Factors associated with statural growth in pediatric kidney transplant recipients with focus on metabolic acidosis

Background: We investigated factors associated with post-transplant growth in pediatric kidney transplant (KTx) recipients with a focus on plasma bicarbonate (HCO3⁻) and estimated the effect of alkali treatment on growth. Methods: In this study of the CERTAIN Registry, data were collected up to 5 years post-transplant. Generalized Additive Mixed Models were applied to assess the association between post-transplant growth and covariates. A trial-emulation analysis was performed to estimate the causal effect of alkali supplementation on growth. Results: We report on 2147 primary KTx recipients with a median age at KTx of 10.2 (IQR 5.1;14.3) years. No statistically significant association was found between growth and HCO3⁻ (p = 0.21), but the shape of the estimated conditional association showed a decreasing estimated growth with increasing HCO3⁻. Glucocorticoid treatment and allograft rejection showed an inverse association with growth. Living donor KTx, glomerulopathy, recombinant growth hormone use, low height z-score at KTx, younger age, and higher eGFR were positively associated with growth. The trial-emulation analysis included patients at 30 days and 3, 6, and 9 months post-transplant with HCO3⁻ < 22 mmol/L and no prior alkaline treatment. Alkaline treatment was initiated in 194, 93, 47, and 25 patients, respectively. After adjustment for confounders, there was no significant difference in growth at 1-year post-transplant in treated and untreated patients. Conclusions: We found no association between HCO3⁻ and growth nor evidence of improved growth after treatment of metabolic acidosis. Living donor KTx was positively associated with post-transplant growth, while there was an inverse association with allograft rejection.