OBJECTIVES: Prediction of intra-abdominal infection (IAI) in patients with abdominal trauma is crucial, yet reliable predictive indicators are currently lacking. The sarcopenia index (SI) is a readily available indicator of clinical outcomes in several diseases that holds diagnostic and prognostic value. The aim of this study is to assess the predictive value of SI for IAI in patients with abdominal trauma. METHODS: This retrospective cohort study enrolled patients with abdominal trauma. Multivariable logistic analyses were used to identify independent factors of IAI. We divided patients into 2 groups based on sex. The receiver operating characteristic (ROC) curve was used to evaluate the performance of SI in predicting IAI. Then, based on the cut-off values of the SI established for males and females, we stratified patients into high and low-IAI risk groups to compare clinical outcomes. Spearman correlation analysis was used for correlation analysis. RESULTS: A total of 378 participants with abdominal trauma were included. Multivariable logistic analyses identified SI as an independent risk factor for IAI in both males [odds ratio (OR): 0.82, 95% confidence interval (CI): 0.74-0.90, P <
0.001] and females (OR: 0.68, 95% CI: 0.51-0.91, P = 0.009). The area under the ROC curve for SI in predicting IAI was 0.712 for males and 0.733 for females, with optimal cut-off values of 81.430 for males and 57.907 for females. Furthermore, SI showed significant correlations with the length of hospital stay (P = 0.003) and hospital costs (P = 0.042). CONCLUSIONS: SI was identified as an independent risk factor for IAI in patients with abdominal trauma, offering predictive value for both genders. SI correlates with poor clinical outcomes. This might provide new ideas and theoretical guidance for diagnosing and treating IAI.