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LAS VEGAS -- Weeks after undergoing Roux-en-Y gastric bypass surgery, U.S. patients showed increased risk for Clostridium difficile infections compared with patients who underwent other abdominal surgeries in a nationwide study, a researcher reported here.

The adjusted odds ratio for readmission with a C. difficile infection from 31 to 120 days after post-bypass discharge was 9.8 relative to vertical sleeve gastrectomy (95% CI 1.2-77.0), among patients included in the Nationwide Readmissions Database for 2013, reported , of Ohio State University in Columbus.

And compared with patients undergoing ventral hernia repair, the risk of C. difficile-related readmission at 31-120 days following gastric bypass was similarly increased (adjusted OR 6.67, 95% CI 1.75-25.4), he told attendees at the .

Although the study design did not permit firm conclusions about causality, Ugbarugba speculated that the reduction in stomach acid secretion following gastric bypass was responsible for the increased C. difficile infection risk, presumably because it would create an environment more favorable to the organism.

Session moderator of the Icahn School of Medicine at Mt. Sinai in New York City, who had invited Ugbarugba to offer a mechanistic explanation, called it "plausible" but added that it would need testing. Ugbarugba agreed, saying that "multiple factors" could play a role in such an effect.

The Nationwide Readmissions Database was launched earlier this year by the Agency for Healthcare Research and Quality with data restricted thus far to calendar year 2013. It includes data obtained from 21 state-level repositories, covering about half of all U.S. hospitalizations. Data are based on ICD-9 codes; Ugbarugba noted that, for C. difficile infection, only those cases where the condition was listed as the primary reason for readmission were counted in the analysis.

To capture up to 120 days of follow-up after initial discharge, Ugbarugba and colleagues analyzed inpatient surgeries for Roux-en-Y bypass performed from January through August of 2013. Exclusion criteria included pregnancy, previous bariatric surgery, age under 18, and bypass surgery performed for cancer rather than for metabolic indications. A total of 40,191 bypass surgery patients were included in the analysis. The two comparator groups were patients undergoing sleeve gastrectomy (n=45,644) and obese individuals undergoing ventral hernia repair (n-10,995).

Absolute rates of readmission for C. difficile infection remained low in the bypass patients, Ugbarugba noted -- less than 0.2% overall, with 70 patients readmitted for the infection during the 4-month follow-up period. However, he showed a Kaplan-Meier curve showing that, while C. difficile readmissions after sleeve gastrectomy topped out within the first month, they continued to climb throughout follow-up in the gastric bypass patients, suggesting an ongoing risk.

Ugbarugba noted several limitations: the reliance on administrative data including ICD-9 codes, inability to identify the source of C. difficile infections during follow-up, and lack of data on potential confounders such as proton pump inhibitor use.

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