Symptomatic overlap between microscopic colitis and irritable bowel syndrome: A prospective study

Background: Microscopic colitis and irritable bowel syndrome (IBS) are the common causes of watery diarrhea, abdominal discomfort, and other gastrointestinal symptoms. Previous retrospective data and post hoc analysis of information from a randomized controlled trial have suggested that there is considerable overlap between the symptoms seen in patients with microscopic colitis and the symptom-based criteria for IBS. We sought to study this overlap in a prospective cohort. Methods: A random cohort of patients with biopsy-proven microscopic colitis seen at our institution were administered a symptom questionnaire. Based on their responses, the proportion of patients who met various definitions for IBS was determined. Clinical characteristics of those meeting IBS criteria were compared with those who did not. Results: In the 120 patients who were included, 38% to 58% met the diagnostic criteria for IBS. These patients tended to be younger and more likely female than those who did not meet IBS criteria. Conclusions: Patients with microscopic colitis frequently meet the diagnostic criteria for IBS. Therefore, these criteria are not specific enough to exclude the presence of microscopic colitis. In patients with watery diarrhea, colonoscopy with mucosal biopsies should be performed if symptoms are not controlled by antidiarrheal medications.