As most COVID-19 patients only receive thoracic CT scans, but body composition, which is relevant to detect sarcopenia, is determined in abdominal scans, this study aimed to investigate the relationship between thoracic and abdominal CT body composition parameters in a cohort of COVID-19 patients. This retrospective study included n = 46 SARS-CoV-2-positive patients who received CT scans of the thorax and abdomen due to severe disease progression. The subcutaneous fat area (SF), the skeletal muscle area (SMA), and the muscle radiodensity attenuation (MRA) were measured at the level of the twelfth thoracic (T12) and the third lumbar (L3) vertebra. Necessity of invasive mechanical ventilation (IMV), length of stay, or time to death (TTD) were noted. For statistics correlation, multivariable linear, logistic, and Cox regression analyses were employed. Correlation was excellent for the SF (r = 0.96) between T12 and L3, and good for the respective SMA (r = 0.80) and MRA (r = 0.82) values. With adjustment (adj.) for sex, age, and body-mass-index the variability of SF (adj. r2 = 0.93; adj. mean difference = 1.24 [95% confidence interval (95% CI) 1.02–1.45]), of the SMA (adj. r2 = 0.76; 2.59 [95% CI 1.92–3.26]), and of the MRA (adj. r2 = 0.67; 0.67 [95% CI 0.45–0.88]) at L3 was well explained by the respective values at T12. There was no relevant influence of the SF, MRA, or SMA on the clinical outcome. If only thoracic CT scans are available, CT body composition values at T12 can be used to predict abdominal fat and muscle parameters, by which sarcopenia and obesity can be assessed.

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 ^ ORCID: Isabel Molwitz, 0000-0003-4542-0140; Marius Kemper, 0000-0003-4831-8782.superior to cut-off-based systems in predicting the outcome after major hepatic surgery.