Combination of different imaging methods in the diagnosis of primary hyperparathyroidism: Is it really necessary?

The diagnosis of primary hyperparathyroidism (pHPT) is based in clinical and laboratory finding especially high blood calcium and increased parathormone levels. The combination of both is the most common presentation of the disease. Solitary parathyroid adenoma is the most frequent pathology found. Parathyroid hyperplasia or carcinomas are less frequent. The role of different diagnostic imaging procedures and their usefulness, alone or combined, before surgery, is still controversial. Aim: The aim of our study was to evaluate retrospectively the effectiveness and the usefulness of the combination of scintigraphy, ultrasound (US) and computed tomography (CT) in the diagnosis of pHPT. Materials and Methods: 55 charts of patients with clinical and laboratory diagnosis of pHPT were retrospectively evaluated. All selected patients underwent scintigraphy and US, 25 of them also had a CT study. Diagnosis was confirmed in all the cases by surgery. Results: A total of 71 lesions were removed at surgery: 55 of them corresponded to enlarged parathyroid glands (50 adenomas, 4 carcinoma and 1 lipo adenoma), and 16 to thyroid abnormalities (7 multi nodular goiter, 6 papillary carcinoma, 2 follicular carcinoma and 1 Hashimoto's thyroiditis). Thyroid nodular disease was present in 15 (27%) patients with pHPT and was associated with parathyroid adenoma in 13 (87%) of these patients. The minimal weight of parathyroid gland for successful imaging by scintigraphy, US and CT was 136 mg, 291 mg and 300 mg respectively. The smaller parathyroid gland found at surgery weighed 106 mg and all the preoperative imaging techniques failed to detect it. Scintigraphy had 89% sensitivity, 100% specificity, 100% PPV and 73% NPV. US had 85%, 94%, 98% and 73% respectively. CT had 71%, 87%, 94% and 50% respectively. The combination of scintigraphy and US resulted in improved sensitivity (93%), specificity (100%), PPV (100%) and NPV (75%). The combination of all the three methods did not improve effectively the results (94%, 100%, 100% and 66% respectively). Conclusion: The combination of scintigraphy and US appeared to be the best imaging approach for the preoperative diagnosis of pHPT. There is no need for CT when both scintigraphy and US clearly demonstrate parathyroid pathology. Scintigraphy seems to be the best imaging method to evaluate patients suffering from both pHTP and thyroid nodular diseases