The effect of hypercalcemia on allograft calcification after kidney transplantation.

PURPOSE: Persistent hypercalcemia after kidney transplantation (KTx) may cause nephrocalcinosis and graft dysfunction. The aim of this study was to evaluate patients with hypercalcemia and assess its effect on tubulointerstitial calcification.

METHODS: A total of 247 recipients were enrolled. Transient and persistent hypercalcemia was defined as hypercalcemia (corrected serum calcium >10.2 mg/dL) persisting for 6 and 12 months after KTx, respectively. The severity of calcification in the 0-h, 6- and 12-month protocol biopsies of patients with transient (n = 8) and persistent hypercalcemia (n = 20) was compared with a matched control group (n = 28).

RESULTS: Twenty-eight patients were hypercalcemic at 6 months posttransplantation. Serum calcium levels were normalized in eight of them at the end of the first year. Dialysis duration was a positive predictor of persistent hypercalcemia. Tubulointerstitial calcification was detected in 70.6 and 90 % of patients with persistent hypercalcemia at 6 and 12 months posttransplantation, respectively. In 20 % of patients with transient hypercalcemia, severity of calcification regressed at 12 months posttransplantation along with normalization of serum calcium levels. Graft functions and histopathological findings (ci, ct, ci + ct, cv, ah, percentage of sclerotic glomeruli) were not different at 6 and 12 months posttransplantation.

CONCLUSIONS: Hypercalcemia and persistent hyperparathyroidism are not rare after KTx. Tubulointerstitial calcification is more common and progressive among patients with persistent hypercalcemia. Normalization of calcium levels may contribute to regression of calcification in some patients.