Irritable bowel syndrome. Diagnosis in the managed care era.

The common occurrence of irritable bowel syndrome underscores the importance of an accurate diagnostic evaluation without unnecessary expense. A preliminary diagnosis can usually be made with the Manning symptom criteria and additional history data in patients without warning signs of organic disease. A confident diagnosis can often be made with the addition of a physical examination and only limited laboratory and structural studies, such as a proctosigmoidoscopy and complete blood count. Tests that may be indicated in some patients include fecal examination for parasites and occult blood, dietary lactose exclusion or a lactose-hydrogen breath test, and a complete colon structural study. Other tests are occasionally indicated. Routine rectal biopsy and abdominal ultrasonography are unnecessary in patients with only typical symptoms, and large bowel motility testing is not useful. After a confident diagnosis, further testing for recurrent symptoms can be minimized. Investigation for psychosocial factors, while not necessary to diagnose irritable bowel syndrome, is important in treatment and may reduce medical costs. Misdiagnosis can result in unnecessary hysterectomy and other surgery, and it may be reduced by closer collaboration with gynecologists and general surgeons in the evaluation of patients.