Mack C. Mitchell Jr.
Abdominal Pain
Abdominal pain is one of the most common complaints of ambulatory patients. Acute abdominal pain (onset within 24 hours before the patient seeks help) almost always reflects an organic process. Whether chronic or acute, abdominal pain resulting from an organic cause is more often a symptom of disease of the digestive system than of a process outside the digestive system.
Important characteristics of abdominal pain are the rapidity of onset, apparent severity, location, and accompanying signs and symptoms (e.g., fever, gastrointestinal [GI] bleeding, diarrhea). Chronic pain, if associated with an organic process, may be caused by peptic, gallbladder, or diverticular disease, chronic relapsing pancreatitis
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(primarily in alcoholics), or carcinoma (most commonly pancreatic or colonic). The symptoms and signs that accompany these processes are discussed in a general way in this chapter and more specifically in the chapters devoted to these conditions. Chronic pain that is not associated with a demonstrable organic process is most often caused by the irritable bowel syndrome (see below).
The significance of pain is determined by two major factors: the characteristics of the pain and the characteristics of the patient. The significance of pain to the patient depends on its severity and frequency, the degree to which it interferes with daily life or sleep patterns, and its meaning (both implied and symbolic). Even severe pain can be tolerated for brief periods if it appears infrequently, whereas less severe pain may be less tolerable if it interrupts important activities or disturbs sleep. Pain that has no anticipated end is generally less well tolerated than pain that, even though intense, has a predictable span. The threshold of pain tolerance varies considerably from one individual to another, because of both neurologic and psychological factors. Also, pain that is primarily organic may be reinforced by the secondary psychosocial gains it provides.
Elderly patients with abdominal pain require special attention (1). Even serious underlying conditions may be manifested by minimal subjective complaints and objective signs. For example, cholecystitis, appendicitis, and ruptured appendix are easily missed because pain may not be severe and fever and leukocytosis may be minimal or absent. Therefore, careful evaluation of abdominal pain in the elderly requires repeated abdominal and rectal examinations and serial determinations of body temperature and laboratory tests (e.g., white blood cell and differential counts).
Management of any type of pain can be significantly improved by consideration of certain general principles. For example, reassurance that pain can be relieved by medication or surgery can significantly raise the threshold of tolerance. On the other hand, the existence of severe pain sensitizes patients to additional, less intense pain (e.g., lumbar puncture, venipuncture), and the patient's overreaction to the second pain should not be taken to imply that the primary pain is psychogenic.
Types
Pain involving the digestive system can be visceral, parietal, referred, neurogenic, or psychogenic. Pain caused by metabolic disease is ordinarily visceral or neurogenic.
Visceral Pain
Visceral pain can result from spasm or stretching of the muscle wall of a hollow viscus from inflammation or ischemia or from distention of the capsule of the liver. Tenderness associated with visceral pain (sometimes including rebound tenderness) is often felt directly over the part of the digestive system that is involved, although small bowel tenderness is usually not well localized (except for the terminal ileum). Abdominal viscera are insensitive to cutting, tearing, crushing, and burning.
Parietal Pain
The parietal peritoneum, mesentery, and posterior peritoneal covering are sensitive to forces similar to those that affect the viscera, but the omentum and anterior abdominal wall are less sensitive. Parietal tenderness is more localized than visceral tenderness, and rebound tenderness is experienced over the involved area. Parietal pain that is the result of generalized inflammation (peritonitis) encompasses a large area of the peritoneum. A rigid abdomen, associated with pain, usually implies severe inflammation.
Referred Pain
Both visceral and parietal pain may be referred to a remote site along shared nerve pathways (dermatomes). Gallbladder pain, for example, typically radiates to the infrascapular area; and right diaphragmatic pain, to the right shoulder. Esophageal pain can be confused with the pain of myocardial ischemia because the sites to which the pain radiates may be identical (e.g., the neck and left arm). The more severe the visceral pain, the more likely it is to be referred to the back, as with esophageal spasm or cholecystitis. The skin overlying the dermatome to which the pain is referred may be hypersensitive. Deep palpation of the primary site of the painful organ may intensify the pain, not only locally but also at its referred site. However, the reverse is not true; deep palpation over the referred site does not usually enhance pain over the primary site.
Abdominal Pain Caused by Metabolic Disease
Metabolic disease may produce intestinal pain by a direct effect on the alimentary tract (e.g., when intestinal spasm is induced by porphyria, lead poisoning, or familial Mediterranean fever). In hereditary angioneurotic edema, C1 esterase deficiency may produce intestinal swelling, which can cause pain as a result of partial obstruction or intestinal spasm. On the other hand, metabolic disorders may secondarily produce abdominal pain; for example, hyperparathyroidism can produce a painful peptic ulcer or pancreatitis. Hyperlipidemia also can cause pancreatitis, but it can be associated with abdominal pain in the absence of pancreatic disease.
Neurogenic Pain
Neurogenic abdominal pain (causalgia) is experienced by the patient as a burning sensation along the route of distribution of the nerve and is sometimes associated with
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hyperesthesia. Usually the spinal root is involved by herpes zoster, carcinoma, or arthritis, but peripheral neuropathies caused by operative trauma or diabetes mellitus may also produce neurogenic abdominal pain. There is no relationship of neurogenic pain to digestive function (e.g., eating, defecating).
Psychogenic Pain
Psychogenic pain may represent a conversion reaction that results in the perception of pain when no organic dysfunction exists, or it may result from psychophysiologic reactions characterized by pathologic or physiologic responses to psychological stress (see Chapter 21). For example, emotional stress can lead to painful intestinal spasm in patients with irritable bowel syndrome (see below). This spasm is a measurable physiologic event. Similarly, stress may lead to peptic symptoms as a result of gastric hypersecretion, which also can be quantitated. Pain or tenderness that represents a conversion reaction (emotions converted into somatic complaints) may disappear during periods of distraction. Such pain may be inconsistent and incompatible with known neuroanatomy and neurophysiology.
Historical Clues to Diagnosis
Although successful diagnosis of conditions that cause abdominal pain depends on meticulous pursuit of leads that are provided by the history and physical examination, familiarity with standard questions and examination techniques assists in ensuring completeness. A history of previous episodes of pain, medications taken (e.g., nonsteroidal anti-inflammatory drugs [NSAIDs], warfarin), and the existence of a chronic disease (e.g., diabetes mellitus, diverticulosis) is important. Questions relating to local features include the nature and quality of the pain; its location, radiation, intensity, timing, duration, and course; and the factors that precipitate, aggravate, and alleviate it. Associated symptoms and signs include tenderness, fever and chills, anorexia, nausea and vomiting, diarrhea and constipation, obstruction, borborygmus, rectal bleeding, passing of mucus, jaundice, and genitourinary symptoms. Although aggravation of pain by emotional tension is seen with functional disorders such as irritable bowel syndrome, the pain of many organic disorders can also be accentuated by emotional stress.
