[(99m)Tc]-sestamibi parathyroid scintigraphy in chronic haemodialysis patients: static and dynamic explorations

The place of parathyroid gland imaging by [(99m)Tc](technetium)-sestamibi scintigraphy in uraemic patients with secondary hyperparathyroidism remains a matter of debate. The purpose of the present study was (i) to assess its value with respect to plasma intact parathyroid hormone (iPTH) levels and to surgical parathyroidectomy (PTx), and (ii) to explore the possibility of suppressing parathyroid [(99m)Tc]-sestamibi uptake by calcitriol.

In a first cross-sectional, static study 52 chronic haemodialysis (HD) patients with plasma iPTH levels between 14 and 2791 pg/ml (normal, 10-65 pg/ml) had a [(99m)Tc]-sestamibi scan, and 21 of them underwent surgical PTx. In a second longitudinal, dynamic study 14 chronic HD patients with advanced secondary hyperparathyroidism received short-term calcitriol treatment in an attempt to suppress [(99m)Tc]-sestamibi imaging of parathyroid glands. Calcitriol was given intravenously for 2 weeks, 2 microg after each haemodialysis session. Scintigraphy was carried out before and at the end of this inhibition test.

[(99m)Tc]-Sestamibi scan led to imaging of one or more (maximum three) parathyroid glands in most, but not all, HD patients with plasma iPTH values >600 pg/ml. Based on surgical findings, overall sensitivity of [(99m)Tc]-sestamibi scan in correctly locating parathyroid glands was only 50%, whereas specificity was 100%. In contrast, its sensitivity was 100% in locating single glands in the subgroup of five patients with recurrent hyperparathyroidism. The calcitriol inhibition test showed suppression of [(99m)Tc]-sestamibi uptake by at least one parathyroid gland in eight patients (57%), with complete suppression in five of them (36%). Basal plasma iPTH or decrease of plasma iPTH in response to calcitriol was not predictive of suppressible [(99m)Tc]-sestamibi uptake in the individual case, although mean iPTH was markedly higher in patients with non-suppressible parathyroid glands.

Because of its relatively low sensitivity the [(99m)Tc]-sestamibi scan is of limited help in the exploration of uraemic patients with severe secondary hyperparathyroidism before a first surgical PTx. However, it is very useful in locating the remaining parathyroid gland(s) in case of reoperation. The novel calcitriol inhibition test of [(99m)Tc]-sestamibi uptake could help to better distinguish parathyroid glands with non-suppressible, autonomous activity from glands whose activity might be amenable to long-term suppression.