[value of bone densitometry in pediatric renal transplantation]

Renal transplantation improves many bone abnormalities inherent to chronic renal insufficiency, but also introduces new deleterious factors, especially those related to immunosuppressive drugs. We have studied the bone mineral content of 40 pediatric renal transplant recipients; moreover, we have analyzed its possible relationships with phosphorous-calcium metabolism, graft function and duration, steroid treatment and growth.

Bone mineral content was measured by dual energy X-ray absorptiometry (DEXA). The results were expressed as a z score in relation to age and sex. Immunosuppression was achieved by using triple therapy: azathioprine, cyclosporine A and prednisolone. At the time of the DEXA, 59% of the patients were on daily steroid treatment and 41% on alternate-day treatment.

All patients presented bone mass losses with a maximal decrease between 5 and 21 months post-transplantation and a posterior tendency to recovery. Fifty percent of the children had severe osteopenia (bone mineral density < -1 SD). There was no statistically significant association between the severity of bone loss and values of ionized calcium, phosphorus, intact PTH, or calcitriol received. However, a linear correlation was found between cumulative steroid dose and osteopenia (r = -0.35, p < 0.05). Height and growth velocity were more affected in the severe osteopenia group. In this group, the proportion of children on daily steroid treatment was statistically higher (72% vs 45%, p < 0.05).

Bone densitometry is an accurate, rapid and noninvasive method to measure renal transplant impact on the growing skeleton and it must be done in a periodic and standardized way.