Rapidity of Onset of Pain
The temporal development of abdominal pain is an important factor that guides the clinician in evaluation. In particular, pain that develops abruptly or within minutes and becomes rapidly severe is ominous (Table 44.1). Additionally, situations in which a silent period follows the initial symptoms are notoriously deceptive problems. For example, a perforated viscus or an intestinal infarction may be characterized by resolution of the intense initial pain hours after perforation or infarction first occurs and by a recurrence of pain several hours later when peritonitis and volume depletion are well established. If the patient complains of an abrupt onset of severe abdominal pain on the day that he or she visits the clinician, a complete blood count, urinalysis, chest radiograph, plain and upright films of the abdomen, and close surveillance over several hours are imperative.
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TABLE 44.1 Causes of Acute Abdominal Pain According to Rapidity of Onset |
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When the onset of pain is more gradual, many more causes are possible, and considerable judgment is necessary in determining the urgency and direction of the evaluation. Newly experienced abdominal pain, even if it is believed to be innocuous, should never be dismissed
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without followup (at least by telephone) within a few days so that any important new symptoms are not missed. It is best for the clinician to initiate this followup because it obviates the need for the patient to decide whether a change in symptoms is important enough to be of concern.
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TABLE 44.2 Nature and Location of Gastrointestinal Pain |
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Nature and Location of Pain
Esophageal pain is usually described as pressing, constricting, or burning (Tables 44.2 and 44.3). It is usually located in the substernal area and, when severe, radiates through to the back. The location of the pain is a good clue to the location of the underlying disease. Although pain from the lower esophageal region may be referred higher, lesions high in the esophagus do not refer to the lower part of the esophagus (see also Chapter 42).
Gastric pain is usually experienced in the subxiphoid area or in the left upper quadrant of the abdomen. Although gastritis is perceived as a true pain (often burning or cramping in quality), the distress caused by both duodenal and gastric ulceration is experienced as a gnawing discomfort or as a hunger sensation rather than as pain. The discomfort caused by peptic ulcer is often precipitated by fasting and is relieved by eating. The pain of peptic ulcer typically awakens the patient between 1 and 3 a.m. In contrast, pain of gastritis may be aggravated by eating or relieved only momentarily and then subsequently intensified over 10 to 15 minutes. A change from ulcer distress to a burning, boring, or knife-like pain (especially when there is radiation through to the back) is an indication of penetration. Pain that is precipitated by meals also suggests gastric outlet obstruction (often caused by a pyloric channel ulcer) or high intestinal obstruction (see also Chapter 43).
Duodenal pain is felt also in the epigastric area or slightly to the right of it, and it may radiate through to the back. When an ulcer has perforated, the pain appears abruptly in the epigastric region and later settles into the right lower quadrant of the abdomen as gastric contents migrate into the right gutter.
Small intestinal pain is generally diffuse and poorly localized. It is felt in the periumbilical area and, when severe, radiates through to the back. Pain from the terminal ileum may be localized to the right lower quadrant. Uncommonly, it may radiate down the leg. Small intestinal pain is generally crampy, sharp, or aching. Bloating, distention, and dull ache are terms that often are associated with prolonged mechanical obstruction or reflex ileus, whereas more acute forms may be manifested by sharp, steady pain. Associated fever and chills suggest inflammatory bowel disease.
Colonic pain is better localized, often to the lower abdomen. Sigmoid pain is felt in the left lower quadrant, and rectal pain is often described as being in the lower mid abdomen or posteriorly in the rectum. Distention of the splenic flexure of the colon (seen most commonly in patients with the irritable bowel syndrome) from gas produces left upper quadrant or left chest pain that may be confused with the pain of myocardial ischemia. Temporary relief may be obtained by passing gas (see also below, Irritable Bowel Syndrome). Colonic pain generally is crampy or of an aching quality unless perforation occurs, and then it is often severe and constant. Associated fever and chills suggest diverticulitis, diverticular abscess, or ulcerative colitis.
Pancreatic pain is excruciating and constant and usually located in the upper abdomen with radiation through
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to the back, but it may be felt in almost any area of the abdomen. Chronic pancreatic pain (caused by inflammation, pseudocyst, or carcinoma) is similar in nature and location to acute pancreatic pain but may be less severe. Pancreatitis is almost invariably associated with vomiting. If vomiting is not present, other diagnoses (e.g., pancreatic carcinoma) should be considered.
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TABLE 44.3 Differential Diagnosis of Abdominal Pain Caused by Gastrointestinal Disorders |
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Appendicitis often begins as diffuse or periumbilical abdominal pain that intensifies over hours as it settles in the right lower quadrant. The pain of appendicitis is often aggravated by extension of the right leg.
Gallbladder pain generally begins in the right upper quadrant or epigastrium and radiates to the interscapular area or to the right infrascapular area. It is excruciatingly severe, may be aggravated by deep inspiration, and is replaced by a dull, aching sensation that persists for hours after the severe pain subsides. Tenderness can often be elicited by deep palpation under the rib in the area of the gallbladder, especially during deep inspiration. Gallbladder pain often appears several hours after a heavy meal. Associated fever and chills suggest ascending cholangitis (see also Chapter 96).
Hepatic pain localizes over the liver, and a tender liver can be demonstrated by palpation of its edge during deep inspiration or by fist percussion over the lower right rib cage anteriorly (or over the right upper quadrant of the abdomen if the liver is enlarged). Chapters 36and 51 discuss genitourinary pain (e.g., renal colic).
Physical Examination
The patient's general appearance provides clues about the severity, the duration, and often the cause of the underlying condition. The cold sweat and pallor of shock along with the marble skin (superficial vessels seen over blanched skin) indicating vasoconstriction are signs of significant hemorrhage. Tachycardia and perspiration are seen in both shock and sepsis, but the skin in shock is cold and clammy, whereas in sepsis it is warm and moist. Signs of sepsis suggest bacterial enteritis, inflammatory bowel disease, intra-abdominal abscess, cholangitis, pancreatitis, peritonitis, or pyelonephritis.
The position assumed by the patient may be characteristic of a particular disorder. A position of truncal flexure often typifies patients with pancreatitis, whereas patients with gallbladder colic tend to pace or writhe about and appear restless in their unsuccessful attempt to find a comfortable position. This is in sharp contrast to the immobile position assumed by patients with peritonitis, who attempt to avoid even the slightest jarring movement.
Inspection of the abdomen is facilitated by using incident lighting to visualize abdominal asymmetry and to outline masses and pulsations. In thin patients with partial obstruction, peristaltic intestinal movement may be seen through the abdominal wall, and churning peristalsis may coincide with reports of crampy abdominal pain. Flank discoloration (Gray–Turner sign) or periumbilical discoloration (Cullen sign) results from retroperitoneal or intraperitoneal hemorrhage dissecting into the subcutaneous tissues and may indicate hemorrhagic pancreatitis. A strangulated hernia may protrude visibly from ventral defects, from the inguinal area, or into the scrotum, where peristaltic contractions may occasionally be appreciated. Patients with subphrenic abscess or gallbladder disease may have inspiratory pain that results in splinting and avoidance of deep inspiration.
