Microscopic colitis and small intestinal bacterial overgrowth--diagnosis behind the irritable bowel syndrome?

Some patients previously diagnosed with irritable bowel syndrome (IBS) may develop microscopic colitis or small intestinal bacterial overgrowth (SIBO). To estimate the prevalence of microscopic colitis and SIBO in patients with IBS, to evaluate the symptoms and the efficacy of treatment. We examined patients with IBS admitted in our clinic during a three-year period. We identified patients with microscopic colitis by performing total colonoscopy with multiple biopsies from normal intestinal mucosa and those with SIBO by performing a H2-breath test with glucose. We compared the symptoms and the effectiveness of the treatment. Out of the 132 patients initially diagnosed with IBS 3% (n=4) had microscopic colitis and 43.9% (n=58) had SIBO. Diarrhea was the main symptom in patients with microscopic colitis and SIBO (p=0.041), while abdominal pain, abdominal bloating and flatulence were prominent in IBS patients (p=0.042; p=0.039; p=0.048). Specific treatment with rifaximin in SIBO patients negativated H2-breath test in 70.9% cases. Patients suspected to have irritable bowel syndrome should be evaluated for microscopic colitis and SIBO. The proper diagnosis and the specific treatment may cure some difficult cases of the so called "irritable bowel syndrome".