and IV antibiotics continued.

4. Patients with a periappendiceal abscess

• can undergo delayed appendectomy 6 weeks or longer after treatment of the abscess.

1. Tumors of the appendix
2. Carcinoid tumors

• arise from Kultschitzkycells (neural crest).
• are the most common tumors of the appendix (0.5%).
• are located in the appendix (85%), small intestine (ileum) [13%], and rectum (2%).

P.310

1. Metastasis

• Only 3% of appendiceal tumors metastasize versus 35% of ileal carcinoids.
• Tumors smaller than 1 cm rarely metastasize.
• The risk of metastases is 50% for 1- to 2-cm lesions, and 80%–90% for lesions larger than 2 cm.

1. Presenting featuresmay include weight loss and abdominal pain.

• Many are diagnosed as incidental findings.

1. A desmoplastic reactioncan cause ischemia and obstruction.
2. Carcinoid syndromemay occur with the presence of liver metastases.
3. Symptomsmay include

• flushing.
• diarrhea.
• asthma.

1. Patients may have valvular heart diseaseof the tricuspid and pulmonary valves.
2. A useful diagnostic test ismeasurement of urinary 5-hydroxyindoleacetic acid (5-HIAA), a metabolite of serotonin.
3. Octreotidemay provide symptomatic relief.
4. Appendectomy and resection

• of the mesoappendix is adequate for carcinoids that have not metastasized.

1. A right hemicolectomy should be performed

• if nodes are involved or if the tumor is larger than 2 cm.

2. Mucinous tumors of the appendix (0.2%)

• can be benign or malignant.
• are rarely associated with Trousseau's syndrome(migratory thrombophlebitis).
• Mucin from these tumorsmay disseminate throughout the peritoneum (pseudomyxoma peritonei).

3. Adenocarcinoma

• is rare and behaves similarly to colon adenocarcinoma (see Chapter 14).

P.311

Review Test

Directions: Each of the numbered items or incomplete statements in this section is followed by answers or by completions of the statement. Select the ONE lettered answer or completion that is BEST in each case.

1. A 57-year-old woman with a history of thyroid resection for papillary thyroid carcinoma is admitted after 2 weeks of frequent vomiting. Her only medications include over-the-counter aluminum hydroxide taken occasionally for mild epigastric discomfort. On physical examination, the patient is notably dehydrated. Work-up shows complete small bowel obstruction. Her serum chloride is 90 mEq/dL (low), potassium is 2.9 mEq/dL (low), bicarbonate is 35 mEq/dL (high), and urine pH is low (acidic). Which of the following is the explanation for the alkalotic serum and acidic urine?

(A) Renal bicarbonate loss

(B) Use of aluminum-based antacids

(C) Renal conservation of potassium with hydrogen loss

(D) Stool losses of hydrogen

(E) Excess gastrointestinal absorption of bicarbonate

1–C. Patients with vomiting of long duration frequently lose large amounts of potassium and hydrogen ions found in gastric secretions. In addition, dehydration leads to an aldosterone-mediated resorption of sodium in the distal tubules of the kidney in exchange for secretion of potassium and hydrogen ions into the urine. In the setting of dehydration and severe hypokalemia, hydrogen ions are preferentially secreted in the urine in exchange for sodium to prevent additional loss of potassium. This produces a “paradoxical” acid urine from a patient with hypokalemic metabolic alkalosis. Renal bicarbonate loss would produce serum acidosis rather than alkalosis. Stool losses of hydrogen ions are insignificant, although significant bicarbonate may be lost in patients with severe diarrhea. Aluminum-based antacids also will not cause this electrolyte abnormality.

Questions 2–3

A 53-year-old man with a previous extensive resection of the terminal ileum for a strangulated hernia returns 2 years later without interim follow-up complaining of fatigue, malaise, and weakness. His stools are noted to be heme-negative on physical examination. He is eating without difficulty. His blood smear shows anemia with many hypersegmented neutrophils.

2. Which of the following is the most appropriate therapy for the primary cause of his anemia?

(A) Parenteral iron sulfate

(B) Blood transfusion

(C) Parenteral vitamin B₁₂

(D) Oral vitamin B₁₂

(E) Oral iron sulfate

2–C. The patient most likely has pernicious anemia secondary to vitamin B₁₂ deficiency following ileal resection. Parenteral [intravenous (IV)] vitamin B₁₂ obviates the absorption problem caused by terminal ileum resection. Oral B₁₂ administration may be ineffective secondary to inadequate absorption. Blood transfusion would be inappropriate in this setting and would not address the likely cause of the anemia. Iron supplementation would be appropriate for patients with microcytic anemia secondary to iron deficiency and may provide some benefit in this patient if a concomitant iron deficiency exists. However, hypersegmented neutrophils represent a characteristic sign of B₁₂ deficiency and may occasionally be present without obvious macrocytic changes in red blood cells. IV iron therapy is rarely indicated for treatment of iron deficiency.

