Pre‐ and Post‐Kidney Transplant Abdominal Computed Tomography‐Based Muscle Measurements and Post‐KT Outcomes

Introduction Early post‐kidney transplant (KT) changes likely impact body composition, resulting in adverse post‐KT outcomes. We estimated post‐KT trajectories of computed tomography (CT)‐based muscle quantity/quality and tested whether they were associated with mortality and death‐censored graft loss (DCGL) among frail and nonfrail recipients. Methods We leveraged a cohort of 294 adult KT recipients (December 2008–February 2020) with CT measurements (muscle quantity: skeletal muscle index; muscle quality: skeletal muscle radiation attenuation). We used mixed linear regression models to estimate 3‐year post‐KT muscle quantity/quality trajectories. Cox proportional hazard models quantified the association between time‐varying pre‐/post‐KT muscle mass measurements and post‐KT mortality and DCGL. Results Muscle quantity (−2.4 cm 2 /m 2 /year) and quality (−1.3 HU/year) decreased during the first 2 years post‐KT and then remained constant in the third year post‐KT. Change in muscle quantity ( p interaction < 0.01) and quality ( p interaction = 0.01) differed by frailty in the first 2 years post‐KT; change in muscle quality ( p interaction < 0.01) differed by lower extremity impairment in the third year post‐KT. Among frail recipients, lower muscle quantity (per 10 cm 2 /m 2 ) was associated with elevated mortality risk (aHR: 2.00, 95% CI: 1.08–3.70), but not among nonfrail recipients. Among older (≥65 years) recipients, lower muscle quantity was associated with increased DCGL risk (aHR: 2.70, 95% CI: 1.04–7.04), but not among younger recipients. Lower muscle quality (per 10 HU) was associated with elevated mortality (aHR: 2.23, 95% CI: 1.61–3.08) and DCGL (aHR: 1.90, 95% CI: 1.16–3.12) risk. Conclusion Lower pre‐/post‐KT muscle quantity/quality were associated with higher risks of post‐KT adverse outcomes. Pre‐/post‐KT rehabilitation to improve muscle quantity/quality may be an effective clinical intervention to minimize risks of adverse post‐KT outcomes.