[Prevalence of microscopic colitis in patients with irritable bowel syndrome with diarrhea predominance].

BACKGROUND: Microscopic colitis (MC) and irritable bowel syndrome with diarrhea (IBSD) have a similar clinical and endoscopic presentation. The prevalence of MC in Mexican patients with IBS-D is unknown.

OBJECTIVES: To find out the prevalence of MC in patients with IBS-D and compare it with the one observed in patients with IBS with constipation (IBS-C).

METHODS: All patients with IBS (Rome III) seen consecutively from January 2008 to August 2010 were included. Those with organic disease, alarm signs, mixed IBS or unsubtyped- IBS (Rome III) were excluded. Colonoscopy with biopsies was performed in all patients that were examined by two pathologists who did not know the clinical characteristics of the subjects. MC was defined according with the universally accepted histological criteria.

RESULTS: 155 patients with IBS-D and 145 with IBS-C were studied. Both groups were matched from the standpoint of age, gender ratio and time course of disease. MC was detected in 28 patients with IBS-D and in one with IBS-C (18% vs. 0.7%, p <0.0001). Fifteen patients with lymphocytic colitis and 14 with collagenous colitis were detected. The endoscopic appearance of the colon mucosa was normal in 20 of the 29 patients with MC (69%).

CONCLUSIONS: The prevalence of MC in patients with IBS-D was 18%, significantly higher than the one observed in patients with IBS-C. Colonic mucosa had a normal appearance in most of the patients with MC. Systematic biopsies are recommended in patients with IBS-D.