Frequency and Predictors of Small Intestinal Bacterial Overgrowth in Patients with Functional Dyspepsia

Functional dyspepsia (FD) is a disorder of gut-brain interaction characterized by chronic upper gastrointestinal symptoms without a structural explanation for those complaints. Small intestinal bacterial overgrowth (SIBO) has been proposed as one mechanism that may contribute to symptoms in a subset of affected patients. We assessed how often SIBO was present in FD and examined variables associated with SIBO positivity.

This case-control study was conducted at a tertiary gastroenterology center in India. Thirty adults fulfilling Rome IV criteria for FD and 30 age- and sex-matched healthy controls were enrolled. All participants underwent glucose hydrogen-methane breath testing. Clinical and laboratory variables were compared between SIBO-positive and SIBO-negative patients, followed by multivariable analysis.

Among patients with FD, epigastric pain syndrome was the most frequent subtype (53.33), followed by overlap FD (43.33) and postprandial distress syndrome (3.3%). Small intestinal bacterial overgrowth was identified more often in cases than in controls [8/30 (26.6%) vs 1/30 (3.3%); p = 0.026]. On unadjusted analysis, bloating, belching, flatulence, and higher basal hydrogen values were associated with SIBO positivity. None remained independently significant after adjustment.

Compared with healthy controls, patients with FD had a higher prevalence of SIBO. Although a few symptom-related variables tracked with SIBO on univariate testing, no independent clinical predictor was established. Larger studies are required before symptom-based selection of FD patients for SIBO testing can be advised.