3. Which of the following would most likely be associated with nutritional disorders similar to those seen with resection of the terminal ileum?

(A) Peptic ulcer disease

(B) Crohn's disease

(C) Diverticulosis

(D) Colonic ulcerative colitis

(E) Segmental jejunal resection

3–B. Among the choices listed, Crohn's disease frequently affects the terminal ileum and may cause malabsorption of vitamin B₁₂. Peptic ulcer disease may be associated with blood loss anemia but not with vitamin B₁₂ deficiency, although gastric resection for peptic ulcer disease may lead to a deficiency in intrinsic factor with subsequent B₁₂ malabsorption and deficiency. Diverticulosis and ulcerative colitis may both be associated with significant blood loss anemia but are not characteristically associated with vitamin B₁₂ deficiency. Jejunal resection will generally not affect vitamin B₁₂ absorption.

Questions 4–5

During an operation for presumed appendicitis, the patient's appendix is found to be normal. The terminal ileum, however, is found to be markedly thickened and feels rubbery to firm. The serosa is edematous and inflamed and the mesentery is thickened with fat growing about the bowel circumference.

4. Which of the following is the most likely diagnosis?

(A) Ileal Crohn's disease

(B) Meckel's diverticulitis

(C) Ulcerative colitis

(D) Ileocecal tuberculosis

(E) Ileal carcinoid

4–A. Crohn's disease can present acutely, and when it involves the terminal ileum may clinically resemble appendicitis. The bowel in this patient has the characteristic gross findings and inflammatory changes of Crohn's disease including the “creeping fat” within the mesentery. Meckel's diverticulitis can mimic appendicitis but it presents as an inflammatory phlegmon located approximately 50 cm (2 feet) from the ileocecal valve and does not have the bowel changes seen in this patient. Ulcerative colitis is usually confined to the large bowel and, although it may occasionally be associated with inflammatory changes of the ileal mucosa (backwash ileitis), it is generally not associated with full-thickness changes described above. Tubercular ileitis is rare in the United States, although it can produce scarring and stenosis of the distal ileum with enlarged mesenteric lymph nodes. Demonstration of caseation and acid-fast bacilli on lymph node biopsy confirms the diagnosis. Ileal carcinoid would present as a mass in the ileum and would not be associated with the inflammatory changes seen in this patient.

5. After identifying a normal appendix and inflammatory changes are noted to be limited to the terminal ileum, the surgeon plans to perform the appropriate operation. Intraoperatively, which of the following procedures would be the most appropriate to perform in this patient?

(A) Resection of the appendix only

(B) Resection of involved ileum and appendix

(C) Placement of peritoneal drains and appendectomy

(D) Enterotomy with inspection of the ileal mucosa

(E) Right hemicolectomy with lymph node dissection

5–A. When acute Crohn's disease is encountered during exploration for presumed appendicitis, the appropriateness of appendectomy is somewhat controversial. The incidence of enterocutaneous fistula after operation in patients with Crohn's disease is higher than in patients without it, but fistulae usually arise from the diseased ileum and not the appendiceal stump. Therefore, if the stump is not involved, many surgeons perform an appendectomy. This simplifies the differential diagnosis if right lower quadrant (RLQ) pain returns at a later date. The ileum should not be resected unless there is evidence of obstruction, perforation, or fistula formation. Drain placement is not indicated in this patient and may even increase the risk of fistula formation with extensive inflammatory changes in the ileum. In addition, performing an enterotomy may also increase the risk of fistula formation and would be of little, if any, benefit in the management of this patient.

6. A 65-year-old man undergoes a right hemicolectomy with a primary anastomosis for a stage II, right-sided, colon adenocarcinoma. Five months postoperatively the patient presents with a distal ileocutaneous fistula. Which of the following is the most appropriate initial therapy?

