Prevalence and incidence of microscopic colitis in patients with diarrhoea of unknown aetiology in a region in central Spain

BackgroundOften previously overlooked, microscopic colitis, including collagenous colitis and lymphocytic colitis, has now emerged as a common cause of chronic diarrhoea.AimsTo evaluate the prevalence and incidence of microscopic colitis in patients with diarrhoea of unknown aetiology.Methods271 consecutive patients who were referred to the General Hospital of Tomelloso from April 2008 to December 2010 for diarrhoea of unknown aetiology underwent a full colonoscopy to obtain biopsy samples to diagnose microscopic colitis on the basis of commonly accepted histological criteria. All patients were classified according to the Roma III criteria for diarrhoea-dominant irritable bowel syndrome.ResultsIn 234/271 consecutive patients with normal endoscopic appearance we observed 32/234 patients with microscopic colitis (30 lymphocytic colitis and 2 collagenous colitis) with a prevalence of microscopic colitis of 48 cases/100,000 inhabitants (95%CI: 30–65) and mean annual standardised incidence of 18 cases/100,000 inhabitants (95%CI: 16.0–20.0). Analysing only the patients that met the Roma III criteria (84/271), we observed 10.7% microscopic colitis diagnosis, with higher risk in the presence of autoimmune disease, seronegative celiac disease and intake of non-steroidal anti-inflammatory drugs.ConclusionsMicroscopic colitis was found in 13.7% of patients with chronic diarrhoea. Microscopic colitis is present in a relevant proportion of symptomatic patients meeting diagnostic criteria for irritable bowel syndrome (10.7%).