The prevalence of small intestinal bacterial vergrowth in irritable bowel syndrome.

BACKGROUND/AIMS: This study was performed to evaluate the prevalence of small intestinal bacterial overgrowth in patients with irritable bowel syndrome by doing a lactulose breath hydrogen test. METHODOLOGY: Two hundred and fifty-eight patients with irritable bowel syndrome were referred to us for the performance of lactulose breath hydrogen test. After an overnight fast, fasting breath hydrogen in parts per million was recorded using a portable analyzer which has a sealed electrochemical sensor for hydrogen. After an oral dose of 10 g lactulose, breath hydrogen concentration was recorded every 10 minutes for 70 minutes. An increase of 5 parts per million in hydrogen over the baseline that occurred 60 minutes or sooner after lactulose was considered positive for small intestinal bacterial overgrowth. RESULTS: There were 75 (29.0%) men and 183 women (70.9%). The mean age was 49.0 (range 16-87) years. Small intestinal bacterial overgrowth was found in 89 (34.5%) of patients. The prevalence of small intestinal bacterial overgrowth in men (30.6%) was similar to that in women (36.0%). Small intestinal bacterial overgrowth was more common in diarrhea dominant irritable bowel patients (58.4%) compared to constipation dominant irritable bowel patient (41.5%). The frequency of small intestinal bacterial overgrowth was higher in women compared to that in men. CONCLUSIONS: Small intestinal bacterial overgrowth was found in 34.5% of patients with irritable bowel syndrome. Small intestinal bacterial overgrowth was more likely to be present in diarrhea dominant irritable bowel patients compared to those with constipation dominant irritable bowel patients. Although the prevalence of small intestinal overgrowth was similar in men and women the frequency of small bowel overgrowth in women was higher compared to that in men.