Small intestinal bacterial overgrowth, or SIBO, produces digestive symptoms that mirror irritable bowel syndrome so closely that many patients spend years receiving the wrong diagnosis. Gastroenterologists now recognize SIBO as a distinct condition requiring targeted treatment.
In SIBO, bacteria that normally live in the colon migrate into the small intestine, where they ferment food and produce gas. This fermentation creates bloating, abdominal pain, diarrhea, and constipation. Nausea and fatigue often accompany these symptoms. The overlap with IBS leaves patients confused and frustrated.
The key difference lies in where the problem originates. IBS involves abnormal gut motility and visceral sensitivity without necessarily involving bacterial overgrowth. SIBO involves an actual microbial imbalance. Dr. Mark Pimentel at Cedars-Sinai Medical Center has documented how breath testing can identify SIBO by measuring hydrogen and methane levels after patients consume lactulose or glucose. These gases indicate bacterial fermentation in the small intestine.
Several factors trigger SIBO. Food poisoning can disrupt the intestinal barrier. Adhesions from abdominal surgery slow intestinal movement. Medications like proton pump inhibitors reduce stomach acid, allowing bacteria to survive longer. Conditions affecting motility, including diabetes and Parkinson's disease, increase SIBO risk.
Treatment depends on the underlying cause. Antibiotics like rifaxomicin target the overgrown bacteria. Dietary changes matter too. Low-FODMAP diets restrict fermentable carbohydrates that feed bacteria. Prokinetic agents help restore normal intestinal movement.
The distinction between SIBO and IBS matters because treatment approaches diverge significantly. A patient with SIBO may not respond to standard IBS therapies. Getting an