Predictive factors for persistent hypercalcemia following parathyroidectomy in patients with persistent hyperparathyroidism after kidney transplantation: A retrospective cohort study

Abstract

Background: Surgery for irreversible hyperparathyroidism is the preferred management for kidney transplant patients. We analyzed the factors associated with persistent hypercalcemia after parathyroidectomy in kidney transplant patients and evaluated the appropriate extent of surgery. Materials and Methods: We retrospectively analyzed 100 patients who underwent parathyroidectomy because of persistent hyperparathyroidism after kidney transplantation at a tertiary medical center between June 2011 and February 2022. Patients were divided into two groups: 22 with persistent hypercalcemia after parathyroidectomy and 78 who achieved normocalcemia after parathyroidectomy. Persistent hypercalcemia was defined as having sustained hypercalcemia (≥10.3 mg/dL) 6 months after kidney transplantation. We compared the biochemical and clinicopathological features between the two groups. Multivariate logistic regression analysis was used to identify potential risk factors associated with persistent hypercalcemia following parathyroidectomy. Results: The proportion of patients with serum intact parathyroid hormone (PTH) level >65 pg/mL was significantly high in the hypercalcemia group (40.9% vs. 7.7%). The proportion of patients who underwent less than subtotal parathyroidectomy was significantly high in the persistent hypercalcemia group (19.2% vs. 50%). Patients with a large remaining size of the preserved parathyroid gland (≥0.8 cm) had a high incidence of persistent hypercalcemia (29.7% vs. 52.6%). In the multivariate logistic regression analysis, the drop rate of intact PTH <88% on postoperative day (POD) 1 (odds ratio [OR] 10.3, 95% confidence interval [CI]: 2.7–39.1, P=0.001) and the removal of≤2 parathyroid glands (OR 6.8, 95% CI: 1.8–26.7, P=0.001) were identified as risk factors for persistent hypercalcemia. Conclusion: The drop rate of intact PTH <88% on POD 1 and appropriate extent of surgery for controlling the autonomic function were independently associated with persistent hypercalcemia. Confirmation of parathyroid lesions through frozen section biopsy or intraoperative PTH monitoring can be helpful in preventing the inadvertent removal of a parathyroid gland and achieving normocalcemia after parathyroidectomy.