Patients With Functional Dyspepsia May Be at Increased Risk for SIBO

SIBO, small intestine bacterial overgrowth medical 3D illustration
Investigators evaluated the prevalence of small intestinal bacterial overgrowth (SIBO) in a well-defined cohort of patients with functional dyspepsia (FD) using quantitative microbiological assessment of the duodenal aspirate.

In a cohort of patients with functional dyspepsia (FD), the prevalence of small intestinal bacterial overgrowth (SIBO) was found to approximate that of patients with irritable bowel syndrome (IBS), but was notably higher in the FD group than in the control group, according to findings from a study published in Digestive Diseases. SIBO incidence was also “significantly” elevated in the postprandial distress syndrome (PDS) and PDS- epigastric pain syndrome (EPS) FD subgroups, but not in the EPS subpopulation.

FD is a multifactorial disorder implicating several different pathophysiological mechanisms, and SIBO has been postulated to have a role in FD. However, data supporting this hypothesis are scarce and somewhat conflicting, therefore the researchers decided to investigate the prevalence of SIBO in a cohort of 227 patients who fulfilled Rome IV criteria for FD.

SIBO was defined as greater than or equal to 103 CFU/ml of duodenal aspirate and/or the presence of colonic type bacteria. The study authors used a quantitative microbiological assessment of the duodenal aspirate to facilitate the assessment.

Overall, SIBO prevalence was significantly higher in patients with FD (44/227 [19.4%]) compared with patients in the control group (1/30 [3.3%]; P =.037). However, SIBO incidence was similar in patients with FD and patients with IBS (44/227 [19.4%] vs 15/90 [16.7%]; P =.63). SIBO presence was not associated with the total or any subscale scores of the PAGI-SYM questionnaire for symptom severity.

“Our study showed that SIBO is more prevalent among FD patients, a finding suggesting that intestinal dysbiosis—manifesting as SIBO—could be associated with symptom generation or exacerbation in a subset of patients with FD,” the study authors wrote.

SIBO prevalence was also found to be higher in certain FD subtypes. Of the 227 patients with FD, 144 (63.4%), 64 (28.2%), and 19 (8.4%) had PDS, EPS, and overlap PDS-EPS syndrome, respectively. SIBO prevalence was higher in the overlap PDS-EPS subgroup (31.6%) compared with the PDS patient subgroup (20.8%; P =.21) and the EPS subpopulation (12.5%; P =.06), but the difference was not statistically significant. There was also no significant difference in SIBO prevalence between patients in the PDS and EPS groups (P =.18).

SIBO incidence was “significantly higher” in the overlap PDS-EPS subgroup vs the control group (31.6% vs 3.3%; P =.01). This trend continued in the PDS subgroup (20.8% vs 3.3%; P =.014).

Limitations to the study included its cross sectional status, which made establishing a definitive causal relationship difficult. The investigators also did not perform culture for anaerobic organisms or deep sequencing analysis, and the lack of breath-test analysis prevented confirmation of methane involvement in the pathogenesis of certain FD symptoms. The control group’s inclusion of patients with non-erosive reflux disease constituted the final limiting factor.

“Our study prospectively demonstrated for the first time using very strict definition criteria and duodenal aspirate culture that SIBO prevalence is higher among FD patients. Further data are warranted in this direction to better delineate a causal relationship,” the study authors concluded.


Tziatzios G, Gkolfakis P, Papanikolaou IS, et al. High prevalence of small intestinal bacterial overgrowth among functional dyspepsia patients. Dig Dis. Published online October 2, 2020. doi: 10.1159/000511944