Irritable Bowel Syndrome: Diagnosis

A careful history and physical examination are essential to avoid unnecessary and costly diagnostic testing. The examining physician should attempt to identify foods, nutrients or additives (eg, lactose, sorbitol, saccharin, sucralose), and medications (eg, antacids, calcium channel blockers, anticholinergics) that are related to symptoms. It is also important to look for factors that suggest organic disease and require further diagnostic testing to rule it out. Examples include hematochezia, 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 utility 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 complete blood count (CBC), chemistry panel, thyroid function tests, 24–hour stool collection, and stool testing for ova and parasites.

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.