Imaging description

Classically, the parathyroid glands are situated posterior to the thyroid gland at the mid-superior and inferior pole bilaterally, and they are not easily detectable on cross-sectional imaging when they are normal. Up to 35% of lower parathyroid glands are ectopic, however, and may be present anywhere from the angle of the mandible to the lower anterior mediastinum.

A parathyroid adenoma is a benign neoplasm that secretes excessive parathyroid hormone (PTH), resulting in hypercalcemia. Due to its unpredictable location and hypermetabolic activity, Tc-99m sestamibi scintigraphy is considered to be the most specific technique to detect a parathyroid adenoma, although its sensitivity may be limited in small adenomas [1]. Ultrasound, CT, or MRI are used for anatomic correlation [2]. Recently, multiphasic contrast-enhanced CT, which can demonstrate contrast wash-in and wash-out characteristics of adenomas, has gained popularity, as it appears to have greater sensitivity and specificity compared to other techniques. Selective venous sampling of PTH for localization of parathyroid adenoma is reserved for complex postoperative cases where cross-sectional imaging and nuclear scintigraphy are inconclusive.