[Skip to Content]
Access to paid content on this site is currently suspended due to excessive activity being detected from your IP address 35.172.233.2. Please contact the publisher to request reinstatement.
[Skip to Content Landing]
Clinical Review
Clinician's Corner
August 18, 2004

Small Intestinal Bacterial Overgrowth: A Framework for Understanding Irritable Bowel Syndrome

Author Affiliations

Author Affiliation: Division of Gastrointestinal and Liver Diseases, Department of Medicine, Keck School of Medicine, University of Southern California, Los Angeles.

 

Section Editor: Michael S. Lauer, MD, Contributing Editor. We encourage authors to submit papers for consideration as a Clinical Review. Please contact Michael S. Lauer, MD, at lauerm@ccf.org.

JAMA. 2004;292(7):852-858. doi:10.1001/jama.292.7.852
Abstract

Context Irritable bowel syndrome (IBS), which affects 11% to 14% of the population, is a puzzling condition with multiple models of pathophysiology including altered motility, visceral hypersensitivity, abnormal brain-gut interaction, autonomic dysfunction, and immune activation. Although no conceptual framework accounts for all the symptoms and observations in IBS, a unifying explanation may exist since 92% of these patients share the symptom of bloating regardless of their predominant complaint.

Evidence Acquisition Ovid MEDLINE was searched through May 2004 for relevant English-language articles beginning with those related to bloating, gas, and IBS. Bibliographies of pertinent articles and books were also scanned for additional suitable citations.

Evidence Synthesis The possibility that small intestinal bacterial overgrowth (SIBO) may explain bloating in IBS is supported by greater total hydrogen excretion after lactulose ingestion, a correlation between the pattern of bowel movement and the type of excreted gas, a prevalence of abnormal lactulose breath test in 84% of IBS patients, and a 75% improvement of IBS symptoms after eradication of SIBO. Altered gastrointestinal motility and sensation, changed activity of the central nervous system, and increased sympathetic drive and immune activation may be understood as consequences of the host response to SIBO.

Conclusions The gastrointestinal and immune effects of SIBO provide a possible unifying framework for understanding frequent observations in IBS, including postprandial bloating and distension, altered motility, visceral hypersensitivity, abnormal brain-gut interaction, autonomic dysfunction, and immune activation.

×