The impact of kidney transplantation on bone was poorly understood and fragmented. For a study, researchers sought to describe the progression of bone disease in the first year after transplantation. They conducted prospective, observational cohort research on patients who had been referred for kidney transplantation while on a steroid-free immunosuppressive treatment. Bone phenotyping was performed before or at the time of kidney transplantation, and it was repeated 12 months afterward. Bone histomorphometry, bone densitometry by dual-energy x-ray absorptiometry, and biochemical markers of bone and mineral metabolism were all used in the phenotyping.
For 97 cases, paired data were acquired (median age 55; 72% male; 21% of patients had diabetes). In the majority of patients, bone turnover remained normal or improved (65%). Bone histomorphometry demonstrated reductions in bone resorption (eroded perimeter, mean 4.6% pre- to 2.3% post-transplant; P<0.001) and disordered bone production (fibrosis, 27% pre- to 2% post-transplant; P<0.001). Whereas bone mineralization was normal in all but one patient before transplant, delayed mineralization was seen in 15% of patients one year later. Hypophosphatemia was linked to impairment in bone mineralization histomorphometric parameters. Bone mineral density changes were very varied, ranging from –18% to +17% each year. The cumulative steroid dosage was associated with bone loss at the hip, but hyperparathyroidism resolution was associated with a bone increase at both the spine and the hip.
Changes in bone turnover, mineralization, and volume following transplantation were linked to both steroid exposure and continuing mineral metabolism problems. Improved bone quality in kidney transplant patients might rely on optimal mineral metabolism management.