Auscultation should always be performed before palpation so that abdominal sounds may be evaluated before they are altered by palpation. At times borborygmus is audible without the stethoscope. Specifically, one should search for hyperperistaltic or hypoperistaltic sounds, for the high tinkles of obstruction, and for bruits suggesting vascular distortion from aneurysms, atherosclerosis, compression of blood vessels, or invasion of blood vessels (e.g., invasion of the splenic artery in advanced pancreatic carcinoma). Although a silent abdomen implies reflex ileus, bowel sounds may also be quiet or significantly diminished late in the course of mechanical obstruction. Whenever obstruction (especially gastric outlet obstruction) is considered, an attempt should be made to elicit a succussion splash. This is done by placing the stethoscope over the area (e.g., the stomach) and shaking the patient gently but abruptly. A sloshing sound indicates the presence of air and fluid. This finding in the stomach 3 hours or more after eating or drinking indicates delayed gastric emptying or, rarely, marked hypersecretion.
Gentle percussion should precede palpation and is an excellent means for detecting rebound tenderness, masses, and tympany (either generalized or localized) over an area of ileus or obstruction. Because air rises to the space between the liver and the abdominal wall, absence of liver dullness with the patient in a recumbent position is an important finding indicating the presence of free air in the abdominal cavity. Before palpation, it is wise to ask the patient to point to the site of maximum pain. Gentle palpation should at first avoid that site to minimize the chances that muscle guarding will interfere with the examination. The patient should be lying perfectly supine with knees flexed to facilitate relaxation of abdominal muscles. Guarding may be localized over specific lesions (often inflammatory), or there may be marked rigidity if pain is severe, as in perforation or penetration. Subxiphoid tenderness suggests an active ulcer. Tenderness over the liver, especially when the liver edge is brought down against the examining finger by deep inspiration, suggests inflammation in this organ. With gallbladder disease, tenderness is localized to the region of the gallbladder, and with cystic or common duct obstruction, a distended viscus can sometimes be felt as well. Right lower quadrant tenderness is found with appendicitis or with Crohn disease involving the ileum or
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the ileocecal area. A left lower quadrant tender sigmoid cord is felt most commonly with irritable bowel syndrome but can also indicate diverticular disease. A distinct tender mass in the right lower quadrant suggests inflammation (usually Crohn disease) extending beyond the bowel; a similar finding in the left lower quadrant suggests diverticulitis. Board-like rigidity indicates an intra-abdominal catastrophe such as perforation or infarction. Pulsatile masses should be differentiated from laterally expansile masses because the former can represent a mass overlying an artery, whereas the latter implies aneurysmal dilation. When localized perforation has occurred, rebound tenderness may be localized over the area. Hyperesthesia may exist over the segmental distribution of the spinal nerve that innervates the particular area of the viscus. This finding is detected by gently rubbing the fingers over the skin of the associated dermatome.
Rectal examination can be extremely helpful in localizing areas of tenderness as well as in palpating masses through the rectum. Periappendiceal abscesses can sometimes be identified in this manner, as can a perforated diverticulum. On digital examination the finger should complete a circle that includes the entire perirectal area.
Genital and pelvic examination, like the rectal examination, should be performed in all patients with abdominal pain because it can detect hernias as well as genitourinary and other pelvic problems.
If analgesic drugs have been administered, it is useful to re-examine the patient after pain has been relieved to identify masses or localized tenderness that may have been obscured by guarding and rigidity.
Laboratory Tests
A complete blood count, urinalysis, and test for occult blood in the stool are required in every person with serious acute abdominal pain, as are a chest radiograph and plain and upright films of the abdomen. Other laboratory tests should be ordered as indicated by the specific findings.
A low hematocrit value or hemoglobin concentration can call attention to intraperitoneal or retroperitoneal bleeding, whereas hemoconcentration raises consideration of mesenteric vascular occlusion. A high leukocyte count and a high erythrocyte sedimentation rate suggest inflammation or infection. Blood in the urine points to kidney disease as a possible source of pain.
The presence of occult blood in the stool reinforces concern about the GI tract as a source of painful symptoms; it may be an early sign of vascular ischemia or intussusception or a sign of more common lesions such as peptic ulcer, polyp, or inflammatory bowel disease.
Radiology
Plain and upright films of the abdomen are helpful in delineating gas patterns, which may demonstrate displacement of intestine by intra-abdominal masses or may show localized loops of ileus, as with pancreatitis or pyelonephritis. Air is distributed more widely in the small bowel in reflex ileus and in intestinal obstruction. In the latter, the typical stepladder pattern is often encountered on the abdominal radiograph, with slight separation of the loops caused by edema of the wall of the small bowel; an upright film demonstrates air–fluid levels in the dilated loops. Absence of air distal to a specific point suggests obstruction at that point. Volvulus can be diagnosed on the plain film, which demonstrates a sausage-shaped air-filled or air- and fluid-filled viscus coming to an apex. In gastric volvulus, the greater curvature is seen above the lesser curve, and a double air–fluid level is a classic finding, one level being in the lesser curvature of the fundus and the other in the antrum (because of the inverted U-shaped stomach under these conditions). Free air under the diaphragm on the upright film indicates a perforated viscus unless the patient has had recent surgery (at which time air was introduced) or has pneumatosis cystoides intestinalis, in which case a large amount of air may appear subdiaphragmatically from ruptured pseudocysts. The important clue to pneumatosis cystoides intestinalis is the presence of free air in the absence of signs or symptoms of perforation or peritonitis. A radiopaque gallbladder or kidney stones or pancreatic calcification seen on plain films may help corroborate a suspected diagnosis or point attention toward one of these organs.
Contrast studies have been largely replaced by endoscopic procedures in the evaluation of patients with abdominal pain. Endoscopy is both more sensitive and more specific than contrast radiology of the bowel, although it is considerably more expensive. An upper GI series (seeChapter 43) is useful if extrinsic compression on the stomach or duodenum or partial gastric outlet obstruction is suspected at endoscopy.Barium enema (see Chapter 45) can be useful in demonstrating a low site of obstruction and reducing an intussusception. A barium enema should always be preceded by digital examination of the rectum and by proctoscopy to be certain that the rectum is normal (e.g., that there is no rectal carcinoma). When pain is thought to result from gallbladder disease (see Chapter 96) and opaque stones are not visible on plain abdominal films, ultrasonography is an excellent means of demonstrating stones in the gallbladder, although it is less sensitive for detecting stones within the common bile duct. A TcHIDA or PipHIDA radioisotopic study may demonstrate obstruction of the common or cystic duct. This technique requires injection of an isotope and serial views for 1 hour.
