Background and study aims Previous studies describingthe incidence of infection after colonoscopy and sigmoidoscopyare limited. The aim of this study was to determinethe incidence of infection, and to propose a nomogram topredict the probability of infection following colonoscopyand sigmoidoscopy in symptomatic patients.
Patients and methods A nationwide retrospective studywas conducted by analyzing the National Health Insurance
Research Database of Taiwan. The incidence of infectionwithin 30 days after colonoscopy and sigmoidoscopy was
assessed and compared with a control group matched at aratio of 1:1 based on age, sex, and the date of examination.
Results In all, 112 543 patients who underwent colonoscopyor sigmoidoscopy and 112 543 matched patients who
did not undergo these procedures were included. The overallincidence of infection within 30 days after colonoscopy
and sigmoidoscopy was 0.37%, which was significantlyhigher than that of the control group (0.04%; P < 0.001). Diverticulitis,peritonitis, and appendicitis were the mostcommon infections. Patients who underwent colonoscopy
or sigmoidoscopy had a 9.38-fold risk of infection (95%confidence interval, 6.81 – 12.93; P < 0.001) compared with
the control group. The predicted infection-free rates of thenomogram were closely aligned with the actual infectionfree
rates, with a bootstrapping concordance index of0.763.Conclusions Colonoscopy and sigmoidoscopy are associated
with an increased risk of infection, which may occurafter these procedures. Our nomogram may provide clinicianswith an easy tool to evaluate the risk of infection aftercolonoscopy and sigmoidoscopy in symptomatic patients.
