Pilot Study on Gas Patterns of Irritable Bowel Syndrome and Small Intestinal Bacterial Overgrowth Following Ingestion of Lactulose

Background & Aims: Fermentation site and increasing time of symptomatic gas would be different between irritable bowel syndrome (IBS) and small intestine bacterial overgrowth (SIBO). The aim of this study was to determine the time for increase in abdominal gas following ingestion of lactulose and the possibility of differential diagnosis of SIBO and IBS. Methods: A prospective study was conducted on a series of IBS patients (n = 14) who were referred to the Oroku-Hospital (Okinawa, Japan) from June 6, 2014 to December 30, 2014. Imaging was first performed in early morning after fasting. After ingestion of lactulose, 1 - 4 plain abdominal radiographs were taken for investigation of increased gas during the indicated timeframe. Regions of interest of the gas areas were highlighted on the images obtained. Gas images were divided into three areas, the stomach, small intestine, and large intestine, and each total area was calculated. Results: At a dose of 10 g lactulose and an observation time of two hours, patients displayed no symptoms, and the gas volume was only slightly increased. However, when the dose of lactulose was increased (13 g/50 kg), and the observation time for the lactulose challenge was extended to 240 - 300 minutes, the results clearly demonstrated an increase in the gas produced in IBS patients. Conclusions: An increased dose of lactulose coupled with an extended observation time for the lactulose challenge clearly demonstrated an increase in the gas produced in IBS patients. Alterations in diet rather than antibiotics might reduce IBS symptoms.