Urinary tract infection after colon and rectal resections: more common than predicted by risk-adjustment models

Abstract

Background: Urinary tract infections (UTIs) are the most common hospital-acquired infections in the United States. We hypothesized that the risk of UTI after colorectal surgery exceeds the risk after other gastrointestinal operations.

Study design: We used National Surgical Quality Improvement Program (NSQIP) data from 2005 to 2008 to compute rates of UTI after colorectal resections and other gastrointestinal and general surgery. We used a validated multivariate UTI prediction model to compare risk-adjusted rates of UTI by type of procedure. Then we identified predictors of UTI after colorectal resection using stepwise logistic regression models.

Results: Crude UTI rates were significantly greater after colorectal resection (4.1%) than after other gastrointestinal (1.8%) or nongastrointestinal procedures (1.2%; all p < 0.001). Even using standard risk-adjustment from the NSQIP, rates of UTI were significantly higher after segmental colectomy (2.8%; 95% CI 2.5% to 3.2%), total colectomy (3.5%; 95% CI 2.9% to 4.3%), proctectomy (3.5%, 95% CI 3.1% to 4.2%), proctocolectomy (4.6%, 95% CI 3.8% to 5.7%), and abdominoperineal resection (5.6%, 95% CI 4.6% to 6.8%) than after noncolorectal gastrointestinal surgery (2.6%, 95% CI 2.2% to 2.9%). Factors associated with UTI after colorectal resections include age, sex, functional status, American Society of Anesthesiologists class, and resection type.

Conclusions: Colorectal resections incur substantial risk of postoperative UTI, exceeding rates predicted by the NSQIP model. Because of their patients' unanticipated high incidence of UTI, surgeons with a specialty interest in colorectal surgery risk being flagged as "high outliers," particularly if they perform many rectal resections. A simple set of risk factors discriminates 10-fold differences in the rate of UTI after colorectal resection.