A Retrospective Study of Small Intestinal Bacterial Overgrowth in Patients with Bloating

Abstract

Purpose: Many patients (80–90%) with IBS consider bloating their most bothersome symptom. Recent studies suggest a link between abdominal bloating and/or irritable bowel syndrome (IBS) and small intestinal bacterial overgrowth (SIBO). The prevalence of SIBO in patients with bloating, with or without IBS, is unknown. We determined the prevalence of SIBO in patients referred for lactulose breath test (LBT) and response to treatment for SIBO in patients with bloating. Methods: Selection criteria for enrollment included; >18 years of age and LBT with bloating as a symptom at the UUHSC from Jan 2004 to May 2007. A chart review was performed to collect information including; indication for LBT, LBT results, presence or absence of IBS and treatment and response. SIBO was diagnosed by LBT. An LBT positive result was defined as an early rise (<90 min) in hydrogen (>20 ppm) or methane (>12 ppm). IBS was diagnosed clinically. A positive response was defined as moderate or greater improvement by patient or physician subjective criteria. Chi square or Fisher's exact test were used to make comparisons between groups. Results: A total of 255 breath tests were performed. There were 169 patients with bloating as a symptom (9 with no result). The mean age for patients with bloating was 47.6 years ± 15.8, 69% were female. The prevalence of positive SIBO in patients with bloating was 51% (82/160). The prevalence of positive SIBO was different between patients referred for bloating vs. referred for other reasons ((82/160 (51%) vs. 27/86 (31%), P= 0.004)). The prevalence of positive SIBO in patients with bloating and IBS was 22/42 (52%). There was no difference in the prevalence of SIBO in patients with and without IBS ((22/42 (52%) versus 62/118 (46%) P= NS)). 82% (28/34) of patients with bloating and positive LBT responded to antibiotic treatment vs. 33% (3/9) of patients with bloating and negative LBT (P= 0.008, OR = 9.3). Patients were followed for 10.4 ± 7.7 months for response. Conclusion: In patients with bloating referred for LBT, SIBO positivity was significantly higher than in patients referred for other reasons. In patients with bloating, SIBO positivity was not different in patients with and without IBS. Patients with bloating and positive SIBO by LBT are significantly more likely to respond to antibiotic Rx than patients with bloating and negative SIBO by LBT. Further investigation of factors associated with bloating, SIBO and response to antibiotic therapy is warranted.