Ultrasonography is also useful in showing pancreatic edema or pseudocysts, evaluating a suspected abdominal aortic aneurysm, and evaluating a patient who is difficult to examine for an intra-abdominal mass; this technique has the advantage of avoiding irradiation. Sonography is often unsatisfactory in obese patients and in those with
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metal abdominal sutures because adipose tissue and metal reflect sound waves.
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TABLE 44.4 Ultrasound, Computed Tomographic (CT) Scanning, and Magnetic Resonance Imaging (MRI): Comparison of the Technique and the Patient Experience |
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Computed tomography (CT) is a sensitive means of demonstrating free air, masses, infarcted tissue, cysts, and evidence of inflammation due to diverticulitis, pancreatitis, colitis, or perforation.
Magnetic resonance imaging (MRI) is not used as an initial imaging study of the abdomen but is used selectively to define mass lesions, especially in the liver, kidneys, or adrenal glands, and vascular abnormalities, such as hemangiomas and renal or hepatic vein thrombosis. It is considerably more expensive than a CT scan. HASTE MRI, a newer technique, can demonstrate viscera without movement artifact. It is also effective in showing flowing fluid and therefore can demonstrate partial or complete vascular occlusion or the bile ducts.
Table 44.4 compares the ultrasound, CT, and MRI techniques and the patient experience during the performance of these procedures.
Selective mesenteric angiography should be performed in patients with suspected mesenteric vascular ischemia (particularly in elderly patients with postprandial abdominal pain) or mesenteric vascular occlusion (e.g., women taking contraceptive medication). This is particularly helpful in older patients, because normal arteriographic findings rule out mesenteric vascular disease; on the other hand, occlusion of even two of the three major aortic branches (celiac, superior mesenteric, and inferior mesenteric arteries) can occur without symptoms of mesenteric vascular disease. It may be prudent to hospitalize the patient for this procedure. The patient experience is similar to that described for renal arteriography (see Chapter 67).
Endoscopy
Upper GI endoscopy should be considered the ambulatory procedure of choice to diagnose upper GI disease. Endoscopy should be performed promptly when individuals have abdominal pain associated with upper GI bleeding (see earlier discussion), but these patients should be hospitalized.
Flexible sigmoidoscopy should be performed in any patient with abdominal pain and rectal bleeding or a change in bowel habits and in any patient in whom inflammatory bowel disease (proctitis, ulcerative colitis, Crohn disease) is suspected. Prior preparation for flexible sigmoidoscopy depends on the suspected pathology. Mucosal lesions are best identified after oral cathartics or without preparation. Most enema preparations tend to produce some mucosal edema that may obscure mucosal lesions. Chapter 45 describes the patient's experience during the procedure.
Colonoscopy, like upper endoscopy, requires referral to a gastroenterologist. It should be considered in patients with abdominal pain who have occult rectal bleeding, in those with suspected diffuse colonic inflammatory disease (ulcerative colitis, Crohn disease) or suspected ischemic colitis, and in patients with polypoid lesions on barium enema who require biopsy or, often, resection of the lesion. Colonoscopy cannot be performed within a day or two
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after a barium radiograph of the lower or upper GI tract. Chapter 45 also describes the patient's experience during the procedure.
Treatment
The treatment of patients with abdominal pain depends on the severity of the pain, its rapidity of onset, and the nature of the underlying condition, if known. Severe pain with an abrupt or rapid onset often reflects a GI disorder that will require surgical intervention (Table 44.1). Hospitalization and consultation with a surgeon should be requested immediately in almost all such cases. Less severe pain should not be treated aggressively with analgesic drugs until an attempt has been made to establish a diagnosis, because the pain may abate spontaneously within minutes or hours and not recur. If the pain recurs or persists and the cause is not obvious, the screening tests described in this chapter should be performed. If these tests do not provide a diagnosis, referral to a gastroenterologist is indicated. As a general rule, analgesic drugs may be prescribed to patients with persistent pain, but opiates should be avoided if possible, because they can aggravate the underlying condition. (For example, morphine may aggravate pancreatitis by producing duodenal and ampullary spasm, thus enhancing pancreatic duct obstruction, and opiates or anticholinergics may produce toxic megacolon in patients with active ulcerative colitis.) Furthermore, there is a risk of narcotic addiction if opiates are inappropriately used.
Irritable Bowel Syndrome
Irritable bowel syndrome (IBS), one of the most common medical conditions in primary care practice today, is characterized by chronic abdominal pain and a change in the frequency or character of bowel movements. In Western societies, IBS accounts for nearly 12% of visits to primary caregivers and approximately 28% of all referrals to gastroenterologists (2). For many patients, IBS is a chronic problem that affects many aspects of daily life. The costs of diagnosing and treating patients with IBS are staggering. More than 3 million people visit clinicians each year for the evaluation or treatment of IBS. A study in 1996 reported that the annual cost of IBS-related health care (health care visits, diagnostic tests) in the United States was more than $8 billion (3). That did not include associated indirect costs, such as lost productivity, lost wages, over the counter medications, and copayments for health care, which may be as much as three times as high. Furthermore, IBS is now second only to the common cold as the reason for days missed from work and school (4). Over the last several decades understanding of the pathophysiology of the disorder has improved significantly and provides a basis for establishing diagnosis and treatment.
Definition
In the past IBS was labeled nervous colitis, spastic colitis, mucus colitis, unstable colon, or irritable colon, all of which are inappropriate because they are both imprecise and inaccurate and may cause confusion with more serious disorders like ulcerative colitis. The term “irritable bowel syndrome” may suggest to both patients and clinicians a vague amalgamation of complaints. At times the intestinal tract does seem “irritable” due to underlying abnormalities in gastrointestinal motility and to alterations in visceral sensitivity. However, IBS is actually a fairly specific constellation of findings. For these reasons IBS remains an appropriate and inclusive term.
Criteria for IBS, initially proposed by Manning in 1978, have subsequently been validated in clinical practice (5,6). These criteria were updated and modified by a panel of international experts in Rome in 1998 (7). The Rome criteria define IBS as a chronic disorder of abdominal pain or discomfort present for at least 12 weeks (which need not be consecutive) over the previous 12 months. The pain should have at least two of the following three features: relief by defecation, association with a change in stool frequency, or association with a change in stool consistency. Although the Rome criteria are helpful in identifying patients for clinical trials, they may underestimate the true prevalence of IBS in the general population (8).
Prevalence and Epidemiology
IBS is a worldwide disorder, with a prevalence of 15% to 20% in the United States (2). IBS may present in all age groups, including children. Most patients begin to develop their typical symptoms in the late teenage years or early 20s, although the problem may not be diagnosed for many years. Peak prevalence occurs in the third and fourth decades of life, and then decreases during the sixth and seventh decades of life. Although IBS can be diagnosed at any age, a new diagnosis of IBS should be made cautiously in patients older than 50 years of age, because other diseases (colon cancer, diverticular disease, etc.) may have similar presenting symptoms. For most patients, IBS is a chronic disorder with symptoms persisting to some degree 5 years after diagnosis (9).