(A) Prompt exploration and interruption of the fistula tract

(B) Prompt exploration and bypass of the fistula

(C) A 4–6-week trial of low residue or elemental enteral nutrition or hyperalimentation

(D) Prompt exploration with resection of the involved ileum and primary anastomosis

(E) Ileostomy and ileocecal resection

6–C. Because most fistulas close with proper supportive care and hyperalimentation or low-residue elemental nutrition, this should be attempted before any operation. If needed, the preferred operation is resection of the fistula in continuity with the diseased segment of bowel, followed by reanastomosis. Bypass operations should be avoided, or operations that just resect the fistula or only the involved bowel are not appropriate. Ileostomy and ileocecal resection are not indicated at this point in the management of this patient.

7. A 49-year-old, white man presents to the emergency room with complaints of a 2- to 3-day history of worsening nausea and vomiting. The patient has undergone a previous small bowel resection for Meckel's diverticulitis. The patient's abdomen is distended but nontender. Initial resuscitative measures are taken. Which of the following radiologic studies would be most helpful in the initial evaluation of this patient?

(A) Intravenous (IV) pyelogram

(B) Barium enema

(C) Abdominal ultrasound

(D) Supine and upright abdominal films

(E) Abdominal and pelvic computed tomography (CT) scan

7–D. The simplest test that will show the obstruction is the plain abdominal film. Plain films may show gas-filled loops and air-fluid levels. These findings may be more subtle if the obstruction is proximal. Gas in small bowel outlines valvulae conniventes, which run the entire transverse diameter of bowel. In mechanical obstruction, the distal bowel empties out past the point of obstruction because the bowel retains its ability to move. So a mechanical bowel obstruction has too much gas proximally, and distal to the obstruction it will empty. In paralytic ileus there is a uniform gas pattern in the stomach, small bowel, and colon because the bowel has lost its motility. Intravenous (IV) pyelogram, abdominal ultrasound, and abdominal computed tomography (CT) scanning may frequently be useful in evaluating patients with these symptoms, but they generally should not preclude acquisition of plain radiographs of the abdomen in the setting of a suspected obstruction.

8. Which of the following is a frequent cause of paralytic ileus?

(A) Bezoars

(B) Annular pancreas

(C) Cecal volvulus

(D) Intussusception

(E) Peritonitis

8–E. Among the choices listed, peritonitis is the most likely cause of paralytic ileus. The most common cause of paralytic ileus is abdominal surgery. Bezoars frequently found in the stomach may cause a mechanical obstruction of the stomach. Annular pancreas may cause a mechanical obstruction of the duodenum, while cecal volvulus and intussusception may cause a mechanical obstruction of the small bowel.

9. A 20-year-old college student presents with right lower quadrant (RLQ) pain, fever, anorexia, and leukocytosis. He undergoes appendectomy. Pathological report reveals a 1-cm carcinoid at the tip of the appendix without involvement of the mesentery. Appropriate therapy includes which of the following?

(A) Reexploration and cecectomy

(B) Reexploration and right hemicolectomy

(C) Reexploration with mesenteric node biopsy

(D) Chemotherapy

(E) No further therapy

9–E. Carcinoid tumors of the appendix usually require no more than simple appendectomy. Exceptions are lesions larger than 2 cm, lesions with nodal involvement or serosal spread, or lesions at the base of the appendix near the cecum; right hemicolectomy would be the correct operation for these situations. Cecectomy alone would not be sufficient if the carcinoid tumor met the criteria for further resection. Reexploration with biopsy is not needed because the site of the tumor is known. Chemotherapy is not used for treatment of carcinoid tumors, although medications, such as octreotide, are used to control symptoms of carcinoid syndrome.

10. A 42-year-old woman is found to have a solid, irregular, asymptomatic lesion in the right lobe of her liver during an abdominal computed tomography (CT) scan performed for a trauma evaluation. One week later the patient undergoes percutaneous biopsy of the lesion, which reveals a carcinoid tumor. Efforts to identify the primary source of this lesion are undertaken. Which of the following is the most frequent site of carcinoid tumors?

(A) Jejunum

(B) Liver

(C) Ileum

(D) Appendix

(E) Colon

10–D. The most common site of carcinoid tumors is the appendix. Hepatic metastases may lead to the carcinoid syndrome. One of 500 appendectomies will reveal carcinoid tumor. Carcinoid tumors may metastasize to the liver but are not usually primary. Eighty-five percent are found in the appendix, 13% in the small intestine (ileum), and 2% in the rectum.

Directions: Each set of matching questions in this section consists of a list of four to twenty-six lettered options followed by several numbered items. For each numbered item, select the appropriate lettered option(s). Each lettered option may be selected once, more than once, or not at all.

