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. The authors analyzed the factors associated with persistent hypercalcemia after parathyroidectomy in kidney transplant patients and evaluated the appropriate extent of surgery.

Materials and methods: The authors 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. The authors 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 is greater than 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 (17.9 vs. 54.5%). 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 is less than 88% on postoperative day 1 (odds ratio 10.3, 95% CI: 2.7-39.1, P =0.001) and the removal of less than or equal to 2 parathyroid glands (odds ratio 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 is less than 88% on postoperative day 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.

Figure 1

Flow chart of study patients. KT, kidney transplantation; PTX, parathyroidectomy; THPT, tertiary hyperparathyroidism.

Figure 2

Biochemical characteristics and BMD of patients prior to parathyroidectomy. The numbers of patients with severe hypercalcemia and persistent hypercalcemia may overlap. BMD, bone mineral density; PTH, parathyroid hormone.

Figure 3

ROC curve of drop rate of parathyroid hormone on POD1 (AUC =0.836, P < 0.001, drop rate of PTH <88% → OR 13.1 [95% CI 3.90–43.20]). AUC, area under the ROC curve; OR, odds ratio; PTH, parathyroid hormone; POD, postoperative day; ROC, receiver operating characteristic.