The Prevalence of Inflammatory Bowel Diseases, Microscopic Colitis, and Colorectal Cancer in Patients with Irritable Bowel Syndrome

The diagnosis of irritable bowel syndrome (IBS) is symptom-based and experts have developed diagnostic criteria for IBS. Distinguishing inflammatory bowel diseases (IBD) from IBS, especially with mild disease activity, can be difficult. Another concern is microscopic colitis (MC). MC and IBS have similar symptoms and a normal endoscopic appearance. Our study investigated the prevalence of patients with IBD, MC, and colorectal cancer among 968 patients that fulfill the Rome III criteria for IBS. Among these patients, four were found with IBD (0.4%) and seven with MC (0.7%). Among the IBD patients, three suffered from Crohn’s disease, affecting the terminal ileum, and one with ulcerative rectosigmoiditis. Of the seven patients with MC, two had collagenous colitis and five had lymphocytic colitis. Two IBS diarrhea-predominant patients had adenocarcin­oma in the sigmoid colon. These patients were a female aged 58 years and a male aged 56 years. We concluded from our study and earl­ier studies that symptom-based diagnosis of IBS may lead to missing a number of other gastrointestinal disorders that require quite different management than that for IBS.