Beyond BMI: Using Abdominal Wall Thickness to Guide Patient Selection for DIEP Flap Breast Reconstruction

Introduction: BMI limits of 30.0 to 32.7 kg/m2 have been recommended to reduce post-operative complications in autologous breast reconstruction. However, BMI does not accurately represent body composition for all individuals. This study evaluates the relationship between abdominal wall thickness (AWT) and post-operative complication rates using a novel, accessible measuring method. Methods: A retrospective chart review of 793 patients (1310 flaps) who underwent DIEP flap reconstruction from November 2017 to May 2024 at two medical institutions was conducted. Demographics, medical history, operative course, and post-operative complications were reviewed. Subcutaneous AWT was measured on pre-operative CT angiogram at four standardized anatomical landmarks. Patients were stratified by BMI (<25, 25–30, 30–35, and >35) and AWT (<20 mm, 20–40 mm, and >40 mm). Statistical analysis was conducted in R. Results: The mean patient age was 50.5 years, and mean BMI was 30.3 kg/m2. BMI was strongly correlated with AWT (r = 0.68, p < 0.001), and both variables were strong predictors for complication rates (p < 0.001, p < 0.001). Stepwise increases in wound dehiscence, infection, and fat necrosis were observed across AWT groups. ROC analysis identified AWT threshold of 26.3 mm for overall complications. AWT and BMI models demonstrated comparable predictive ability for complication rates. Patients with mismatched BMI and AWT highlighted cases where BMI alone underestimated risk. Conclusion: Abdominal wall thickness may serve as a valuable adjunct tool in determining DIEP flap eligibility, particularly for patients with a high BMI and thin abdominal wall, or vice versa.