Chronic intestinal pseudo‑obstruction is associated with small intestinal bacterial overgrowth

Purpose Small intestinal bacterial overgrowth (SIBO) is associated with various gastrointestinal diseases; however, its relationship with chronic intestinal pseudo-obstruction (CIPO) remains unclear. This study aimed to determine the prevalence and characteristics of SIBO in CIPO. Methods Between April 2019 and May 2025, we conducted a cross-sectional and prospective cohort study involving 10 outpatients diagnosed with CIPO at our hospital and 10 healthy controls. SIBO was diagnosed using a glucose-loaded hydrogen/methane breath test according to the North American Consensus criteria. We investigated the prevalence and clinical characteristics of SIBO in patients with CIPO. Results The 10 patients with CIPO comprised four males and six females, with a mean age of 48.1 ± 13.6 years. CIPO characteristics were secondary and primary in seven and three cases, respectively; the affected site was the small and large intestine in seven and three cases, respectively. Five of the 10 patients with CIPO were SIBO-positive, and all of them had the hydrogen-type phenotype; SIBO rate was significantly higher in patients with CIPO than in healthy participants (50% vs. 10%, p < 0.01). In CIPO, hydrogen-type SIBO-positive patients tended to have a lower body mass index and stronger diarrhea symptoms than did hydrogen-type SIBO-negative patients. In one case, metronidazole was effective, and the SIBO test result was negative after treatment. Conclusions This is the first report of methane and hydrogen SIBO in Asian patients with CIPO. Hydrogen-type SIBO is more common than methane-type SIBO in Japanese patients with CIPO.