Evaluation of bone-mineral density by digital X-ray radiogrammetry (DXR) in pediatric renal transplant recipients

Background: Loss of bone mass and increased fracture risk are known complications after renal transplantation in adults. Risk factors include donor source, dialysis status prior to transplantation, aetiology of renal disease, transplant rejection and drug therapy, particularly steroids. Objective: In this preliminary study of quantification of bone loss in children after renal transplantion, we evaluated the applicability of digital X-ray radiogrammetry (DXR) of hand radiographs to estimate cortical bone mineral density (DXR-BMD). Materials and methods: A total of 23 renal transplant recipients (9 girls, 14 boys; age 6.5–20 years, median 16.3 years) underwent DXR measurements for calculation of DXR-BMD and metacarpal index (DXR-MCI) using radiographs of the non-dominant left hand. The duration between transplantation and the DXR evaluation, the duration of dialysis and medication were considered. The results were compared to a local age-matched and gender-matched reference data base. Results: Our study revealed a significant decrease in bone mineral density compared to an age-matched and sex-matched normal population (P<0.05). In three patients the DXR-BMD was reduced more than −2.5 SD. In 12 patients the DXR-BMD was between −1 and −2.5 SD, and in 7 patients the DXR-BMD was in the normal range. In one patient, evaluation was not possible. Fractures were documented in three patients following transplantation. Reduced DXR-BMD was not significantly associated with immunosuppressive therapy or the duration of dialysis, and there was no significant correlation between DXR-BMD and the time between transplantation and DXR evaluation. Conclusions: Paediatric renal transplant patients show reduced DXR-BMD. In this preliminary study we demonstrated that DXR-BMD seems to be a reliable technique for quantification of demineralisation following renal transplantation in children.