Muscle Ultrasound for Sarcopenia Assessment in Kidney Transplant Recipients (KT-SARC)

Sarcopenia is highly prevalent among patients with end-stage renal disease and is associated with poor clinical outcomes. Although kidney transplantation may improve overall health status, perioperative stress, immunosuppressive therapy, and postoperative metabolic changes may influence muscle mass and function. Reliable assessment of sarcopenia in kidney transplant recipients remains clinically important.

Current methods for sarcopenia assessment include computed tomography (CT), dual-energy X-ray absorptiometry (DXA), and bioelectrical impedance analysis (BIA). However, CT and DXA are limited by radiation exposure, cost, and accessibility, while BIA may be affected by changes in hydration status, especially in transplant recipients. Muscle ultrasound is a portable, radiation-free, and bedside-available imaging modality that may provide a practical alternative for muscle assessment.

This prospective observational study will enroll adult kidney transplant recipients at Sichuan Provincial People's Hospital. Participants will undergo multimodal muscle ultrasound and BIA examinations at predefined perioperative time points. Ultrasound parameters will include muscle thickness, cross-sectional area, and echogenicity.

The primary study objective is to evaluate the diagnostic performance of muscle ultrasound for sarcopenia assessment using BIA-derived skeletal muscle index (BIA-SMI) as the reference standard. Correlation analysis, intraclass correlation coefficients, Bland-Altman analysis, and receiver operating characteristic (ROC) curve analysis will be performed to evaluate agreement and diagnostic accuracy.

Secondary objectives include evaluating longitudinal changes in muscle-related parameters and sarcopenia prevalence from the pre-transplant period to 1 year after kidney transplantation. Linear mixed-effects models or generalized estimating equations will be used to analyze temporal trends.

This study aims to establish muscle ultrasound as a practical and reliable tool for sarcopenia assessment in kidney transplant recipients and to improve understanding of perioperative muscle changes after transplantation.