SIBO

Small intestinal bacterial overgrowth (SIBO) is a condition in which the small intestine harbors an excessive number of bacteria. It is typically diagnosed with breath testing that detects increased hydrogen or methane after carbohydrate ingestion; jejunal aspirate with quantitative culture is the gold standard but rarely performed due to invasiveness.

Causes and risk factors include impaired small-bowel motility (e.g., diabetes, scleroderma), surgical alterations or strictures, reduced gastric acid (such as prolonged proton pump inhibitor use), aging, and conditions like Crohn's disease or chronic pancreatitis.

Symptoms commonly include bloating, abdominal distension, pain or discomfort, excessive gas, and irregular bowel habits (diarrhea or constipation). Malabsorption with weight loss or fat in stool can occur with prolonged disease.

Diagnosis: breath tests (glucose or lactulose) measuring hydrogen and methane levels; a positive result shows a rise above baseline within a typical time frame. Some cases require jejunal aspirate for confirmation.

Treatment: antibiotics such as rifaximin are commonly used; if methane-producing microbiota are present, a combination such as rifaximin plus neomycin may help. Duration is usually 7–14 days. Dietary modification (low FODMAP) may alleviate symptoms; address underlying diseases to reduce recurrence.

Prognosis and recurrence: recurrence is common, and management often focuses on treating underlying motility or structural issues and avoiding contributing factors like unnecessary antibiotic overuse. SIBO is more common in persons with IBS and other gastrointestinal disorders.