Abstract

The obesity paradox has been described in blunt trauma, where adiposity may attenuate energy transfer and reduce injury severity. Whether this applies to clinically relevant penetrating abdominal trauma remains unclear. To evaluate whether obesity, defined by body mass index, is associated with reduced intra-abdominal organ injury in adults with clinically relevant penetrating abdominal trauma. This retrospective cohort study included adults presenting with clinically relevant penetrating abdominal trauma at a tertiary trauma centre between January 1, 2020, and December 31, 2025. Of 710 screened patients, 25 with isolated superficial injuries, 35 with inaccessible records, and 100 with missing body mass index (BMI) data were excluded; 550 patients were analyzed. The primary outcome was intra-abdominal organ injury. Multivariate penalized logistic regression assessed the association between obesity and injury occurrence, adjusting for injury mechanism, hemodynamic status, and other clinically available covariates. Mechanism-stratified analyses and ROC analysis of BMI were also performed. Among 550 patients, 339 (61.6%) sustained intra-abdominal organ injury. Obesity was not independently associated with organ injury after adjustment (adjusted OR, 1.33; 95% CI, 0.75–2.34). In mechanism-stratified analyses, obesity was not associated with organ injury in stab wounds, whereas the firearm subgroup showed wide confidence intervals. No BMI–mechanism interaction was observed. BMI showed poor discrimination for any organ injury (AUC ≈0.51), with similarly limited performance for solid and hollow viscus injuries. In patients with clinically relevant penetrating abdominal trauma, obesity did not confer visceral protection and BMI had no meaningful predictive value for injury risk. Because isolated superficial injuries were excluded, these findings do not exclude a possible effect of adiposity on fascial penetration. They suggest that, once clinically relevant penetrating trauma is present, the obesity paradox described in blunt trauma does not extend to penetrating mechanisms and should not influence clinical risk assessment.

Key words: Penetrating abdominal trauma, obesity, body mass index, organ injury, trauma surgery, obesity paradox