Bone mineral density in pediatric and adolescent renal transplant patients: how to evaluate.

Reduced bone mass is a common complication of renal transplantation in adults but only few data are present for pediatric transplant patients. Bone mineral status of pediatric renal transplant patients ages ranging from 7.5 to 17.6 years (mean age 14.9 +/- 2.3) who were at least 6 months postrenal transplantation was examined. Bone mineral density (BMD) of lumbar vertebrea and femoral neck was determined by dual energy X-ray absorptiometry (DEXA) and z-scores according to age, puberty, height and bone age were compared to sex and ethnic specific reference data. z-scores were calculated for both areal and volumetric bone density. BMD L1-4 z-scores were more than 2 SD below the mean according to chronological age in 12 patients (63%), pubertal status in six patients (31.5%), bone age in five patients (26.3%) and height in five patients (26.3%). The BMD femoral neck z-scores were more than 2 SD below the mean according to age in 10 patients (55.5%), puberty in five patients (27.7%), bone age in three (16.6%) patients and height in five (26.3%) patients. Correction of the vertebrae and femoral neck for bone size yielded osteoporotic values for seven patients (36.8%) for lumbar BMD and for four patients (22%) for femoral neck BMD. The use of aBMD in growth-retarded children has some restrictions in determining z-scores. Deficits in spinal bone density still persisted after correcting for height, puberty, bone age and volume. In renal transplant patients who have short stature it is reasonable to give values corrected for height, puberty, bone age and bone size and interpret each of these values for each patient.