Patrick Perkins, MD
Wayne Leonhardt, BA, RT, RDMS, RVT
Summit Sutter Medical Center Diagnostic Imaging
Oakland, CA

This patient is a 36 year old African-American female with a two year history of hypercalcemia. Several evaluations had been performed to monitor this condition. Recent tests revealed a calcium run of 12.8 to 13 and a phosphorus that was 1.7 to 1.8. Her intact PTH level was done a few months previously and was 238 with a normal range of 10-65 mg/dl. Patient complained of having been dehydrated recently and felt the need to drink large amounts of water. She has a history of fatigue and nonspecific aches and pains. Patient's medical history included asthma, sickle cell trait, and migraines. There is no history of hypertension, diabetes or heart disease. Upon physical examination, the patient was found to be a well-developed, well-nourished African-American female in no acute distress.

Clinical Diagnosis
Enlarged parathyroid gland and hypercalcemia. The ultrasound examination showed a 3.0 x 1.1 x 1.7 cm mass in the upper pole of the left lobe of the thyroid which shows marked hypervascularity. The left lobe of the thyroid is otherwise unremarkable. The right lobe is unremarkable except for a tiny cyst of 5mm dimension in its mid pole. The hypervascular heterogeneous mass at the upper pole of the left lobe of the thyroid, which in the clinical setting off hyperthyroidism is suspect for a parathyroid adenoma. The patient underwent surgery for a parathyroidectomy. The findings at surgery were: The left upper parathyroid was indeed enlarged consistent with an adenoma. The inferior gland on the left side was also inspected and was small. A cursory examination of the right neck failed to reveal any enlarged masses. Pathology report: Cellular parathyroid tissue, 2.4 grams. Consistent with parathyroid adenoma.

The following overview includes excerpts of an article written by Wayne Leonhardt, BA, RT, RDMS, RVT

Parathyroid Sonography
High-resolution sonography (7.5-15MHz) is the imaging modality recommended for the initial evaluation of patients with primary hyperparathyroidism. The overall accuracy of sonography in detecting parathyroid adenomas is approximately 75 to 80%. Color and power Doppler have an overall accuracy of 94% in locating abnormal parathyroid adenomas. The presence of an extrathyroidal artery leading to an adenoma aids in the detection of an otherwise inconspicuous parathyroid gland. When sonography fails to identify abnormal parathyroid glands preoperatively or postoperatively, scintigraphy, computed tomography, or magnetic resonance may be required to evaluate the mediastinum and retrotracheal areas that are not well seen with ultrasound. The overall accuracy of each imaging modality in localizing parathyroid adenomas is approximately 75%.
When a combination of these imaging modalities are used, the sensitivity of detection increases up to 90%. Fine needle aspiration with ultrasound guidance is helpful in postoperative localization of parathyroid adenomas with a reported sensitivity approaching 100%.

Parathyroid Sonographic Anatomy and Pathology
The most common clinical situation for parathyroid imaging is hypercalcemia (serum calcium levels greater than 10.5 mg/dl). Both primary and secondary hyperparathyroidism result in hypercalcemia. Primary hyperparathyroidism is caused by a solitary parathyroid adenoma in 80-90% of cases, by multiple glands in 10-20%, and by parathyroid cancer in less than1%. Secondary Hyperparathyroidism develops not because of any intrinsic abnormality of the parathyroid glands, but as a result of chronic renal failure or malabsorption. In secondary hyperparathyroidism all four glands are usually abnormal. The typical sonographic appearance of a parathyroid adenoma is seen as an oval, homogeneous hypoechoic, low echogenicity mass without through transmission that measures slightly greater than 1 cm in length. With enlargement, increased lobulation, inhomogeneity, cystic change, and occasional calcifications can be seen. Parathyroid adenomas range from small (5 x 3 x 1 mm) to giant, greater than 30 mm in one dimension. Giant adenomas have been described as large as 5 cm. Most parathyroid adenomas are 0.8-1.5 cm in length and weigh 500-1,000 mg. Thyroid nodules can be detected in approximately 25-46% of patients with hyperparathyroidism. Color flow imaging of enlarged parathyroid adenomas demonstrates a hypervascular pattern in 90% of cases. In 10% of cases, parathyroid glands are avascular. This occurs when the parathyroid glands are small (less than 1 cm), located deep in the neck, and when there are tumors with large areas of necrotic degeneration. Parathyroid cysts usually develop within the inferior glands close to the lower pole of the thyroid. They have the same appearance of thyroid colloid changes. Most patients with parathyroid cysts are normocalcemic, but the fluid within the cyst has a high PTH level. Parathyroid cancer is rare and accounts for only .5-1% of cases of primary hyperparathyroidism. Carcinomas are large measuring approximately 3.5 cm in diameter, in contrast to adenomas measuring about 1 cm.. Patients present with a palpable neck mass and profound hypercalcemia greater than 14.0 mg/dl. Carcinomas frequently have a lobulated contour and heterogeneous internal structure with cystic components. They often adhere to contiguous anatomic structures .

Pitfalls in Diagnosis of Parathyroid Adenomas
The minor neurovascular bundle, longus colli muscle, adjacent veins, collapsed esophagus, and lymph nodes, can simulate parathyroid adenomas. The minor neurovascular bundle has a maximum diameter of 5 mm and can be confused with a normal parathyroid gland. Asymmetry of the longus colli muscle may mimic a parathyroid adenoma on a transverse image. A collapsed esophagus may be mistaken for an adenoma. Lymph nodes may mimic ectopic parathyroid tissue, especially in postoperative thyroid patients.

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