Small Intestinal Bacterial Overgrowth in IBS

Small intestinal bacterial overgrowth (SIBO)—detected using the lactulosebreath 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 onhydrogen lactulose and sugar breath tests in 98 IBS patients before and aftereradication 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 withoutSIBO. After antibiotic treatment, eradication of bacteria resulted in a significantreduction in positive findings on sugar breath tests (17% vs 100%, 3% vs 62%,and 10% vs 71%, respectively; P < .0001), suggesting that sugar malabsorptionfindings may be falsely positive in patients with SIBO. Eradication of SIBO maynormalize sugar breath levels. Therefore, tests for SIBO should be conductedbefore other sugar breath tests to avoid sugar malabsorption misdiagnosis.