Objectives: To measure the effect of obesity on surgical site infection (SSI) rates and to define the cost of SSIs in patients undergoing colorectal surgery. Design, Setting, and Patients: This is a retrospective cohort study of 7020 colectomy patients using administrative claims data from 8 Blue Cross and Blue Shield insurance plans. Patients who had a total or segmental colectomy for colon cancer, diverticulitis, or inflammatory bowel disease between January 1, 2002, and December 31, 2008, were included. Main Outcome Measures: We compared 30-day SSI rates among obese and nonobese patients and calculated total costs from all health care claims for 90 days following surgery. Multivariate logistic regression was performed to identify risk factors for SSIs. Results: Obese patients had an increased rate of SSI compared with nonobese patients (14.5% vs 9.5%, respectively; P<.001). Independent risk factors for these infections were obesity (odds ratio=1.59; 95% confidence interval, 1.32-1.91) and open operation as compared with a laparoscopic procedure (odds ratio=1.57; 95% confidence interval, 1.25-1.97). The mean total cost was $31 933 in patients with infection vs $14 608 in patients without infection (P<.001). Total length of stay was longer in patients with infection than in those without infection (mean, 9.5 vs 8.1 days, respectively; P<.001), as was the probability of hospital readmission (27.8% vs 6.8%, respectively; P<.001). Conclusions: Obesity increases the risk of an SSI after colectomy by 60%, and the presence of infection increases the colectomy cost by a mean of $17 324. Pay-for-performance policies that do not account for this increased rate of SSI and cost of caring for obese patients may lead to perverse incentives that could penalize surgeons who care for this population.
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