Recent advances in parathyroid imaging

Parathyroid incidentaloma

Incidentalomas are lesions which are asymptomatic and detected incidently during imaging or surgery. Parathyroid incidentalomas are a rare entity. Enlargement of gland without hyperfunction may be an early stage of disease. Symptomatology is usually non-specific or related to renal and skeletal system. Total serum calcium estimation may be used as a screening modality. Sestamibi scan is a more accurate imaging technique than USG. FNAB - PTH measurement is the most reliable minimally invasive nonsurgical test for parathyroid tissue verification. Incidently discovered enlarged parathyroid gland may be removed to avoid a re-do surgery.

Parathyroid glands: combination of (99m)Tc MIBI scintigraphy and US for demonstration of parathyroid glands and nodules

PURPOSE

To determine the appropriate choice of imaging techniques for localization of nodular lesions of parathyroid glands.

MATERIALS AND METHODS

First, computed tomographic (CT), magnetic resonance (MR), ultrasonographic (US), and technetium 99m methoxyisobutyl-isonitrile (MIBI) scintigraphic images in 49 patients with primary hyperparathyroidism were retrospectively evaluated. A single-blind, prospective study that included 16 patients with primary hyperparathyroidism was then conducted. MR, US, scintigraphic, and color Doppler US images of the neck were obtained and analyzed.

RESULTS

In the retrospective study, CT, MR imaging, and US had low sensitivity (13%, 17%, and 27%, respectively) and specificity (39%, 65%, and 65%, respectively). Scintigraphy had 57% sensitivity and 85% specificity. In the prospective study, the use of latest-generation MR and US equipment and the participation of experienced operators led to improved sensitivity and specificity for these techniques. The combination of US and scintigraphy resulted in improved sensitivity (96%), specificity (83%), and positive and negative predictive values (88% and 94%, respectively), relative to the results obtained with either method alone. Doppler US was of little help in the setting of small glands.

CONCLUSIONS

The combination of (99m)Tc MIBI scintigraphy and US performed by well-trained operators with up-to-date instruments appeared to be the best diagnostic tool for the preoperative diagnosis of parathyroid disease.

Detection and diagnosis of parathyroid incidentalomas during thyroid sonography

PURPOSE

The aim of our study was to evaluate the incidence of incidentally found parathyroid adenomas (incidentalomas) in patients undergoing sonography of the neck for thyroid disease.

METHODS

A total of 1,686 patients (305 men and 1,381 women) underwent sonography of the neck; the mean age was 49.6 +/- 21.7 years. In 38 patients (2.3%; 7 men and 31 women) with a mean age of 48.7 +/- 14.7 years, hypoechoic, homogeneous, oval nodules (mean volume, 1.0 +/- 0. 9 cm(3)) adjacent to the thyroid parenchyma were observed. All these lesions, compatible with the shape of an enlarged parathyroid gland, underwent ultrasound-guided fine-needle aspiration biopsy (FNAB), with measurement of parathyroid hormone (PTH) and thyroglobulin (Tg) levels in the needle washings (FNAB-PTH and FNAB-Tg). Biochemical screening for hyperparathyroidism was also performed.

RESULTS

Cytologic examination plus FNAB-PTH/FNAB-Tg measurements revealed the presence of cellular material consistent with parathyroid tissue in 9 patients (24%), thyroid tissue in 22 patients (58%), and lymphoid tissue in 4 patients (11%). A tissue diagnosis was not established in 3 patients (8%). Five of 9 patients with parathyroid enlargement had high serum PTH and calcium levels.

CONCLUSIONS

Enlarged parathyroid glands may be incidentally discovered during sonography of the thyroid. In patients with thyroid disease, the positive-predictive value of sonography in the identification of parathyroid tissue was low. Ultrasound-guided FNAB-PTH determination should be carried out when parathyroid adenoma is suspected. The incidental finding of an enlarged parathyroid may or may not be associated with yet undiagnosed hyperparathyroidism.