[The role of scintigraphy with dual tracer and potassium perchlorate (99mTcO4 & KClO4/ MIBI) in primary hyperparathyroidism].

BACKGROUND: The diagnostic value of scintigraphy using a dual tracer and high-resolution neck ecotomography in the preoperative localisation of parathyroid enlargements was evaluated in a group of consecutive patients suffering from primary hyperparathyroidism (HPT) who were uniformly studied and subsequently operated by the same surgical team.

METHODS: Scintigraphic imaging and high-resolution neck ecotomography were carried out in a single session on 143 patients. Scintigraphic imaging was performed using a dual tracer, 99mTc-pertechnetate/99mTc-MIBI), modified by the addition of potassium perchlorate (KCL04) to achieve a rapid washout of 99mTc04 from the thyroid and, consequently, to achieve good quality and rapid MIBI images. In a limited number of patients (21 cases) SPECT was also performed. Limited surgery was planned in patients with evidence of single parathyroid lesions and with normal thyroid parameters, in the form of either unilateral or with mini-invasive surgery (91 cases). Patients with eco-scintigraphic evidence of multiglandular parathyroid pathology or the coexistence of a nodular thyroid goitre, or in patients suffering from MEN or familial HPT, or lastly those with negative eco-scintigraphic results under-went more extensive surgery with bilateral exploration of the neck (52 cases). A single parathyroid lesion was diagnosed during surgery in 90 out of 91 patients undergoing planned unilateral or mini-invasive exploration of the neck. Therefore, in our experience, the predictive value of preoperative imaging as a mean of identifying single parathyroid lesions was 98.9% with a clear impact on the choice of conservative surgery. After the removal of the parathyroid to which preoperative imaging referred, it was only necessary in one patient to extend surgical exploration to the other side of the neck to remove another enlarged parathyroid owing to persistent high PTH.

RESULTS: The sensitivity of scintigraphy and high-resolution neck ecotomography in pa-tients with a single adenoma was 94% and 83.7% respectively, whereas it was 76.9% and 64.5% respectively in the group of patients with multiglandular pathology. It is worth underlining that in all 31 patients with associated nodular thyroid pathology, the evaluation of thyroid scintigraphic imaging using 99mTc04 and high-resolution neck ecotomography enabled the preoperative diagnosis of thyroid pathology, therefore guiding the surgeon towards more extensive surgery. SPECT enabled the parathyroid adenoma to be correctly localised in a deep site in 5 patients, in the neck in 3 cases and at the mediastinum in 2 patients, providing additional data that helped the surgeon to plan surgery.

CONCLUSIONS: In conclusion, in our experience: a) an integrated diagnostic approach based on scintigraphy 99mTc04 & KCLO4/MIBI and high-resolution neck ecotomography was an extremely accurate mean of identifying patients with single parathyroid lesions before surgery, enabling them to undergo limited surgery, b) scintigraphy with a dual tracer might be the elective methods for studying patients with HPT because it allows the contemporary diagnosis of possible thyroid diseases. This aspect is extremely important in geographical areas with a high predominance of nodular thyroid pathology, c) SPECT scintigraphic analysis may be useful in some patients with suspected parathyroid adenoma localised in a deep seat, allowing a more precise identification of the latter and better surgical planning.