The prevalence of IBS is similar in Caucasians and African Americans (10), but is somewhat lower in Hispanics (2). For unknown reasons, women are nearly three times more likely to be diagnosed with IBS than are men (2).
Pathogenesis
Overview
IBS was once thought to represent a nervous disorder of the gut, hence the terms “nervous colitis” or “spastic
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colitis.” However, our concept of IBS has changed considerably over the last 50 years. To label IBS a “colitis” is inappropriate because the disorder affects multiple parts of the GI tract. It is now believed that IBS is a complex disorder in which a number of physiologic processes are involved. These include abnormalities in intestinal motility, alterations in visceral sensory function, and changes in central nervous system (CNS) processing of sensory information. The realization that the gut and the brain are intimately connected now plays a central role in the theory of the pathogenesis of IBS.
Altered Gut Motility
Although a number of different patterns of abnormal intestinal motility have been described in patients with IBS, no one pattern is pathognomonic of the disorder. In general, the signs and symptoms of IBS, and the alterations in GI motility that underlie them, appear to be related predominantly to an exaggeration of normal patterns of intestinal motility.
Enhanced Visceral Sensitivity
Abdominal pain is a critical feature of IBS. A number of studies have demonstrated that patients with IBS have increased sensitivity to pain within the GI tract (11, 12, 13). Many of these studies demonstrated heightened sensitivity to during balloon distention of various locations within the intestinal tract (rectum, sigmoid colon, and ileum). Patients with IBS perceive balloon distention at much lower levels of inflation and describe the distention as more painful than do patients without IBS. This increased sensitivity to pain is not a generalized phenomenon, however, because patients with IBS do not have lower thresholds for somatic pain, when measured by the cold water immersion test. These experiments demonstrate that patients with IBS are very sensitive to stimuli within the gut and suggest that they may interpret normal intestinal function as painful in many circumstances.
Central Nervous System Influences
Some authorities suggest that patients with IBS may process sensory information from the intestinal tract differently than do patients without IBS (2). Additionally, other factors, such as stress, anxiety, or depression, may modulate sensory processing and influence the perception of pain. These findings have significant implications for the treatment of IBS. Therapy focused only on the intestinal tract may be less effective than a multisystem approach.
Other Factors
Clinicians and patients commonly question whether there are unique events that produce IBS or increase the likelihood of developing IBS later in life. Two studies demonstrated that infectious gastroenteritis might increase the likelihood of developing IBS later in life (14,15). Many patients recall the persistence of bloating, abdominal pain, and altered bowel habits after an acute infectious illness (e.g., traveler's diarrhea). The precise mechanism is unknown, but several explanations have been offered (15). An infectious process may injure the enteric nervous system, the intrinsic nerve supply responsible for coordinating peristaltic activity within the gastrointestinal tract. Another possibility involves immune hypersensitivity, where recurrent exposure to an otherwise benign substance might induce inflammation and possibly intestinal dysmotility. Some experts believe an infectious agent could induce a cycle of chronic mucosal inflammation, eventually leading to altered gut motility. However, biopsies of colonic mucosa in patients with documented IBS are not different from specimens from control subjects, an observation that is inconsistent with the hypothesis that mucosal inflammation plays a significant role in the pathogenesis of the disease.
Diagnosis
Most patients with IBS are diagnosed after having symptoms for months to years. The average time between the onset of symptoms and the diagnosis of IBS is just over 3 years (16). The diagnosis of IBS does not need to be difficult or expensive. After a careful interview, physical examination, and a few simple tests, the diagnosis should be apparent, often at the first office visit. In most individuals, IBS should not be a diagnosis of exclusion nor should the patient be told or led to believe that “it is all in your head.”
When strict diagnostic criteria are met and there are no alarm features like unexplained weight loss or GI bleeding (see below), unnecessary diagnostic tests and procedures can be avoided during evaluation of patients with IBS. Several studies have shown that, because of errors in diagnosis, patients with IBS are three times more likely to undergo unnecessary surgery, such as appendectomy, hysterectomy, or exploratory laparotomy, than are patients without IBS (17, 18, 19).
History
The two most common presenting complaints are abdominal pain and altered bowel habits. The pattern of symptoms varies considerably from person to person but remains fairly consistent for a given individual, with changes for an individual occurring predominantly in intensity or frequency of occurrence. A sudden change in this pattern, from chronic diarrhea to constipation, for example, would warrant further investigation. Typically, symptoms are intermittent, with symptom-free periods lasting days, weeks,
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or, rarely, months. However, an occasional patient will have daily symptoms without remission.
By definition, abdominal pain is required for the diagnosis (see Rome criteria, above) of IBS, and must be related to defecation. Pain related to urination, menstruation, or exertion suggests an alternative diagnosis. As noted above, abdominal pain must be present for at least 12 weeks out of the preceding 12 months, although this time does not need to be consecutive. The quality of pain varies among patients, although for most patients the character of the pain remains fairly stable over time. Some patients describe the pain as crampy in nature, whereas others describe it as sharp or burning. The location of the pain may vary from person to person but remains fairly consistent for the same person over time. The pain is more commonly present on the left side of the abdomen than on the right and is most common in the left lower quadrant. Some patients complain of pain in the suprapubic area or describe a deep-seated pelvic pain that localizes toward the rectum. Although the pain is often difficult to localize, some patients describe a belt-like, or band-like, distribution that originates in the left lower quadrant and extends across the midline. The timing of the pain is unpredictable, which is one of the most frustrating aspects of this disorder. The onset of pain does not correlate with any recognized precipitating stressful event; instead, periods of illness may correlate with general periods of stress over many years. It is important to identify life experiences or interpersonal relationships that constitute stress for a particular patient and incorporate this information into the treatment plan. Nocturnal pain is distinctly uncommon and should suggest an alternative diagnosis. However, patients with IBS often suffer from sleep disturbances, and the interruption of sleep may be followed by onset of abdominal pain. Also, patients with IBS often relate that they sleep well but that their typical pain begins immediately upon awakening.
Based on the results of large survey studies, a normal pattern of defecation ranges from three bowel movements per week to three per day. Patients with IBS have altered patterns of defecation, and these altered patterns, although variable from person to person, are fairly consistent for a given individual, changing only in periodicity and intensity. Patients with IBS are usually considered to have one of three patterns of altered defecation: constipation predominant, diarrhea predominant, or alternating constipation and diarrhea. For patients who are prone to diarrhea, many find that the first stool in the morning is of normal consistency. However, subsequent bowel movements become increasingly loose and are associated with significant urgency, abdominal cramps, and flatulence. The urgency and cramps are temporarily relieved by the passage of stool but quickly return and precipitate yet another bowel movement. As bowel evacuation ends, stools are primarily liquid or mostly mucus, leaving patients feeling fatigued. Many patients with IBS are concerned about variations in the size and character of the stool, because they believe these variations represent an anatomic problem within the colon, such as cancer. Formed stools may be compressed and of narrow pencil-sized diameter because of the molding effect of rectosigmoid spasm. In other instances spasm of the colon results in prolonged transit of stool, which produces dehydrated, rocky hard, pellet-like stool, called scybala. Mucus may cover the stools or may be passed alone. Stools may be mistakenly referred to as “diarrhea” when they consist of frequently passed small quantities of soft fragments that are narrow in caliber. Explosive defecation may result from evacuation of gas along with the stool. Fecal incontinence (usually slight staining of the undergarments), which occurs in about 20% of patients with IBS, may result from the repetitive reflex relaxations that occur in association with repetitive spastic distal colonic contractions.
