Introduction Small intestinal bacterial overgrowth (SIBO) testing is confounded by transit time, which can be increased in a number of surgical conditions. This study aims to evaluate whether patients who have undergone a gastric bypass, small bowel resection or who have been diagnosed with short bowel syndrome have a higher prevalence of SIBO than patients who have not, and whether they respond to antibiotic treatment

Methods In total, 520 adult patients (360 female, 160 male, mean age 49) who underwent hydrogen and glycocholate-methane breath tests for a suspicion of SIBO between the dates 01/01/2010 and 31/12/2013 were evaluated. Their clinical information including their test results, working diagnosis, management and outcomes of management were recorded.

Results 84 patients had undergone a gastric bypass (31), small bowel resection (27) or had been diagnosed with short bowel syndrome (26). 40 of these patients tested positive in both hydrogen and glycocholate-methane breath tests (48.2%). 437 patients with normal anatomy were also tested over the same period, of which 61 tested positive (14.0%). (48.2% vs 14.0%, Chi-square statistic = 50.8911, p = 0). 34 patients who had undergone a gastric bypass, small bowel resection or had been diagnosed with short bowel syndrome who tested positive were treated with antibiotics. 28 (82.4%) benefitted from this. 56 patients who tested positive in the other group were given antibiotics, 41 (73.2%) of whom benefitted from this.

Conclusion Patients who had undergone a gastric bypass, small bowel resection or have been diagnosed with short bowel syndrome have a much higher rate of positive SIBO test results compared to patients who have not, and have a similar response rate to antibiotic therapy. This suggests these post-surgical patients have a higher incidence of true SIBO than those with normal anatomy and benefit from antibiotics. This implies these are true positive cases and not false positives due to shortened transit times. Future studies controlling for transit would help clarify these findings further.

Disclosure of Interest None Declared