Importance of computed tomography muscle quality and continuous versus cut-off-based sarcopenia detection in major hepatic surgery

Background: The role of the computed tomography (CT)-derived skeletal muscle index (SMI) as a parameter of muscle quantity on the outcome after major liver resection remains contradictory and that of the muscle radiodensity attenuation (MRA) as a parameter of muscle quality has not been sufficiently evaluated. This observational study aimed to investigate the influence of metric SMI and MRA values and cut-off-based CT sarcopenia detection on liver-surgery specific complications measured by the new FABIB (liver failure, ascites, biliary leakage, infection, bleeding) score and survival after hemihepatectomy.

Methods: A total of 183 patients with major hepatectomy were retrospectively included. The SMI and MRA were determined from the abdominal muscle area of preoperative CT scans. Patients were classified as sarcopenic by the SMI and MRA cut-off values of Prado et al., Martin et al., and van der Werf et al. Postoperative complications were documented according to the Clavien-Dindo classification and FABIB score. The relation of the continuous, non-categoric SMI and MRA values and of the cut-off-based sarcopenia detection to the postoperative complications and survival was analyzed by multivariable linear, logistic, and Cox proportional hazards regression.

Results: A higher MRA was associated with less severe postoperative complications in the Clavien-Dindo [-0.59 (95% CI: -0.95 to -0.23), P=0.002] and the FABIB score [-0.65 (95% CI: -1.19 to -0.12), P=0.017]. An increase of the SMI did not result in less severe complications in the Clavien-Dindo [0.14 (95% CI: -0.27 to 0.55), P=0.503] or FABIB score [0.17 (95% CI: -0.42 to 0.76), P=0.572]. For patients classified as sarcopenic by the cut-off-based systems no relevant relation to postoperative complications was found. Overall survival was better for a higher MRA [hazard ratio (HR): 0.75 (95% CI: 0.58-0.97), P=0.029], as long-term survival was for a higher SMI [HR: 0.68 (95% CI: 0.47-0.96), P=0.031]. Only below van der Werf's MRA cut-off the probability of overall and long-term survival was reduced [HR: 2.32 (95% CI: 1.18-4.54), P=0.015; 2.68 (95% CI: 1.25-5.74), P=0.011].

Conclusions: The MRA has a stronger influence on complications in the Clavien-Dindo classification and the liver-surgery specific FABIB score than the SMI. Continuous, non-categoric MRA and SMI values are superior to cut-off-based systems in predicting the outcome after major hepatic surgery.