Irritable Bowel Syndrome: Diagnosis and Treatment

Diagnosis

• A careful history and physical examination are essential to uncover underlying causes and to avoid unnecessary and costly diagnostic testing.
  
  The examining physician should attempt to identify foods, nutrients or additives (e.g., lactose, sorbitol, saccharin, and sucralose), and medications (e.g., antacids, calcium channel blockers, and anticholinergics) that are related to symptoms.
  
  It is also important to look for worrisome symptoms that suggest gastrointestinal disease, which may require diagnostic testing. Examples include bloody stools, weight loss greater than 10 pounds, family history of colon cancer, recurring fever, anemia, and severe diarrhea.
  
• The Rome II criteria have been designed to create a standardized system for diagnosis, but the usefulness of these criteria has not been fully established. The criteria include:
• At least 12 weeks of continuous recurrent abdominal pain that is relieved by defecation, and/or a change in the consistency, frequency, or form of stool
  
• Abnormal stool passage (straining, urgency, or feeling of incomplete evacuation)
  
• Passage of mucus
  
• Bloating or abdominal distention
• In appropriate patients, laboratory studies may include blood testing, thyroid function tests, 24–hour stool collection, and stool testing for infection.
  
• Colonoscopy may be useful to rule out inflammatory bowel disease and colon cancer, especially in patients over 50. In younger patients with symptoms of irritable bowel syndrome, colonoscopy is not usually necessary.

Treatment

There is no specific cure. However, nutritional interventions and medications are effective in some patients to reduce the symptoms.

• Avoid possible food triggers, including lactose and artificial sweeteners (e.g., sorbitol, saccharin, and sucralose).
• Diarrhea can be treated with loperamide (Imodium), cholestyramine (Questran), or other antidiarrheal medications.
• Constipation can be treated with fiber supplementation, laxatives, or other medications.
• Abdominal pain may respond to antispasmodic agents (e.g., mebeverine, dicyclomine, or hyoscyamine) or tricyclic antidepressants (e.g., amitriptyline).
• Recent studies suggest that antibiotic therapy (e.g., rifaximin) can be useful in certain cases, especially in patients with bacterial overgrowth and diarrhea.
• Psychological interventions are often helpful. A recent review of randomized, controlled trials of psychological treatments found that eight out of 12 treatments showed positive responses, mainly reductions in pain and diarrhea. Treatment guidelines published by the American Gastroenterology Association suggest that cognitive–behavioral treatment, interpersonal psychotherapy, hypnosis, and stress management/relaxation are effective in reducing abdominal pain and diarrhea.