Bone mineral disorders in pediatric and adolescent renal transplant recipients

Abstract

Incomplete resolution of abnormalities of mineral metabolism associated with CRF results in the relatively high prevalence of ROD in pediatric kidney recipients. This non-randomized, cross-sectional, and analytic-descriptive study on bone density, vitamin D, and mineral metabolism was performed in 57 children and adolescents who had received a total of 60 renal allografts in Shiraz, Iran. The height and weight of the patients were measured; their serum calcium (Ca), phosphorus (P), Alk-P, PTH, 25(OH)-vitamin D(3), BUN, creatinine, and electrolyte levels were analyzed, and a complete blood count was performed. In addition, standard radiologic bone assessments, which included conventional left hand-wrist radiography and bone mineral densitometry by the DXA technique, were carried out. Special pediatric software was used for age-related interpretation of the Z-scores of BMD. SPSS(®) software (version 15) was used for statistical analyses. We studied 57 patients (27 males [47.4%]) with a mean age of 18.7 ± 4.25 (9-27) yr and a mean age at transplantation of 13.1 ± 3.46 (4.5-20) yr. They had a post-transplantation follow-up of 67.1 ± 33.8 (6-132) months, and all had well-functioning allografts at enrollment. The mean height age of the patients was 11.9 ± 1.8 (6-15.5), and the mean bone age was 15.6 ± 3.3 (7-19) yr, which corresponded to mean height-age and bone-age retardations of 5.7 ± 2.3 (0.5-10.5) and 1.22 ± 1.47 (0-7) yr, respectively. Hyperphosphatemia and hypercalcemia were each found in nine patients (15.8%), hypophosphatemia in five (8.8%), and hypocalcemia in none of the patients. Seven out of 57 patients (12.3%) had a (Ca×P) product of more than 55 mg(2)/dL(2). Hyperparathyroidism was found in 27 (47.3%) and vitamin D(3) deficiency in four (7%) of the cases. The serum level of Alk-P was higher than the age-related normal range in 20 patients (35%). Left hand-wrist radiography showed no radiologic sign of ROD in any patient. The mean BMD Z-score was -1.77 ± 1.13 (-4.2-1.1) for the lumbar spine and -1.64 ± 0.89 (-3.9 to 1.9) for the femoral neck. "Stepwise backward regression" revealed a significant inverse correlation between the serum level of PTH and the GFR of the transplanted kidney; this correlation was independent from the influence of other variables such as Ca, P, and Alk-P (p = 0.011, β = -1.556). Bone age and height age both showed significant correlations with age at transplantation and serum levels of P (p < 0.001), but only bone age had a meaningful correlation with Alk-P (p = 0.036). The BMD Z-scores showed statistically meaningful correlations with the serum level of Alk-P, which were independent from the influence of other variables such as Ca, P, and PTH (p ≤ 0.002). Our study revealed a relatively high prevalence of bone mineral disorder in pediatric kidney recipients, which suggests the need for a routine program for periodic screening of these patients to facilitate early diagnosis of either persistent or evolving manifestations of disturbed mineral metabolism, especially ROD.

Mineral Metabolism in European Children Living with a Renal Transplant

“…Abnormalities in phosphorus levels were largely age dependent. Confirming previous reports (5,28,29), we observed that 25% of the patients had phosphorus levels outside target range. Hypophosphatemia was more prevalent than hyperphosphatemia, ranging from 67% in infants to 5% in adolescents.…”

Bone Density and Cortical Structure after Pediatric Renal Transplantation

“…[3][4][5][6][7][8][9][10][11] DXA is a projection technique that summarizes total bone mineral content within the projected bone area, resulting in two important limitations in childhood CKD. First, trabecular and cortical bone are superimposed, potentially concealing the opposing effects of elevated parathyroid hormone (PTH) levels to increase and decrease trabecular and cortical bone mineral content, respectively.…”

“…First, trabecular and cortical bone are superimposed, potentially concealing the opposing effects of elevated parathyroid hormone (PTH) levels to increase and decrease trabecular and cortical bone mineral content, respectively. 12 Second, DXA provides a two-dimensional measure of areal BMD (g/cm 2 ) that systematically underestimates volumetric BMD (g/cm 3 ) in children with poor growth. 13 This effect was illustrated in a study of pediatric renal transplant recipients: areal BMD Z-scores relative to chronological age were 1-2 SDs lower than areal BMD Z-scores relative to height age.…”

Mineral disorders in pediatric pre‐emptive kidney transplantation

“…Therefore, strict control of calcium and phosphorus is required to prevent the progression of chronic kidney disease mineral and bone disorder (CKD‐MBD) and CVD. A limited number of reports have examined the abnormalities in bone mineral metabolism in pediatric kidney transplant patients . Pre‐emptive kidney transplantation (PEKT) often provides good results .…”