Patients with IBS often describe increased stool frequency in the postprandial period. In addition, many patients also describe increased fecal urgency and more severe lower abdominal cramps and spasms during this same time period. This reflects a heightened gastrocolic reflex, which normally occurs 30 to 45 minutes after a medium- to large-sized meal.
Bloating and gaseous abdominal distention are common complaints of patients with IBS as are complaints of belching, burping, and bloating. However, studies have demonstrated that patients with IBS who have such complaints do not have more intestinal gas than do normal individuals (20). Instead, they have a decreased tolerance to distention from normal amounts of gas, which may be related to hypermotility of their intestinal tract and to a lowered threshold for distention-inducing spasm. Some patients have persistent complaints of severe cramps, pain, and distention in either the left upper quadrant or the right upper quadrant. Symptoms are usually abated by the passage of flatus, often assisted by patients placing themselves in a knee–chest position. These conditions, although uncommon, are referred to as thesplenic flexure syndrome or the hepatic flexure syndrome, respectively. Gas, because it tends to rise, usually forms pockets under the splenic flexure, which is the highest portion of the colon in the upright position. Concomitant rectosigmoid spasm may also prevent the normal release of this gas and thus further exacerbate symptoms.
Patients with IBS also commonly complain of indigestion, heartburn, epigastric pain, and mild nausea. Heartburn, or gastroesophageal reflux disease, is extremely common in the United States, affecting more than 40% of adult Americans (see Chapter 42). Thus, it is not surprising that some patients with IBS also have gastroesophageal reflux disease (GERD). However, many of the other complaints, generally categorized as dyspeptic symptoms, often reflect the same abnormal pathophysiologic processes that occur in the colon and small intestine in patients with IBS.
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Overall, it is estimated that 40% to 50% of patients with IBS have dyspeptic symptoms. This overlap of symptoms reinforces the point that IBS is an appropriate term for this disorder, because it does encompass problems and complaints referable to the entire GI tract.
Several studies have shown a higher prevalence of physical or sexual abuse in patients (primarily women) with IBS than in those without IBS (21). Clearly, a history of abuse is an important factor to consider in patients with functional bowel disorders, and should be discussed in a sensitive manner at an appropriate time in the interview. The timing of this discussion depends on both the patient and the practitioner. Other psychological stressors may play a role as well and should be explored in the evaluation of patients with IBS (2).
Although the symptoms described above are commonly seen in patients with IBS, they are nonspecific and can also be present in other disorders (see Differential Diagnosis, below). However, there are some alarm symptoms or “red flags” that need to be immediately considered because they usually indicate the presence of another disease process. Weight loss is not associated with IBS per se and warrants a more thorough investigation. Anemia, heme-occult positive stool, or frank GI bleeding is not directly associated with IBS and warrants thorough investigation. Large volume or nocturnal diarrhea is not a feature of IBS and suggest an alternative diagnosis. Onset of IBS over the age of 50 is also uncommon. Constitutional symptoms such as fatigue, myalgias, arthralgias, fevers, chills, and night sweats may rarely be seen in patients with IBS, although they are more commonly due to another disorder. Attention should be paid to a family history of inflammatory bowel disease, celiac disease, and any type of GI malignancy.
Physical Examination
A thorough physical examination should be performed at the time of initial evaluation to reassure the patient that complaints are being taken seriously. The physical examination is generally normal. The patient may, however, appear anxious or distressed during the interview and examination. Examination of the lower abdomen may reveal some tenderness or firmness, especially in the left lower quadrant over the sigmoid colon. Since stool is often present in the sigmoid colon, occasionally a fullness may be palpated. Patients with IBS often have spasms in the sigmoid colon, which may account for tenderness. Signs of rebound and guarding should suggest an alternative diagnosis.
A digital rectal examination should be performed in all patients. The presence of an anal fissure may explain a history of rectal bleeding, especially in patients with constipation and straining. The presence of a fistula or significant perianal disease raises the possibility of Crohn disease. Patients with IBS often have some tenderness in the rectum, due to visceral hypersensitivity, rectal spasms, and muscular contractions. However, significant tenderness, evidence of a mass, or the presence of blood in the rectum warrants further investigation.
Laboratory Tests
In patients with IBS the goals of testing are to establish the diagnosis as early as possible, to look for coexisting/alternative diagnoses, and to avoid performing unnecessary tests. A limited number of easily performed tests, coupled with a thorough history and physical examination, can readily diagnose the disorder in most patients. If the patient has predominant symptoms of chronic diarrhea, then stool samples for Giardia antigen and for fecal leukocytes or stool lactoferrin may be helpful. Routine laboratory tests that should be performed include a CBC and erythrocyte sedimentation rate or C-reactive protein. These tests should be normal in patients with IBS. An elevated sedimentation rate or C-reactive protein, a low hemoglobin concentration, or the presence of fecal leukocytes or stool lactoferrin is incompatible with a primary or sole diagnosis of IBS and needs to be investigated by sending stool for culture, examination for ova and parasites, and Clostridium difficile cytotoxin. Patients with diarrhea-predominant IBS should be tested for celiac sprue using serum tissue transglutaminase antibody or anti-endomysial antibody, since several studies have shown a higher than expected prevalence of celiac sprue in patients with IBS (22,23).
In some patients, a more thorough initial evaluation is warranted. In patients with urgency, tenesmus, and discomfort in the left lower quadrant, colonoscopy is recommended to rule out ulcerative colitis, infectious proctitis, microscopic colitis, or cancer. A more thorough evaluation may also be appropriate for patients with a strong family history of inflammatory bowel disease or colorectal cancer or with abnormal findings on physical examination or screening laboratory tests.
Differential Diagnosis
When a patient with IBS is first evaluated and complains of abdominal pain and altered bowel habits, the differential diagnosis is incredibly broad (Table 44.5). However, as the chronicity of symptoms becomes more apparent and if the physical examination is normal, only a few remaining disorders need to be considered.
Many adults develop some intolerance to lactose after the age of 30. If not recognized, continued ingestion of milk or milk products can lead to abdominal bloating, distention, and loose frequent stools, especially in the postprandial period. If the patient is placed on a lactose-free diet and all symptoms disappear, then lactose intolerance can be confirmed (see Chapter 45). However, a lactose-free diet alone will not eliminate all symptoms in most patients with IBS. Some patients with both IBS and lactose intolerance
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have improvement in symptoms of bloating, gas, and more frequent stools with cessation of lactose intake. However, complaints of abdominal pain, rectal spasms and cramps, and fecal urgency persist. Treatment for these symptoms of IBS is discussed below.
