CHANGES IN BONE MASS EARLY AFTER KIDNEY-TRANSPLANTATION

Renal transplant patients exhibit increased rates of trabecular bone f ractures, probably due to glucocorticold-induced osteopenia, which is known to occur within 6 months after kidney grafting. This mineral los s at a mostly trabecular site (lumbar spine) contrasts with a gain at the radius, which consists mainly of cortical bone. However, the early effects of kidney transplantation on the other parts of the human ske leton and the time course of these changes during the first 5 months a fter transplantation remain unknown. Therefore, 34 kidney transplant r ecipients were prospectively followed immediately after kidney graftin g (12 +/- 1 days, mean +/- SEM, and then on a monthly basis up to 152 +/- 3 days) and compared with 34 normal healthy volunteers matched for age, sex, and body mass index. Bone mineral measurements of whole bod y (n = 34), lumbar spine(n = 32), and upper femur(n = 23) were perform ed using dual-energy x-ray absorptiometry (Hologic QDR 1000(W)). At ti me of transplantation, lumbar bone mineral density (BMD) and BMD of th e upper femur were tower (p < 0.01) in female but not male patients co mpared with controls. Lumbar BMD decreased by 1.6 +/- 0.2% per month i n both sexes (p < 0.01), whereas BMD of upper femur further decreased in males (p < 0.01) but only tended to decrease in females. At time of transplantation, whole-body bone area (BA), bone mineral content (BMC ), and BMD were decreased by about 8, 15, and 9%, respectively, in pat ients compared with controls (p < 0.01). Compartmental analysis reveal ed similar reductions in BMD and BMC at trunk, head, and limbs, wherea s BA was reduced only at limbs Cp < 0.01). During the 152 +/- 3 days o f observation, BMC and BMD of limbs remained essentially unchanged, wh ereas BA of limbs increased (p < 0.01) and BA, BMC, and BMD of trunk a nd head decreased (p < 0.01). In conclusion, within 5 months after suc cessful kidney transplantation resulting in good renal function, about 41g bone mineral is lost, mostly due to losses in the trabecular bone compartment (i.e., about 10%). Longitudinal trials to prevent trabecu lar bone loss during the phase of terminal renal failure and during th e first half-year following transplantation are urgently needed to dev elop rational and effective therapeutic strategies in patients on dial ysis and kidney transplant patients.