Small Intestinal Bacterial Overgrowth in IBS

AUGUST 01, 2005

Small intestinal bacterial overgrowth (SIBO)—detected using the lactulose breath test—and sugar malabsorption—detected using hydrogen lactose, fructose, and sorbitol breath tests—may have roles in irritable bowel syndrome (IBS). In Alimentary Pharmacology and Therapeutics (June 2005), Gabriella Nucera, MD, and colleagues assessed the influence of SIBO on hydrogen lactulose and sugar breath tests in 98 IBS patients before and after eradication therapy.

The lactulose breath test results were positive for 64 (65%) of the 98 patients. These patients had significantly higher positive results on lactose (P < .05), fructose (P < .01), and sorbitol (P < .01) breath tests, compared with patients without SIBO. After antibiotic treatment, eradication of bacteria resulted in a significant reduction in positive findings on sugar breath tests (17% vs 100%, 3% vs 62%, and 10% vs 71%, respectively; P < .0001), suggesting that sugar malabsorption findings may be falsely positive in patients with SIBO. Eradication of SIBO may normalize sugar breath levels. Therefore, tests for SIBO should be conducted before other sugar breath tests to avoid sugar malabsorption misdiagnosis.