Psoas muscle mass index as a predictor of long-term mortality and severity of complications after major intra-abdominal colorectal surgery – A retrospective analysis

Study objective: Determine if psoas muscle area measured in routine preoperative computed tomography scans (CT) can be used to identify patients at increased risk of adverse postoperative outcomes after major elective abdominal surgery. Design: Retrospective analysis of data from a single-centre cohort study conducted in York Hospital between the 1st August of 2015 and the 31st of august of 2020. Setting: Preoperative clinic. Patients: 639 patients who attended the preoperative assessment clinic prior to major elective colorectal surgery and had an abdominal CT scan done up to 120 days before surgery. Interventions: None. Measurements: Psoas muscle area at the L3 level was measured in preoperative CT scans and normalised to patient height (psoas muscle index). The lowest sex-stratified tertile of psoas muscle index (PMI) was classed as sarcopenic. The primary outcome was 2-year mortality. Secondary outcomes included postoperative complications assessed using Clavien-Dindo graded major and minor complications, comprehensive complication index (CCI), and length of stay. Main results: Multivariable regression analysis showed that sarcopenia was associated with 2-year mortality (aOR 1.79, 95% CI 1.03–3.10; p = 0.037) and survival at 2-years was significantly reduced in sarcopenic patients (log- rank test, p = 0.012). Sarcopenia was the only statistically significant predictor of major complications in multivariable logistic regression analysis (aOR 1.69, 95% CI 1.04–2.74, p = 0.034) and associated with an estimated increase of 16.6% in the comprehensive complication index (CCI) score of patients that had compli-cations in multivariable linear regression analysis. Sarcopenia was not associated with length of stay. Conclusions: Sarcopenia defined by psoas muscle mass is an independent predictor of 2-year mortality, major complications and severity of complications after major colorectal surgery and may be used for preoperative risk assessment.