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TABLE 44.5 Differential Diagnosis of Irritable Bowel Syndrome |
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Differentiating IBS from inflammatory bowel disease is critical. The absence of anemia and a normal erythrocyte sedimentation rate and a normal physical examination (absence of perianal disease and no evidence of extraintestinal manifestations of IBD) are reassuring.
Many patients are concerned about the possibility of an occult malignancy. Of course, no one test can eliminate the possibility that a malignancy exists, especially in a very early stage. However, the patient should be reassured that with a normal physical examination, normal initial testing (complete blood count, erythrocyte sedimentation rate, heme-occult tests), and the absence of a family history of a GI malignancy, more rigorous invasive testing is unlikely to uncover a malignancy. Reassurance, coupled with routine followup examinations to look for new findings or changes in symptoms, weight, or blood count, is both safe and effective.
Treatment
General Principles
The current treatment of IBS focuses on the relief of symptoms. Treatment begins with the first encounter that should establish a relationship of mutual interest and confidence and that should be thorough enough to demonstrate to the patient that the caregiver has taken the complaints seriously. Attention to the details of all contributing factors, including diet, emotions, professional and interpersonal relationships, and the patient's fears and concerns, provides ample evidence to the patient that these are important factors that must be addressed in the overall treatment plan. The practitioner should avoid dismissing the patient's complaints as being imagined rather than real.
Explaining the present understanding of the pathophysiology of IBS and the factors that influence it emphasizes to the patient that IBS can be managed successfully through cooperation between patient and caregiver. The positive implications of the diagnosis should be underscored, emphasizing that IBS, although chronic in nature, does not lead to cancer or colitis and does not alter life expectancy.
Diet
Even when the patient keeps a meticulous daily log relating onset of symptoms to food intake, it is often difficult to make direct associations with any degree of specificity or certainty. Patients often believe that they have specific food allergies and may limit their diet considerably. It is best to explain to individuals who have postprandial distress that, although some foods may be bothersome, it is usually the act of eating that aggravates or precipitates the symptoms rather than the individual food itself. It is important to stress to these patients that they do not have true food allergies. Some patients find that they are intolerant of certain foods, such as carbonated beverages, caffeine, fatty or greasy foods, alcohol, high-fructose beverages, sorbitol, or certain spices. Although there are no convincing data that these foods as a group are more likely to produce problems than other foods, patients may wish to abstain from the foods that produce unpleasant symptoms.
Some patients with constipation-predominant IBS benefit from a diet that is high in fiber. Bran fiber may increase the size of stool and the frequency of its passage, but may increase flatulence and bloating. Patients should be warned of this effect.
Pharmacotherapy: General Principles
IBS is characterized by complaints of abdominal pain, bloating, and either constipation or diarrhea. Because of the complex interplay between the gut, the enteric nervous system, and the brain it is unlikely that a single agent will ameliorate the symptoms of IBS. Treatment should be
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directed toward relief of the predominant symptom. As an example, at the first visit the patient may wish to focus on the treatment of constipation, whereas at later visits, after some progress has been made in treating constipation, the treatment of pain may become a priority. Since IBS is a chronic waxing and waning disease and because no drug has been shown to be persistently beneficial, medications should be prescribed sparingly and discontinued as soon as possible (Table 44.6).
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TABLE 44.6 Medications Used in the Treatment of Irritable Bowel Syndrome |
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Abdominal Pain
Abdominal pain is the hallmark of irritable bowel syndrome. The underlying cause of abdominal pain in patients with IBS is thought to be due to both heightened visceral sensitivity and abnormal contractions within the intestinal tract. As such, therapy for pain has focused on the use of antispasmodic agents to blunt or minimize smooth muscle contractions within the gut. Although there are ample theoretical grounds for prescribing antispasmodic medications, clinical experience with them has been disappointing. Most studies have not shown significant benefits above placebo, but many of them have been poorly designed and poorly controlled. Nevertheless, some patients do improve with antispasmodic drugs, particularly patients whose symptoms are induced by meals and those with tenesmus. When used for symptoms related to meals, antispasmodics should be prescribed 30 to 45 minutes before meals so that the major benefit of the drug will be available at the time of anticipated symptoms. Patients with tenesmus should take the drug on a regular basis, timing the dose so that it is given as close as possible to 1 hour before anticipated symptoms. There is no evidence that one drug is better than another, but it seems logical to use drugs that have the highest ratio of antispasmodic to antisecretory effect, so that a large dose can be administered to suppress smooth muscle spasm without producing undesirable side effects like dry mouth. Mebeverine, a spasmolytic agent with little or no antisecretory effect, is available in most countries outside of the United States and is prescribed in doses of 100 to 200 mg four times a day (one-half hour before meals if symptoms are meal related). In the United States, dicyclomine hydrochloride (Bentyl) (10 to 40 mg by mouth three or four times a day) or hyoscyamine (Levsin) (0.125 to 0.25 mg by mouth three or four times a day) or Levsin timed releases (0.375 to 0.75 mg by mouth twice a day) should be given as tolerated. The major side effects are tachycardia and orthostatic hypotension. Thus, baseline and followup recordings of pulse rate and blood pressure with the patient seated and standing are very important. Dicyclomine should be prescribed in very small quantities (e.g., 10 mg by mouth three or four times a day) to elderly people who are susceptible to orthostatic changes. Tolerance usually does not develop, but a change to a different anticholinergic may be helpful if benefit decreases. A therapeutic trial should be carried out for at least 3 weeks to test the efficacy of the drug.
Analgesic medications should be avoided if possible and when used should be prescribed in the lowest dose possible. Aspirin and acetaminophen, although generally safe, usually are not effective. Narcotics should not be prescribed to patients with IBS because of the potential for abuse and interference with other treatments (cognitive therapy, behavior modification). Several studies have demonstrated benefits with tricyclic antidepressants (amitriptyline, nortriptyline, desipramine) in patients with IBS. Treatment should begin with a low dose and should be advanced slowly. Effective doses for relief of chronic abdominal pain are generally much less (one-fourth to one-third the usual dose) than those required for depression. Unfortunately, these agents have side effects, most of which are related to their anticholinergic properties. Side effects can limit their therapeutic potential and include dry mouth, dry eyes, sedation, weight gain, cardiac arrhythmias, and hypotension. The selective serotonin reuptake inhibitors (SSRIs) show promise in the treatment
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of IBS patients with chronic abdominal pain. Although more expensive than tricyclic antidepressants, they have fewer side effects, are generally safer, and are well tolerated. There are no large well-controlled studies to confirm that SSRIs relieve chronic abdominal pain in IBS.
