A parathyroid adenoma is a non-cancerous tumor on one of the four parathyroid glands in the neck, which regulate the body’s calcium. An adenoma can cause the gland to produce excessive parathyroid hormone (PTH), leading to primary hyperparathyroidism. This condition elevates blood calcium levels, affecting various bodily systems over time. To investigate the source, physicians use imaging tests, with ultrasound being a common tool for examining the neck.
The Purpose of Parathyroid Ultrasound
The primary role of a parathyroid ultrasound is not to diagnose hyperparathyroidism, but to locate the problematic gland before surgery. The diagnosis is established through blood tests that show high levels of calcium and parathyroid hormone. Since the treatment for a parathyroid adenoma is surgical removal, knowing the tumor’s precise location allows for a more focused, minimally invasive procedure. This targeted approach leads to smaller incisions and a shorter recovery time.
Ultrasound is often the first imaging modality used because it is non-invasive, does not use ionizing radiation, is widely available, and is less expensive than other techniques. An experienced operator can use ultrasound to scan the neck, differentiating the parathyroid glands from adjacent tissues to pinpoint the adenoma.
The effectiveness of the ultrasound depends on the operator’s skill. Surgeons specializing in parathyroid procedures often perform their own ultrasounds. Their direct experience in the operating room provides an advantage in interpreting the images, allowing them to correlate sonographic findings with the anatomy they will encounter during surgery. This integration of imaging and surgical expertise increases the precision of the localization.
Sonographic Features of a Parathyroid Adenoma
During a parathyroid ultrasound, the operator looks for specific visual markers of an adenoma. It appears as a distinct, solid, oval-shaped mass that is “hypoechoic,” meaning it looks darker on the screen than the surrounding thyroid tissue. This contrast helps distinguish the abnormal gland from the normal tissue around it.
The location of the mass is another indicator. Most parathyroid adenomas are found on the posterior side of the thyroid gland. An enlarged parathyroid gland is often delineated by a thin, bright line of connective tissue separating it from the thyroid. However, adenomas can sometimes develop in atypical (ectopic) locations within the neck or chest, making them harder to identify with ultrasound alone.
A parathyroid adenoma’s blood supply is another feature. These tumors are hypervascular, meaning they have a rich network of blood vessels. Using Color Doppler ultrasound to visualize blood flow, the operator can identify a distinct feeding artery, or “polar vessel,” entering one end of the adenoma. This vessel helps confirm a suspicious mass is a parathyroid adenoma rather than a lymph node or thyroid nodule.
Distinguishing an adenoma from other neck structures requires skill. Lymph nodes can appear similar but have a fatty hilum, a central area that differs from an adenoma’s uniform appearance. While thyroid nodules are also common, a skilled operator can see that an adenoma is separate from the thyroid gland. The combination of a hypoechoic oval mass with a polar feeding vessel behind the thyroid is the classic presentation of a parathyroid adenoma.
The Ultrasound Procedure Experience
The parathyroid ultrasound process is straightforward and requires minimal preparation. There are no requirements for fasting or altering medication schedules, though you should follow any specific instructions provided by the medical facility. The examination is non-invasive and comfortable.
The scan is performed in a dimly lit room so the sonographer can see the monitor clearly. You will lie on your back on an examination table, often with a pillow placed under your shoulders to extend your neck. This position provides the best access to the area. The sonographer will apply a cool, water-based gel to your neck, which ensures a clear connection between the handheld transducer and your skin.
The sonographer will press the transducer firmly against your skin, moving it across your neck to view the glands from different angles. You should not feel pain, only slight pressure from the probe. The sonographer may ask you to swallow or turn your head to get a better view of certain areas. The procedure is completed within 20 to 30 minutes, after which the gel is wiped off, and you can return to your normal activities.
Interpreting Ultrasound Results and Subsequent Actions
After the ultrasound, a radiologist—a physician specializing in medical imaging—interprets the images. The radiologist analyzes the images for abnormalities and prepares a formal report for the ordering endocrinologist or surgeon. This report states whether a suspected parathyroid adenoma was located and describes its size, shape, and location.
The ultrasound outcome is either positive or inconclusive. A positive result means the adenoma has been clearly identified, providing the surgeon with information to plan a targeted operation. However, a scan may be inconclusive or negative. This can occur if the adenoma is very small, obscured by other structures, or in an ectopic position like the chest. An inconclusive result does not mean an adenoma is not present, only that it could not be seen with ultrasound.
If the ultrasound fails to locate the adenoma, the referring physician will order additional imaging studies. A Technetium-99 sestamibi scan is a common next step, using a radioactive tracer that is absorbed by the overactive parathyroid gland to make it visible. Another option is a 4D CT scan, which provides detailed, three-dimensional images of the neck and chest and can find adenomas not visible on other scans.