Questions 11–20

For each clinical scenario, select the correct diagnosis(es).

1. Adhesions
2. Inguinal hernia
3. Intussusception
4. Cecal adenocarcinoma
5. Paralytic ileus
6. Crohn's disease
7. Ogilvie's syndrome
8. Midgut volvulus
9. Bezoar
10. Annular pancreas
11. A 1-year-old with a history of cystic fibrosis presents with 1 day of nausea, vomiting, and intermittent severe abdominal pain. Her mother states that the child has passed stools that are red with clots and mucus. (SELECT 1 DIAGNOSIS)

11–C. Intussusception should be considered in any child younger than 2 years old with intermittent, colicky, abdominal pain. It occurs more commonly in males, and 75% of the cases are in children under 2 years old. At first the vomitus is only gastric contents but eventually becomes bilious. The stool is often described as “currant jelly” (i.e., purple clots with mucus and blood streaking). In most cases, definitive diagnosis and therapy can be effected by barium enema. If this is not successful, operative intervention with reduction of the “lead point” of the intussusception may be necessary.

12. A 67-year-old with a history of thoracic aortic aneurysm repair presents with a 1-day history of bilious vomiting. Physical examination reveals a swollen right groin that is tender and erythematous. The patient is febrile with rebound and guarding. (SELECT 1 DIAGNOSIS)

12–B. Incarcerated hernias represent hernias that are not easily reducible by standard nonoperative means (i.e., mild sedation with application of steady, mild, constant pressure). Incarcerated hernias are the most common cause of small bowel obstruction in the world, with the inguinal region being a frequent site. If the incarcerated hernia has been present for only a few hours, gentle manual reduction may be possible. The presence of a hernia in association with fever, tachycardia, rebound tenderness, guarding, and erythema over the hernia suggests the presence of a strangulated hernia. Strangulation occurs when the perfusion of the incarcerated bowel is compromised, resulting in ischemia and necrosis. This is an indication for immediate operative intervention with resection of the affected bowel and repair of the hernia defect.

13. A 35-year-old woman presents with a 2- to 3-week history of worsening nausea and vomiting. The patient also gives a history of chronic intermittent diarrhea, which she has “learned to live with.” On physical examination the abdomen is distended with hyperactive bowel sounds. A small bowel follow-through reveals multiple consecutive strictures of the distal ileum. (SELECT 1 DIAGNOSIS)

13–F. The finding of multiple consecutive strictures in the distal small bowel is very suggestive of Crohn's disease. Other characteristics of Crohn's may also be present, such as diarrhea, abdominal pain, and perianal disease. Stricture formation and small bowel obstruction is a frequent problem in patients with Crohn's disease.

14. A 47-year-old with a history of melanoma presents with a 2-day history of nausea; vomiting; and intermittent, crampy, abdominal pain. A right lower quadrant (RLQ) mass is noted on physical examination. (SELECT 2 DIAGNOSES)

14–C, D. Melanoma is the most common extraintestinal tumor to metastasize to the small intestine. Metastatic disease to the colon may present with small bowel obstruction (SBO). Obstruction may be secondary to a mass effect of the lesion, causing direct luminal obstruction, or the mass may result in intussusception. Intussusception may present with signs and symptoms of SBO and intermittent, crampy, abdominal pain. In adults with suspected intussusception, early surgical exploration is indicated because many are associated with malignancy. Colonic adenocarcinoma may also present as an SBO. Metastatic colon cancer can affect any part of the intestine while right-sided colon lesions can cause obstruction at the level of the ileocecal valve.

15. A 72-year-old woman, 2 days postoperative from a laparoscopic cholecystectomy, presents with complaints of persistent nausea and vomiting. She denies abdominal pain. On physical examination, the abdomen is distended and without bowel sounds. Nasogastric tube placement and suctioning results in drainage of 1.5 L over the initial hour after placement. Her serum potassium is 2.9 mEq/dL. Abdominal radiograph reveals diffuse dilation of the small bowel. (SELECT 1 DIAGNOSIS)

15–E. Among the choices provided, paralytic ileus is the most likely cause of this patient's symptoms. Although laparoscopic surgery is less likely to be associated with a persistent postoperative ileus versus open abdominal procedures, ileus may still occur. Dehydration with hypokalemia may also contribute to the persistence of a postoperative ileus.

