Skeletal Muscle Density as an Independent Predictor of Prolonged Postoperative Hospital Stay After Surgery for Acute Cholecystitis

Background/Objectives: Prolonged postoperative length of stay (LOS) is associated with increased morbidity and healthcare utilization following surgery for acute cholecystitis. The prognostic value of skeletal muscle density (SMD), a marker of muscle quality, is unclear. We aimed to evaluate the association between SMD and prolonged LOS and to compare the predictive performance of SMD with that of skeletal muscle index (SMI). Methods: A retrospective study of 382 patients who underwent surgery for acute cholecystitis was conducted. LOS was defined using mean- and median-based cut-offs. Multivariate logistic regression was used to identify independent predictors. Model performance was assessed using the area under the receiver operating characteristic curve (AUC) and Akaike information criterion (AIC). Robustness was assessed using count-based modeling, spline analysis, and model calibration. Results: Patients with prolonged LOS were older, had lower body mass index and serum albumin levels, higher inflammatory markers, and more comorbidities, and had significantly lower SMD. Higher SMD was independently associated with a reduced risk of prolonged LOS (adjusted OR per 1-HU increase, 0.93; 95% CI, 0.88–0.97; p = 0.002). The SMD-based model showed acceptable discrimination (AUC 0.78) and slightly better model fit than the SMI-based model (AIC 365.1 vs. 371.2). In secondary analyses, patients in the lowest SMD quartile had significantly higher postoperative complication rates than the remaining patients (10.5% vs. 2.8%; p = 0.004). Conclusions: Overall, lower SMD was independently associated with prolonged LOS after surgery for acute cholecystitis and may serve as a readily available imaging biomarker for perioperative risk stratification.