Clinical manifestations of hypercalcemia and hypophosphatemia after kidney transplantation

Introduction: Abnormalities of calcium and phosphorus metabolism in end-stage renal disease patients can persist after transplantation. We investigated their natural courses after transplantation, their risk factors for posttransplantation hypercalcemia and hypophosphatemia, and their impacts on allograft outcomes. Methods: We retrospectively analyzed a total of 490 adult patients who underwent kidney transplantations between 2000 and 2009. Results: The serum calcium continued to increase, and reaching a plateau at around 3 months after transplantation. Thereafter it decreased, reaching a stable level by 2 years. Forty-four patients (9.0%) displayed hypercalcemia within 1 year; it persisted longer than that in 23 subjects (4.7%). Both longer dialysis duration (odds ratio [OR] 1.423; 95% confidence interval [CI], 1.192-1.699) and high intact serum parathyroid hormone (iPTH) level before transplantation (OR 1.002; 95% CI, 1.000-1.003) increased the risk for posttransplantation hypercalcemia. After a significant decrease during the first week, the serum phosphorus level increased, becoming stable between 1 and 6 months after transplantation. Hypophsphatemia occurred in 379 patients (77.3%) with 336 patients displaying hypophosphatemia without hypercalcemia. However, neither hypercalcemia nor hypophosphatemia influenced graft outcomes. Eight patients underwent pretransplantation parathyroidectomy, whereas 4 patients underwent posttransplantation parathyroidectomy. Neither group of patients experienced posttransplantation hypercalcemia. Conclusions: Both hypercalcemia and hypophosphatemia are common after renal transplantation, especially among patients with a long history of dialysis before transplantation. Strict control of hyperparathyroidism including parathyroidectomy before transplantation may be the appropriate approach to these abnormalities.