Bone mineral density and bone histomorphometry in children on long-term dialysis

Bone mineral density (BMD) at the lumbar vertebrae (L-1-L-4) was assessed by dual-energy X-ray absorptiometry (DXA) in 20 children with chronic kidney disease (CKD) on dialysis, and its results were compared with bone biopsy and biochemical parameters. Biopsy specimens provided evidence of hyperparathyroid bone disease in eight cases (40%), and low bone turnover in 12 (60%). For BMD, expressed as Z-scores relative to normal, median Z-scores were -1.05 (range -2.36 to 1.06) for hyperparathyroid patients and -1.05 (range -4.40 to -0.03) for low bone turnover patients, with no statistical differences between groups (P=0.512). In relation to BMD, of the whole sample, five (25%) had a Z-score under -2.0. When it was corrected for height, BMD was in the normal range. Additionally, there were no significant differences in single samples of serum calcium, alkaline phosphatase, phosphorus and intact parathyroid hormone (PTH) between groups with high or low bone turnover. Assessment of nutritional status, through height/age, showed that ten patients had Z-scores below -2.0 (median -2.12, range -7.13 to 0.73). In conclusion, renal osteodystrophy (ROD) seems to have a high prevalence among CKD pediatric patients, although only approximately a quarter of them developed changes in BMD. In children with CKD, measurements of bone mineral density may not be used for classification of various forms of ROD.