Accuracy of Sestamibi Scans to Determine Parathyroid Pathology Examined

Patients who undergo kidney transplantation may develop tertiary hyperparathyroidism (ThPT) after successful renal transplantation. The incidence of ThPT, typically described as persistent hyperparathyroidism, may be as high as 50% in renal transplantation patients.

The hyperparathyroidism often resolves in a few months following transplant, with or without medical treatment. The occurrence of ThPT increases with the duration of dialysis before transplantation and with the severity of pretransplant hyperparathyroidism.

Among transplant patients, the incidence of parathyroidectomy (PTx) is reported to be between 1.3% and 20%. However, there are no guidelines for when to refer patients for parathyroidectomy. Previous studies have resulted in mixed results.

Zahra Deen, MD, and colleagues recently conducted a single-center, retrospective study designed to assess the accuracy of sestamibi scans to determine parathyroid pathology in patients undergoing kidney transplantation. The researchers reported results during a poster session at the National Kidney Foundation 2015 Spring Clinical Meetings in a poster titled Kidney Transplant Recipients Who Underwent Parathyroidectomy for Tertiary Hyperparathyroidism.

The researchers identified transplant recipients who underwent kidney transplantation between 2008 and 2013 and who underwent PTx for ThPT at Houston Methodist Hospital, Texas. Collected data included demographic and clinical information, as well as serum calcium, phosphorus, vitamin D, and intact PTH (iPTH) levels both pre-transplant and at 1, 3, 6, and 12 months following transplantation. Other clinical data of interest were measurements of bone density and parathyroid scans.

Among the 1001 patients who underwent kidney transplantation at Houston Methodist Hospital during the 5-year study period, the researchers identified 26 (2.5%) who underwent PTx. Mean age was 52 years and 58% (n=15) were women. Most (88%) underwent deceased donor transplantation and all were on tacrolimus, mycophenolate, and prednisone.

Mean calcium and iPTH levels pre-transplant were 10.4 mg/dL and 508 pg/mL, respectively. Median time duration between transplantation and PTx was 482 days.

Persistent hypercalcemia and significant osteoporosis or worsening osteopenia (or both) were indications for PTx (42%, 35%, and 15%, respectively). Eight percent of patients underwent surgery after failing medical therapy, including calcimimetics.

Glandular hyperplasia was seen in 50% of patients by sestamibi scan, as was adenoma in 34% of patients. However, surgical pathology showed hypercellular parathyroid tissue in 25 specimens (96%). Only one biopsy showed parathyroid adenoma with thick, fibrous trabecular and calcifications.

In their conclusions, the researchers said, “In our single-center retrospective study we found 26 patients who underwent parathyroidectomy with the most common indications being persistent hypercalcemia and osteoporosis or worsening osteopenia. These indications were similar to those found in other single-center studies.

“Additionally, parathyroid hyperplasia was the most common surgical pathology in these patients. Sestamibi scan was inaccurate in distinguishing between hyperplasia and adenomas in this patient population. To the best of our knowledge, this is the first study looking at the accuracy of sestamibi scans to determine parathyroid pathology in transplant patients.”

Source: Deen Z, Zwecker B, Asham EH, Gaber AO, Hong DM, Troung L, Mandayam S, Ramanathan V. Kidney transplant recipients who underwent parathyroidectomy for tertiary hyperthyroidism. Poster presented at the National Kidney Foundation Spring Clinical Meetings, March 2015, Dallas, Texas.