Weight-/height-related bone mineral density is not reduced after renal transplantation

Abstract

Growth retardation is a frequent finding in patients after renal transplantation (Tx). Areal bone mineral density (BMD) in these patients has usually been reported to be low for age. We investigated the possible influence of height and weight retardation on the measurement of BMD in lumbar spine (BMD(L2-4)) and total body (BMDbody) using dual-energy X-ray absorptiometry in 44 (13 female) pediatric Tx patients with a median age of 13.1 (range 3.3-23.1) years. Patients were studied at 2.9 (range 1-10) years after Tx. Median body height in female and male patients was -2.10 (-3.6 to -0.3) and -2.35 (-5.3 to +1.0) standard deviation score (SDS), respectively. BMD expressed as grams per square centimeter bone area according to age was below the 5th percentile in 10 of 44 patients, but only 1 patient had low values for BMD(L2-4), and none for BMDbody, when the data were corrected for height or weight. BMDbody was closely correlated with height, weight, and body surface area (r=0.88), whereas the correlation for BMD(L2-4) was less (r=0.76). In 6 patients who achieved final height, height SDS was -2.27 (-4.3-0.4). Z-scores for BMDbody related to age, height, and weight were -1.0 (-2.6 to -2.3), 1.25 (0.1-3.4), and 0.81 (0.0-2.4), respectively. There was no age-dependent change when areal BMD values (g/cm2) were corrected for vertebral size to obtain bone volumetric density (BMDvol, g/cm3). Independent of height, cumulative methylprednisolone dose correlated negatively with BMD(L2-4) only in patients who had received a total dose of more than 6 g/m2 of the drug (r = -0.54, P= 0.045). In conclusion, BMD in pediatric patients after Tx is no longer diminished when the data are corrected for height or weight rather than age, or when the data are expressed as bone volumetric density.