Incidence of venous thromboembolism after bariatric surgery: a population-based cohort study.

Background: The incidence of venous thromboembolism (VTE) after bariatric surgery is uncertain.
Methods: Using the resources of the Rochester Epidemiology Project and the Mayo Bariatric Surgery Registry, we identified all residents of Olmsted County, Minnesota, with incident VTE after undergoing bariatric surgery from 1987 through 2005. Using the dates of bariatric surgery and VTE events, we determined the cumulative incidence of VTE after bariatric surgery by using the Kaplan–Meier estimator. Cox proportional hazards modeling was used to assess patient age, sex, weight, and body mass index as potential predictors of VTE after bariatric surgery.
Results: We identified 396 residents who underwent 402 bariatric operations. The most common operation was an open Roux-en-Y gastric bypass (n =228). Eight patients had VTE that developed within 6 months (7 within 1month) after surgery; five events occurred after hospital discharge but within 1 month after bariatric surgery. The cumulative incidence of VTE at 7, 30, 90, and 180 days was 0.3, 1.9, 2.1, and 2.1%, respectively (180-day 95% confidence interval (CI), 0.7–3.6%). Patient age was a predictor of postoperative VTE (hazard ratio, 1.89 per 10-year increase in age; 95% CI, 1.01–3.55; P=0.05).
Conclusions: In our population-based study, bariatric surgery had a high risk of VTE, especially for older patients. Because most VTE events occurred after hospital discharge, a randomized controlled trial of extended outpatient thromboprophylaxis is warranted in patients undergoing open Roux-en-Y gastric bypass for medically complicated obesity.