Thigh muscle index as a valuable prognostic marker in middle-aged male patients undergoing liver transplantation.

In liver transplantation (LT), determining the optimal recipients is crucial, and the MELD score has been used for this purpose. However, the MELD score does not reflect functional status, leading to the evaluation of sarcopenia. While the L3 skeletal muscle index (SMI L3 ) is commonly used for assessment, the upper thigh skeletal muscle index (SMI UT ) may better represent functional capacity. This retrospective study included 246 male LT recipients aged 40-60 from 2013 to 2015. Preoperative and postoperative muscle and fat areas at the L3 and upper thigh levels were quantified using artificial intelligence software. Clinical outcomes, including ventilator, intensive care unit, and hospital days, were analyzed using logistic regression, while survival was evaluated using Cox regression and Kaplan-Meier curves. Longitudinal body composition changes were assessed over 5 years post-LT. SMI UT demonstrated stronger associations with hospital days ( R2 =0.378) than SMI L3 ( R2 =0.302). High SMI UT correlated with improved survival ( p =0.02), unlike SMI L3 . Longitudinal analysis revealed a significant divergence in SMI UT between survivors and non-survivors, whereas SMI L3 showed no significant changes. The visceral fat index at L3 (VFI L3 ) increased continuously, highlighting potential metabolic risks. SMI UT showed a similar or even stronger association with LT outcomes than SMI L3 , effectively reflecting patient prognosis. SMI UT in the postoperative period also better reflected clinical status. Therefore, preoperative and postoperative SMI UT is helpful for patient assessment and ongoing management in LT patients.