Abdominal Wall Thickness Predicts Surgical Site Infection in Emergency Colon Operations

Abstract

Background: Body mass index (BMI) does not reliably predict Surgical site infections (SSI). We hypothesize that abdominal wall thickness (AWT) would serve as a better predictor of SSI for patients undergoing emergency colon operations. Methods: We retrospectively evaluated our Emergency Surgery Database (2007-2018). Emergency colon operations for any indication were included. AWT was measured by pre-operative CT scans at 5 locations. Only superficial and deep SSIs were considered as SSI in the analysis. Univariate then multivariable analyses were used to determine predictors of SSI. Results: 236 patients met inclusion criteria. The incidence of post-operative SSI was 25.8% and the median BMI was 25.8kg/m2 [22.5-30.1]. The median AWT between patients with and without SSI was significantly different (2.1cm [1.4, 2.8] and 1.8cm [1.2, 2.5], respectively). A higher BMI trended toward increased rates of SSI, but this was not statistically significant. In overweight (BMI 25-29.9kg/m2) and obese (BMI ≥30kg/m2) patients, SSI versus no SSI rates were (50.0% versus 41.9% and 47.4% versus 36.4%, P = 0.365 and 0.230) respectively. The incidence of SSI in patients with an average AWT < 1.8cm was 20% and 30% for patients with average AWT ≥1.8cm. On multivariable analysis, AWT ≥1.8cm at 2cm inferior to umbilicus was an independent predictor of SSI (OR 2.98, 95%CI 1.34-6.63, P = 0.007). Conclusions: AWT is a better predictor of SSI than BMI. Preoperative imaging of AWT may direct intraoperative decisions regarding wound management. Future clinical outcomes research in emergency surgery should include abdominal wall thickness as an important patient variable.