Background: Minimally invasive parathyroidectomy relies on accurate localisation of the culprit gland. Combination of US plus Technetium 99m-sestamibi is considered the gold standard. CT parathyroid is thought to be a valuable tool in the pre-operative localisation.
Aim: To evaluate the diagnostic performance of 2D CT parathyroid in patients with primary hyperparathyroidism (PHP).
Methods: This was a single-institution prospective study of patients with PHP who underwent a combined imaging protocol of US and CT (US+CT) parathyroid from January 2017 to January 2019, with subsequent parathyroidectomy. Sestamibi was reserved for patients with diagnostic uncertainty. The reference standard for correct localisation was basis on intraoperative PTH, histology and biochemical confirmation on follow up (at least 6 months).
Results: Seventy-five patients were evaluated with combined US+CT. Total 54 (72.0%) had sestamibi of which 47 patients were referred with scan performed elsewhere. CT correctly identified a target in 63 (84%). In 17 patients CT was the only modality correctly localised parathyroid adenoma. The diagnostic accuracy of US+CT was superior to US and sestamibi (88% and 65% respectively; P<0.001). 21 patients (28%) had an ectopic adenoma, 9 (22%) had multi-glandular disease and 36 (48.0%) with parathyroid weighted <1.0 g. Within these subgroups, CT alone was superior to US+sestamibi for ectopic adenoma (82% and 57% respectively; P=0.07). The combination of US+CT increased accuracy to 86% P=0.016 for ectopic adenoma. CT showed higher sensitivity than US and sestamibi for smaller adenomas <1.0g (81% and 62% respectively, P=0.04). The correct pre-operative diagnosis of multi-glandular disease is most difficult, with similar accuracy for US+sestamibi and US+CT (40% and 50%, respectively, P>0.99).
Conclusion: The combination of US+CT provided a superior pre-operative localisation in 88% of patients, with relatively better diagnostic accuracy for smaller or ectopic adenomas and should be considered as a first-line imaging modality.