Low prevalence of ‘classical’ microscopic colitis but evidence of microscopic inflammation in Asian Irritable Bowel Syndrome patients with diarrhoea

BACKGROUND: There is increasing evidence for the role of microscopic inflammation in patients with IBS. We aimed to examine the prevalence of microscopic colitis and inflammation in Malaysian IBS patients with diarrhoea (IBS-D). METHODS: Consecutive patients who met the Rome III criteria for IBS-D and asymptomatic controls were prospectively recruited. Colonoscopy was performed in all study subjects and systematic biopsies taken from all segments of the colon. The diagnosis of lymphocytic colitis and collagenous colitis was made using previously defined criteria. Patients with post infectious IBS were excluded. RESULTS: 120 subjects (74 IBS-D, 46 controls) were recruited during the study period. In the IBS-D group, the colonoscopic (macroscopic) findings were as follows; normal findings n = 58 (78.4%), diverticula disease n = 5 (6.8%), diminutive polyps n = 9 (12.2%) and haemorrhoids n = 2(2.7%). No subject under the age of 40 had any significant findings. Microscopically, there was only one case (1.3%) with histology consistent with collagenous colitis. However, the IBS-D patients had a higher prevalence of moderate microscopic inflammation (n = 11, 14.9%) compared to controls (n = 1, 2.2%) (p = 0.005). CONCLUSIONS: ‘Classical’ microscopic colitis is uncommon in Malaysian patients with IBS-D but a significant number of adults showed evidence of microscopic inflammation.