Bone disease in patients with long-term renal transplantation and normal renal function

Abstract

Renal osteodystrophy may persist during the early years after renal transplantation. However, information on bone status after a successful long-term renal transplantation is limited. We examined biochemical parameters, bone mineral density (BMD), and bone histomorphometry in 25 asymptomatic men with normal renal function after 7.5 +/- 5.7 years of a renal transplantation. Serum calcium, phosphorus, alkaline phosphatase, and 1,25(OH)(2)D(3) levels and urinary calcium level and cyclic andenosine monophosphate excretion were within normal range in all patients. Serum intact parathyroid hormone (PTH) level was elevated in 11 subjects (133.6 +/- 78 pg/mL) and normal in the other 14 subjects (47.9 +/- 13.6 pg/mL). Mean BMD at the lumbar spine and femoral neck was low in the entire group. However, it progressively increased as time after transplantation increased, approaching normal values after 10 years. Bone histomorphometric analysis showed bone resorption, osteoid volume, and osteoid surface greater than normal range in the majority of patients. Bone formation rate and mineralization surface were low, and mineralization time was delayed in most patients. These lesions were more severe in patients after 3 to 4 years of transplantation but improved with time and approached normal values after a period of 10 years. PTH values did not correlate with bone histological characteristics or BMD. These results show that the bone alterations observed after long-term renal transplantation consist of a mixed bone disease in which features of high bone turnover coexist with altered bone formation and delayed mineralization. These findings may result from the combined effect of preexisting bone disease and immunosuppressive therapy.