Low Preoperative Exercise Tolerance Predicts Impaired Skeletal Muscle Recovery After Kidney Transplantation

Sarcopenia remains a significant concern among kidney transplant recipients even after renal function improves. However, the predictors of impaired muscle recovery are not well established.

We retrospectively analyzed 40 adults who underwent living-donor kidney transplantation at Kansai Medical University Hospital between January 2018 and December 2020. Preoperative cardiopulmonary exercise testing (CPX) was used to stratify patients into low-tolerance (anaerobic threshold VO₂ < 11 mL/kg/min and peak VO₂ < 20 mL/kg/min) and normal groups. The skeletal muscle index (SMI) was measured using dual-energy x-ray absorptiometry from baseline to 3 years post-transplantation. Multivariable linear regression and correlation analyses were performed to identify predictors of long-term SMI improvement.

Forty recipients were analyzed, including 12 (30%) in the low-tolerance group. Following transplantation, the median SMI in both groups decreased at 6 months and improved thereafter. However, from 1 year after transplantation onwards, the normal group demonstrated a significant increase in SMI compared with the low-tolerance group. Three years after transplantation, the median SMI in the normal group exceeded pretransplant levels and steadily increased, whereas in the low-tolerance group, there was little improvement and no return to baseline (P ≤ .05). Multivariable analysis identified low preoperative exercise tolerance as an independent predictor of reduced SMI recovery (P ≤ .05). Correlation analysis revealed that preoperative anaerobic threshold VO₂ and peak VO₂ were moderately and significantly associated with 3-year SMI improvement (r = 0.427 and r = 0.607, respectively).

Low exercise tolerance before kidney transplantation strongly predicts impaired long-term skeletal muscle recovery. Cardiopulmonary exercise testing-based risk assessment may help identify candidates who could benefit from tailored perioperative rehabilitation strategies to enhance functional outcomes.