16. A 12-year-old boy with severe mental retardation is brought from a group home with 1 week of nausea, poor feeding, and intermittent vomiting. On physical examination a palpable mass is noted above the umbilicus in the midline. Bowel sounds are normal. Plain films show an enlarged stomach with mottling but without evidence of small bowel dilation. (SELECT 1 DIAGNOSIS)

16–I. A bezoar represents a cumulative mass of ingested nondigestible material [e.g., trichobezoar (hair), phytobezoar (plant material)]. Ingestion of such material may be seen in children or in patients with poor gastric emptying (i.e., after gastric surgery) and may also be associated with certain psychiatric disorders. Bezoars frequently cause obstruction at the level of the stomach and frequently require endoscopic or surgical removal, although some types of bezoars may respond to enzymatic digestion.

17. A 1-month-old presents with a 1-day history of bilious vomiting and abdominal pain. She has not been feeding well and her fontanelles are depressed. She is lethargic and has not had a wet diaper in more than 12 hours. Plain abdominal radiographs reveal a proximal small bowel obstruction. (SELECT 2 DIAGNOSES)

17–H, J. Malrotation with midgut volvulus is a surgical emergency. It usually occurs in infancy (75% in the first month of life). Common findings are bilious vomiting, vascular collapse, and blood from the rectum. An upper gastrointestinal study will best show malrotation. This condition occurs when there is incomplete rotation of the midgut around the superior mesenteric artery. The base of the mesentery is congenitally narrow and the entire midgut can twist on its blood vessels and result in vascular compromise of the bowel. If this condition is ignored, bowel necrosis can occur. In addition, constriction of the second portion of the duodenum by a circumferential segment of pancreatic tissue can cause a proximal obstruction in very young children. This annular pancreas is secondary to abnormal migration of the pancreatic bud during embryologic development. Although this could also cause the symptoms mentioned above, bilious vomiting in a newborn is a malrotation with midgut volvulus until proven otherwise given the severe consequences of this process.

18. A 37-year-old man presents with complaints of worsening nausea, vomiting, and abdominal pain. His history is significant for a previous laparoscopic cholecystectomy for gangrenous cholecystitis 12 years ago. He states that he has had similar symptoms in the past, but they resolved on their own. Plain film of the abdomen shows multiple dilated loops of small bowel. (SELECT 1 DIAGNOSIS)

18–A. In Western countries where abdominal operations are common, adhesions are the most common cause of intestinal obstruction. Peritoneal irritation from any cause causes local outpouring of fibrin and adhesion formation. Substances such as hyaluronidase, steroids, and fibrinolysis have been instilled into the peritoneum without success in preventing adhesions. Conservative management with nasogastric suction may be curative but operative lysis of adhesions may be necessary.

19. A 47-year-old man presents with a 2-week history of worsening nausea and vomiting. The patient has also noted a 10-lb weight loss over the past month. He has had no previous surgery and there are no masses noted on physical examination. Rectal examination reveals no masses, but shows heme-positive stools. Plain film of the abdomen shows multiple air-fluid levels in the small intestine and no air in the colon. (SELECT 1 DIAGNOSIS)

19–D. Right-sided colon cancers may occasionally mimic small bowel obstruction (SBO) by causing obstruction at the level of the ileocecal valve. Recent weight loss and heme-positive stools should raise suspicion for the diagnosis of colon adenocarcinoma. Although this is a rare cause of SBO, a water-soluble (e.g., gastrografin) enema may help rule out such pathology in the absence of signs of more common causes of obstruction.

20. An 82-year-old, retired coal miner is hospitalized in the coronary care unit with an acute myocardial infarction. He has had no previous surgery and there are no masses noted on physical examination. Two days into his hospitalization he develops abdominal distention and crampy pain. Plain films reveal no evidence of small bowel dilation. Barium enema reveals a massively dilated right colon without obvious masses. (SELECT 1 DIAGNOSIS)

20–G. The cause of Ogilvie's syndrome remains unclear but may be related to altered motility of the colon from imbalance of sympathetic and parasympathetic tone to the colon. It is seen mainly in patients hospitalized with severe illnesses. Bowel sounds are usually present and there may be diarrhea. Abdominal radiographs show massive dilation of the colon (predominantly right and transverse) with little or no small bowel dilation. Decompressive colonoscopy is the therapeutic procedure of choice. A generalized paralytic ileus characteristically affects the small bowel in addition to the colon while this variant, Ogilvie's syndrome, may frequently affect the colon without involving the small bowel.