Prevalence and predictors of early hypercalcemia after kidney transplantation: a nested case-control study within a cohort of 100 patients.

Background: Hypercalcemia (HC) after kidney transplantation (KTx) can deteriorate both graft and patient survival. However, HC as a clinical condition and its clinical significance after KTx remain unknown. We evaluated the prevalence and risk factors of early HC after KTx.
Methods: We performed a nested case-control study using a cohort of 100 KTx patients. KTx patients were divided into the HC and normocalcemia (NC) groups based on the baseline serum-corrected calcium (cCa) levels (≥ 10.5 and < 10.5 mg/dL) within 1 year after KTx.
Results: Overall, the median value of maximum serum cCa level within 1 year after KTx was 10.1 (9.1-13.8) mg/dL. Of the 100 KTx patients within the cohort, 31 patients (31.0%) were classified as the HC group. The maximum serum cCa level was reached significantly earlier in the HC group compared with the NC group (2 vs. 4 months, p = 0.024). In univariate analysis, the risk factors of early HC after KTx were dialysis duration ≥ 10 years, serum cCa level the day before KTx, and cinacalcet administration before KTx. Among these risk factors, serum cCa level the day before KTx and cinacalcet administration before KTx were identified as significant independent risk factors of early HC after KTx in multivariate analysis.
Conclusions: One-third of the KTx patients presented early HC within 1 year after KTx. Early HC after KTx resulted from persistent hyperparathyroidism. Therapeutic strategies to manage HC after KTx must be established.