High Prevalence of Small Intestinal Bacterial Overgrowth in Patients with Morbid Obesity: A Contributor to Severe Hepatic Steatosis

Background With the increasing prevalence of obesity, non-alcoholic fatty liver disease (NAFLD) has become a major cause of liver diseases. Small intestinal bacterial overgrowth (SIBO) could be related to NAFLD. Our aim was to determine the prevalence of SIBO and its relationship with liver lesions in morbidly obese patients. Methods A glucose hydrogen (H₂) breath test (positive if fasting breath H₂ concentration > 20 ppm and/or an increase of > 10 ppm over baseline within the first 2 h) was performed in obese patients referred for bariatric surgery (body mass index BMI] >  40 kg/m² or >  35 in association with comorbidities) and in healthy non-obese subjects. In obese patients, a surgical liver biopsy was performed. Results One hundred and forty-six patients (129 women, age mean±SE]: 40.7 ± 11.4 years) were prospectively included in the study. The mean BMI was 46.1±6.4 kg/m². A liver biopsy was available in 137 patients and a breath test in 136. The frequency of positive breath tests was higher in obese patients (24/136, 17.1%) than in healthy subjects (1/40, 2.5%; P=0.031). In the univariate analysis, SIBO was not associated with clinical variables, but tended to be associated with more frequent severe hepatic steatosis (26.3 vs. 10.3%, P=0.127), whereas the frequency of sinusoidal or portal fibrosis, lobular necrosis and non-alcoholic steatohepatitis (NASH) were not different. In the multivariate analysis, SIBO (P=0.005) and the presence of a metabolic syndrome (P=0.006) were independent factors of severe hepatic steatosis. Conclusion In morbidly obese patients, bacterial overgrowth prevalence is higher than in healthy subjects and is associated with severe hepatic steatosis.