The Prevalence of Small Intestinal Bacterial Overgrowth in Irritable Bowel Syndrome

Purpose: The exact prevalence of small intestinal bacterial overgrowth(SIBO) in patients with irritable bowel syndrome (IBS) is unknown.Various investigators using different methods have reported a prevalence rate of 11to 78% (Am J Gastro 2005; 100: S366, Am J Gastro 2000; 95: 3503–3506). We have previously reported (Hepato Gastroenterology 1998; 45: 1023–1025) that orocecal time using lactulose hydrogen breath test in humans is 55 ± 3 minutes. In the present study we evaluated the prevalence of SIBO in IBS patients using the strcter criterion of increase in breath hydrogen if it occurred 60 minutes or sooner after oral lactulose. Methods: In the period of Dec152005to june 52006, we performed lactulose breath hydrogen test on 52 patients with IBS.The patients afterv a high protein, low fiber dietfasted overnight. A fasting breath hydrogen was recorded with a EC 60 Gastrolyzer (Bedfont Scientific, Medford, N.J.) which has a sealed electrochemical sensor specific for H2. Then they ingested 10 G lactulose in 30 ml of water. Thereafter breath hydrogen was recorded every 5 minutes for the next 75 minutes. A rise of 5 ppm over the baseline occurring at 60 minutes or sooner after lactulose was considered positive for SIBO. Results: There were 52 patients; 18/52(34.6% 0 were men. The mean age was 42.5 years (range 17–76). There were 28/52 (53.8%) patients with constipation dominant IBS (IBS–C); there were 24/52 (46.1%) with diarrhea dominant IBS (IBS–D). SIBO was present in 20/52 (38.4%) of the cases; 9/20 (45%) had IBS–C; 11/20 (55%) had IBS–D which are similar (Chi square p > 0.05). SIBO was present in 9/28 (32.1%) IBC patients which was not different from 11/24 (46%) IBS–D patients (Chi Square p. 0.05) Conclusions: SIBO by our method was found to be present in 38.4% patients with IBS. The prevalence of SIBO was the same in IBS-Cand IBS–D patients.