RESUMEN
BACKGROUND AND AIM: There is controversy about colonoscopy and taking biopsy from the normal colonic mucosa in patients with a clinical diagnosis of diarrhea-predominant irritable bowel syndrome (D-IBS). This study aims to estimate the prevalence of microscopic colitis (MC) in D-IBS patients and to select patients without the well-known alarming features who will benefit from colonoscopy and biopsies from the normal colonic mucosa. PATIENTS AND METHODS: We performed a cohort cross-sectional study over 6 months duration in a total of 129 patients with Rome III criteria of D-IBS after excluding cases with features of organic diseases. Cases were subjected to colonoscopy and biopsies from the colonic mucosa that seemed normal. RESULTS: Histopathologic examination of biopsies taken from cases with normal colonic mucosa revealed 86 (71.66%) cases with nonspecific colitis, 26 (21.66%) cases with MC and 8 (6.66%) cases with ulcerative colitis. Concomitant immunologic diseases (P=0.00005) and triggering drugs intake (P=0.006) were significantly more common in the MC group. The mean duration of diarrhea in MC patients was significantly longer than that of nonspecific colitis and ulcerative colitis patients (P=0.0006). CONCLUSIONS: Prevalence of MC in D-IBS patients from Upper Egypt is relatively high (21.66%). Concomitant immunologic diseases, possible triggering drugs intake, and long duration of diarrhea are significant risk factors for undiagnosed MC in D-IBS patients.