Incidence and risk of venous thromboembolism in patients following appendectomy: a nationwide cohort study.

Surgery may lead to poor blood flow and hypercoagulation. Few studies have investigated the incidence of venous thromboembolism (VTE) in Asian patients following appendectomy. We conducted a nationwide cohort study to investigate the risk of VTE in patients who underwent appendectomy compared with those who did not in Taiwan. We studied the entire hospitalized population in Taiwan from 2000 to 2012, with a follow-up period extending to the end of 2013. We identified patients who underwent appendectomy in Taiwan's National Health Insurance Research Database as the appendectomy cohort, and selected a nonappendectomy cohort from the general population that was 4:1 frequency-matched by age (5-year interval), sex, and index year for each appendectomy case. We used Cox models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for symptomatic VTE in the appendectomy cohort for comparison with the nonappendectomy cohort. The appendectomy cohort exhibited a higher incidence of symptomatic VTE than the nonappendectomy cohort (5.90 vs. 3.29 per 10,000 person-years). After adjustment for covariates, a 1.68-fold HR for symptomatic VTE was observed in the appendectomy cohort (95% CI 1.56-1.81). Compared with the nonappendectomy cohort, the patients who underwent open appendectomy had a 1.73-fold increased adjusted HR for symptomatic VTE (95% CI 1.61-1.87). Laparoscopic appendectomy was not significantly associated with symptomatic VTE. An 8.15-fold higher adjusted HR for VTE was observed in patients who underwent appendectomy within the first month after surgery compared with the nonappendectomy cohort. Open appendectomy carried an increased risk of symptomatic VTE. Laparoscopic appendectomy was not significantly associated with symptomatic VTE.