Consequences of Small Intestinal Bacterial Overgrowth in Obese Patients Before and After Bariatric Surgery.

Background and Aims: Small intestinal bacterial overgrowth (SIBO) has been described in obese patients. The aim of this study was to prospectively evaluate the prevalence and consequences of SIBO in obese patients before and after bariatric surgery.
Patients and Methods: From October 2001 to July 2009, in obese patients referred for bariatric surgery (BMI >40 kg/m ² or >35 in association with comorbidities), a glucose hydrogen (H ₂ ) breath test (BT) was performed before and/or after either Roux-en-Y gastric bypass (RYGBP) or adjustable gastric banding (AGB) to assess the presence of SIBO. Weight loss and serum vitamin concentrations were measured after bariatric surgery while a multivitamin supplement was systematically given.
Results: Three hundred seventy-eight (mean ± SD) patients who performed a BT before and/or after surgery were included: before surgery, BT was positive in 15.4 % (55/357). After surgery, BT was positive in 10 % (2/20) of AGB and 40 % (26/65) of RYGBP (p < 0.001 compared to preoperative situation). After RYGBP, patients with positive BT had similar vitamin levels, a lower caloric intake (983 ± 337 vs. 1271 ± 404 kcal/day, p = 0.014) but a significant lower weight loss (29.7 ± 5.6 vs. 37.7 ± 12.9 kg, p = 0.002) and lower percent of total weight loss (25.6 ± 6.0 vs. 29.2 ± 6.9 %, p = 0.044).
Conclusion: In this study, SIBO is present in 15 % of obese patients before bariatric surgery. This prevalence does not increase after AGB while it rises up to 40 % of patients after RYGBP and it is associated with lower weight loss.