*Purpose: Body composition has been found to be associated with the risks of post-kidney transplantation (KT) outcomes. However, it is unclear which pre-KT computed tomography (CT)-based measurements of body composition predict graft loss and mortality. Therefore, we estimated the association between pre-KT CT measurements of body composition and post-KT outcomes in FAIR cohort.

*Methods: We leveraged a perspective cohort of KT recipients (n=291) from 2008-2020 who underwent pre-KT abdominal CT scans in Johns Hopkins hospital within 1-year pre-KT that included the third lumbar vertebral level. Body composition measurements were obtained, including skeletal muscle index (SMI) and skeletal muscle radiation attenuation (SM-RA). Sarcopenia was defined as an SMI<50 cm²/m² for males and an SMI<39 cm²/m² for females. Myosteatosis was defined as an SM-RA<41 mean HU for recipient with a BMI<25 kg/m² and an SM-RA<33 mean HU for recipient with a BMI≥25 kg/m². Sarcopenic obesity was defined as a BMI≥30 kg/m² for sarcopenic recipients. Cox proportional hazard models were used to quantify associations of each measure with post-KT mortality and all-cause graft loss. P values <.05 were considered significant.

*Results: Among 291 recipients, 117 (40.2%) had sarcopenia, 202 (69.4%) had myosteatosis and 23 (7.9%) had sarcopenic obesity. Myosteatosis was associated with elevated hazard of both mortality (aHR: 2.16; 95% CI: 1.08, 4.32) and all-cause graft loss (aHR: 2.02; 95% CI: 1.11, 3.70) after adjusting for confounders. Neither sarcopenia nor sarcopenic obesity was associated with post-KT outcomes.

*Conclusions: Among the CT-based body composition measurements typically available pre-KT, myosteatosis was the only factor associated with post-KT outcomes, which could be a valuable tool for identifying recipients at elevated risk based on existing CT scans.

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