Bone mineral density in pediatric patients after renal transplantation

To evaluate the natural history of bone mineral density after successful renal transplantation (TPL) modulated by therapeutic strategies in pediatric patients we have studied peripheral and partially proximal quantitative computed radius tomography (XCT) differentiating between trabecular (TBD), cortical (CBD) and total bone density (BD) cross-sectionally in a group of 24 subjects (mean age 17.1 +/- 7.0 y, mean Scr 1.66 +/- 0.89), 66.1 months (5-260) post transplant and compared the results with 12 controls. After TPL median TBD was elevated (182.5 vs. 155.5 mg/cm3) whereas the opposite was true for CBD (361.8 vs. 437.8 mg/cm3). The physiologic age dependency of BD had got lost after TPL but could be reassumed by the measurement of proximal CBD. TBD correlated with the cumulative calcitriol dosage (r = 0.60, p < 0.05), bone alkaline phosphatase (r = 0.55, p < 0.01), the Ca x P product (r = 0.43, p < 0.05) and inversely with the time after TPL (r = -0.45, p < 0.05), but no significant correlation could be detected with the cumulative steroid dose. It was found to be higher in calcitriol treated than in vitamin D3 treated patients. Proximal CBD was inversely correlated with bone alkaline phosphatase (r = -0.71, p < 0.01) and intact PTH (r = -0.59, p < 0.05). In conclusion CBD in kidney grafted pediatric patients seems to be more or less reduced by secondary hyperparathyroidism whereas the increase of TBD appears to be induced by anticipated calcitriol treatment under dialysis regimen and gradually normalizes after TPL.