Bloating is one of the most difficult complaints to treat. Most medications designed to alleviate gaseous distention are ineffective. However,simethicone (Mylicon), two to four tablets with meals, or activated charcoal, four tablets with meals and at bedtime, can be prescribed as a therapeutic trial.
Tegaserod (Zelnorm) (6 mg by mouth twice a day before meals) acts differently than the nonselective agents described above, because it selectively binds to serotonin receptors in the gut that are directly involved in initiating the peristaltic reflex. Studies have shown that this medication reduces complaints of constipation, increases orocecal transit time, and improves bloating and abdominal pain in up to two thirds of women with constipation-predominant IBS (24).
Constipation
Initial treatment should involve life-style modifications, changes in diet, and use of fiber supplements (see Chapter 45). Patients should be counseled to increase fluid intake to a minimum of 64 ounces per day, eat foods with natural fiber (bran cereals, pears, peaches, stewed prunes, plums), and to regularize bowel evacuation. Many patients find that a daily morning regimen of fiber cereal, stewed prunes or prune juice, and then strong coffee or tea is all that is required. Attempting to defecate 30 to 45 minutes after breakfast may encourage a bowel movement, because this is the time when the gastrocolic reflex is most active.
Fiber supplements (methylcellulose, psyllium, polycarbophil, coarse bran, or ispaghula husk; Table 44.6) are all available over the counter or at health food stores. All these products act as hydrophilic agents to bind water and prevent excess dehydration of the stool. In patients with significant diarrhea, these agents can also bind excess water and increase the bulk of the stool. Controlled trials of fiber supplements have not consistently demonstrated a therapeutic effect (25,26). Up to 20% of patients develop significant bloating and abdominal distention with these agents. Nevertheless, their ease of use, availability, and proven safety make these agents an important part of therapy for IBS. Over-the-counter laxatives such as milk of magnesia or magnesium citrate may be effective for mild constipation.
Prescription laxatives should be considered when dietary supplements and over-the-counter medications fail. Lactulose is a nonabsorbable sugar that can be titrated from a dose of one tablespoon per day to up to three tablespoons three times a day, if necessary. Common side effects include bloating and abdominal cramps. Some patients respond well to the use of polyethylene glycol solutions, either in the form commonly used before colonoscopy (Go-lytely or Nu-lytely) or in a powdered form that can be titrated (MiraLax). Liquid erythromycin (EES suspension, 200 mg per 5 mL), although not commonly used, can be very effective in patients with refractory constipation. Patients are usually begun on a lower dose (50 mg four times a day) and titrated up to 250 mg three or four times a day. Side effects include abdominal cramps, mild nausea, and the possibility of developing oral candidiasis or vaginal yeast infections. However, many patients are quite concerned about the long-term use of antibiotics and prefer to avoid this therapy. Because it stimulates rectosigmoid peristaltic activity,colchicine (0.6 mg tablets) can also be an effective agent. One or two tablets in the morning, 30 to 45 minutes before scheduled bathroom time, can be very beneficial in some patients.
Diarrhea
Patients with loose, poorly formed stools may benefit from low-dose fiber products, as described above, to help absorb excess water and provide more bulk for the stools. Some patients find that the use of these agents in wafer form (e.g., Metamucil wafer), especially at night, is most beneficial, because this formulation does not require additional fluids. Significant diarrhea may respond to loperamide (Imodium), one to two tablets every 6 to 8 hours; its efficacy has been established in a controlled trial (27). Loperamide decreases intestinal transit, thereby allowing more fluid to be absorbed. It also increases external anal sphincter tone and may decrease incontinence and soiling in some patients. Care should be taken to discontinue medication as soon as the diarrhea is controlled to avoid inducing constipation, especially in patients who are prone to having alternating constipation and diarrhea. Loperamide is preferable to diphenoxylate-atropine (Lomotil), a commonly used opiate, because of its longer duration of action and its relative lack of extraintestinal effects. Patients who have strongly diarrhea-predominant IBS and who do not respond to the medications mentioned above may benefit from tincture of opium(deodorized tincture of opium). Patients can start with one or two drops each morning in a small amount of water or juice and slowly increase the dose as necessary. Refractory cases may also respond to cholestyramine, 9 g once or twice a day, which binds bile acids that may play a role in causing diarrhea in patients with IBS.
Alosetron (Lotronex) is a serotonin-3 (5HT3) receptor antagonist that is effective in decreasing both small intestinal and colonic transit (28,29). It reduces the number of loose stools in women with diarrhea-predominant IBS, but has been associated with an increased risk of ischemic colitis (30). For that reason, the Food and Drug Administration (FDA) has limited its use to women with symptoms that are refractory to conventional therapy. Informed consent must be obtained from the patient before the drug can be prescribed.
Chapter 45 discusses the treatment of diarrhea in greater detail.
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Psychological Management
Psychological management begins with the recognition of depression (see Chapter 24), anxiety (see Chapter 22), panic disorder (seeChapter 22), or a somatization disorder (see Chapter 21). Symptoms of IBS often are anxiety provoking and sometimes are perpetuated by social reinforcement (secondary gain). Since an interested primary care provider can perform psychological evaluation and management effectively, psychiatric referral is usually unnecessary. Referral should be reserved for patients who would need expert psychotherapy whether or not they have IBS.
Psychological management is dictated by answers to the following questions: Is there evidence of anxiety, and are the symptoms aggravated by stress? If so, what are the specific stressors? Is the patient depressed? Does gratification from illness behavior reinforce the illness? What misconceptions does the patient have about IBS? Treatment usually requires a multifocal approach, including making the patient aware of the problem, using counseling sessions, cognitive behavioral therapy, stress management, and the use of medications to treat the associated, or underlying, anxiety, depression, or somatization disorder (31).
Alternative Medicines
Many patients resort to natural remedies (e.g., peppermint oil) and herbal medications after traditional medications have failed to provide relief. In these cases, the clinician should ask the patient to bring in the medications or the labels to ensure that the patient is not ingesting harmful substances.
Prognosis
Irritable bowel syndrome is a chronic disorder characterized by episodes of pain, bloating, or diarrhea interspersed with relatively symptom-free periods. Longitudinal studies have shown that more than 75% of patients initially diagnosed with IBS retain that diagnosis 5 years after the initial diagnosis was made (32,33). It is unclear whether the 25% of patients who do not retain the diagnosis of IBS at 5 years have had spontaneous resolution of their symptoms or whether these patients responded to treatment. Most studies report patients who have been referred to specialists for their care and thus may include individuals with more severe symptoms. This referral pattern of more severe patients may account for the chronic nature of the disorder seen in many studies. No data suggest that the diagnosis of IBS increases the likelihood of developing cancer or increases the likelihood of developing some other disease.
Acknowledgment
Special thanks to Dr. Marvin M. Schuster, now retired, for his many tireless years of teaching, research, and patient care in the field of irritable bowel syndrome.
Specific References*
For annotated General References and resources related to this chapter, visit http://www.hopkinsbayview.org/PAMreferences.
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