Published online Feb 7, 2017. doi: 10.3748/wjg.v23.i5.842
Peer-review started: August 28, 2016
First decision: October 20, 2016
Revised: October 22, 2016
Accepted: November 16, 2016
Article in press: November 16, 2016
Published online: February 7, 2017
To identify a set of contributors, and weight and rank them on a pathophysiological basis.
Patients who have undergone a lactulose or glucose hydrogen breath test to rule out small intestinal bacterial overgrowth (SIBO) for various clinical symptoms, including diarrhoea, weight loss, abdominal pain, cramping or bloating, were seen as eligible for inclusion in a retrospective single-centre study. Clinical data such as co-morbidities, medication, laboratory parameters and other possible risk factors have been identified from the electronic data system. Cases lacking or with substantially incomplete clinical data were excluded from the analysis. Suspected contributors were summarised under four different pathophysiological pathways (impaired gastric acid barrier, impaired intestinal clearance, immunosuppression and miscellaneous factors including thyroid gland variables) and investigated using the χ2 test, Student’s t-test and logistic regression models.
A total of 1809 patients who had undergone hydrogen breath testing were analysed. Impairment of the gastric acid barrier (gastrectomy, odds ratio: OR = 3.5, PPI therapy OR = 1.4), impairment of intestinal clearance (any resecting gastric surgery OR = 2.6, any colonic resection OR = 1.9, stenosis OR = 3.4, gastroparesis OR = 3.4, neuropathy 2.2), immunological factors (any drug-induced immunosuppression OR = 1.8), altered thyroid gland metabolism (hypothyroidism OR = 2.6, levothyroxine therapy OR = 3.0) and diabetes mellitus (OR = 1.9) were associated significantly to SIBO. Any abdominal surgery, ileocecal resection, vagotomy or IgA-deficiency did not have any influence, and a history of appendectomy decreased the risk of SIBO. Multivariate analysis revealed gastric surgery, stenoses, medical immunosuppression and levothyroxine to be the strongest predictors. Levothyroxine therapy was the strongest contributor in a simplified model (OR = 3.0).
The most important contributors for the development of SIBO in ascending order are immunosuppression, impairment of intestinal clearance and levothyroxine use, but they do not sufficiently explain its emergence.
Core tip: Several contributors to small intestinal overgrowth have been described, but the impact of particular risk factors is poorly understood. We aimed to determine the influence of several pathomechanisms, such as impaired gastric acid barrier function, impaired intestinal clearance, impairment of defence mechanisms and miscellaneous factors, as well as to weight and rank a large set of potential contributors by means of a retrospective cohort study of 1809 consecutive patients who had undergone a hydrogen breath test to rule out small intestinal bacterial overgrowth. Overall, levothyroxine therapy, impaired intestinal clearance and immunosuppression are the strongest contributors, while an impaired gastric acid barrier only plays a minor role.