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Pathophysiology
Irritable bowel syndrome may be caused by alterations in bowel motility and visceral hyperalgesia have been demonstrated. Stress, gut neuropeptides and neuroendocrine connections to the brain are under investigation. There is a higher frequency of psychiatric diagnoses in patients with irritable bowel syndrome who
Diagnosis
Irritable bowel syndrome is a functional bowel disorder. Functional gastrointestinal disorders can present with several constellations of symptoms for which an organic cause may not be identifiable. Lactose intolerance, the use of products that contain sorbitol or fructose and the use of medications, such as laxatives and antacids, that affect the intestines may be easily treatable causes of diarrhea, cramps or bloating. Approximately 52 percent of
A history of verbal or sexual abuse may also be important. Up to 50 percent of individuals with symptoms of irritable bowel syndrome reporte such a history. Other psychosocial factors and stressors should be identified, since it has been suggested that stress can exacerbate the symptoms of
Findings such as occult blood, fever, weight loss, anemia or other biochemical abnormalities should be investigated for more specific causes. The occurrence of pain or diarrhea that interferes with normal sleep patterns or awakens the patient from sleep is suggestive of
Diagnostic Criteria for Irritable Bowel Syndrome
Persistence or recurrence of the following symptoms for a period of1. Abdominal pain or discomfort, relieved with defecation or associated with a change in the frequency or
2. An irregular (varying) pattern of defecation at least 25 percent of the time, with two or more of the following:
a. Altered stool frequency
b. Altered stool form (hard stool or loose, watery stool)
c. Altered stool passage (straining or sensation of urgency, feeling of incomplete evacuation)
d. Passage of mucus
e. Bloating or a feeling of abdominal distention
Clinical evaluation and tests
Symptoms suggestive of biliary or upper gastrointestinal disease should be evaluated with an appropriate barium, endoscopic, ultrasonographic or nuclear evaluation. If diarrhea is a major component, a colonic biopsy for microscopic (lymphocytic) or collagenous colitis should be performed. A relationship of symptoms to the menses may suggest endometriosis.
Studies with negative findings not only help to confirm the diagnosis of irritable bowel syndrome but also provide reassurance for the patient. It is
Treatment
Stratifying patients into those with predominant constipation or diarrhea, or pain, gas and bloating can be a useful way of directing treatment. Specific foods that aggravate symptoms sometimes can be identified and eliminated from the diet. Up to 50 percent of patients with irritable bowel syndrome
In most patients, constipation can be managed by supplementing the amount of dietary fiber to include at least 20 to 30 g per day. Adequate supplementation often can be achieved with one-half cup to one bowl per day of wheat bran or one-half to one tablespoon of psyllium twice daily. For patients who are unable or unwilling to take fiber supplements, a detailed listing of the fiber content of various foods can be helpful. A trial of
A bowel-training regimen may be helpful in patients who continue to have constipation. A 15- to 20-minute period should be allocated every day (typically after breakfast) for sitting on the toilet without attempts at straining. Patients should be discouraged from abusing laxatives. If laxatives must be used, osmotic laxatives are preferred. Lactulose (30 to 60 mL) or less expensive agents such as magnesium hydroxide (Milk of Magnesia) or
Antidepressants. Several controlled and uncontrolled trials suggest that antidepressants help manage pain in patients with irritable bowel syndrome. Benefits of antidepressant therapy may included improvement in anxiety or depression, alteration of visceral nociception and
Course to Follow When Initial Treatment Fails
Despite reassurance and conservative treatment, many patients with irritable bowel syndrome continue to have symptoms. In rare cases, a reappraisal of the diagnosis may be indicated, and additional appropriate tests should be performed. This approach, which is often encouraged by patients, must
A consistent approach should be used, with regular, brief appointments with the patient, and the patient should be helped to accept realistic goals for treatment. These measures may assist in strengthening the physician-patient relationship and minimizing the
Pelvic floor dysfunction and colonic inertia must be considered in patients withintractable constipation. Several tests may be used to assess anorectal and pelvic floor function. Delayed colonic transit can be measured in several ways. One technique uses radiolabeled resin pellets that are delivered to