Quantitative CT assessment of psoas muscle index for predicting postoperative morbidity and mortality in major abdominal surgery

Abstract Background Sarcopenia—loss of skeletal muscle mass and function—has been linked to increased surgical morbidity and mortality. Computed tomography (CT)–derived psoas muscle index (PMI) offers an objective, opportunistic method for sarcopenia assessment, yet evidence in mixed surgical populations is limited. Objective To assess whether preoperative CT-derived PMI at L3 predicts major postoperative complications, intensive care unit (ICU) admission, and 30-day mortality in patients undergoing major elective surgery. Methods In this prospective observational study, 89 adult patients scheduled for major elective abdominal procedures between January 2022 and December 2023 underwent preoperative CT. Bilateral psoas cross-sectional area at L3 was measured and normalized to height (reported as cm 2 /m 2 ) to calculate PMI. Sarcopenia was defined using sex-specific PMI cutoffs (men < 6.36 cm 2 /m 2 ; women < 3.92 cm 2 /m 2 ). Postoperative complications were classified by Clavien–Dindo; grade ≥ III was considered major. Multivariable logistic regression adjusted for age, sex, BMI, and comorbidities. Interobserver agreement for psoas area was assessed by ICC. A two-tailed p < 0.05 denoted statistical significance. Results Among 89 patients, sarcopenia was present in 34 (38.2%). Sarcopenic patients had higher rates of major postoperative complications (35.3% versus 10.9%; p = 0.006), higher ICU admission (55.9% versus 20.0%; p = 0.001), and longer median hospital stay (10 days [IQR 8–14] versus 7 days [IQR 6–9]; p = 0.002). Thirty-day mortality was greater in the sarcopenic group (17.6% versus 5.5%) but did not reach statistical significance ( p = 0.062). On multivariable analysis adjusted for age, sex, BMI, and comorbidities, sarcopenia independently predicted major complications (OR 3.12; 95% CI 1.28–7.59; p = 0.012) and ICU admission (OR 2.94; 95% CI 1.05–8.25; p = 0.041). Conclusions Preoperative CT-derived PMI is an independent predictor of major complications and ICU admission after major elective surgery. Incorporating PMI measurement into preoperative evaluation may guide targeted optimization strategies.