*Purpose: Children with end stage renal disease on dialysis are known to be at high risk for protein energy wasting and low muscle mass, however less is known about muscle strength and physical functioning of children after kidney transplant. In adult transplant recipients, low muscle strength has been associated with decreased physical quality of life (QOL), mortality and hospitalization. We hypothesized that low muscle strength and physical functioning may be prevalent in pediatric kidney transplant recipients and we aimed to investigate factors associated with hand grip strength (HGS) in this population.

*Methods: This was a cross-sectional retrospective analysis of a cohort of 64 pediatric kidney transplant recipients (>6 months post-transplant) who had HGS measured as part of a nutritional assessment between 2017-2019. A subset of 29 participants also had Physical Functioning assessed by a psychologist using parent and/or child versions of the PedsQL Core Module, a measure of health-related pediatric QOL (scored 0-100, 100 being highest QOL). HGS was measured in the dominant hand and converted to age and sex-specific z-scores based on published normal pediatric data. Multivariable linear regression was used to identify associations of demographic and clinical characteristics with HGS.

*Results: Demographics and clinical characteristics of the study population are summarized in Table 1. Overall mean Physical Functioning score and 95%CI by PedsQL were 80.17 (70.6 to 89.7) by parent report and 82.84 (74.8 to 90.8) by child report. Lowest item scores were reported for child’s ability to “lift something heavy” (59.4, 43.7 to 75.2) and “do sports activity or exercise” (72.7, 57.5 to 87.9) by child and parent report, respectively. HGS of pediatric kidney transplant recipients was lower compared to normal pediatric reference values, evidenced by mean HGS z-score of -1.17. Multivariable analysis showed lower HGS z-score was independently associated with CAKUT diagnosis (-1.4 + 0.37, -2.2 to -0.67, p=0.0001). Increased HGS was associated with higher height z-score (0.41 + 0.13, 0.15 to 0.67, p=0.003) and higher hemoglobin (0.25 + 0.11, 0.03 to 0.49, p=0.03).

*Conclusions: Pediatric kidney transplant recipients exhibit deficits in muscle strength and physical functioning, evidenced by lower HGS compared to healthy peers and PedsQL report. Children with CAKUT diagnosis may have lower muscle strength due to effects of longstanding disease on bone health and muscle development. Anemia and impaired growth also negatively impact HGS after transplant. Strategies to promote muscle strengthening after kidney transplant should be emphasized.

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