How Surgeons Identify an Abnormal Parathyroid Gland
It is extremely important to understand that we do not need imaging to make a diagnosis of primary hyperparathyroidism. The diagnosis is based on the laboratory findings.
Sometimes those findings are very clear, and sometimes they fall into a gray zone.
If the calcium is repeatedly high and the parathyroid hormone level is elevated—or even “normal” when it should be suppressed—primary hyperparathyroidism is usually the explanation. If the calcium is high and the PTH is appropriately suppressed, then the explanation for the high calcium lies elsewhere.
Borderline situations do occur. If the calcium is only high-normal, or the PTH is only modestly elevated, additional laboratory evaluation may be necessary before the diagnosis is certain. There are also uncommon conditions that can mimic primary hyperparathyroidism, so the lab results always need to be interpreted in the context of the whole patient.
This series addresses the situation in which the diagnosis has already been confirmed.
I have written other posts about when surgery should be recommended, but in most cases surgery should at least be considered once the diagnosis is certain based on the lab work. Some physicians still reserve the decision about surgery until after imaging is performed. That is not the ideal way to think about it.
Once the diagnosis is confirmed biochemically, there is abnormal parathyroid function somewhere. The remaining question is which gland—or glands—is responsible.
That distinction is important because imaging does not tell us whether the patient has hyperparathyroidism. It helps us localize the abnormal gland or glands after the diagnosis has already been made.
In this series, I will look at the different ways we try to identify the abnormal gland or glands, including:
- sestamibi scanning
- ultrasound of the neck
- 4D CT scanning
- choline PET imaging
- intraoperative use of the unique autofluorescence characteristics of parathyroid tissue
- visual assessment of the glands during surgery
- pathology findings
- intraoperative functional testing
Each of these provides useful information, but none of them tells the whole story by itself.
Parathyroid surgery came before modern imaging
Surgery for hyperparathyroidism has a long history. The first generally recognized successful parathyroidectomy for primary hyperparathyroidism was performed by Felix Mandl in Vienna in 1925.
At that time, surgeons had none of the imaging studies we use today. They also could not measure intact PTH levels.
They relied heavily on the clinical picture, serum and urinary calcium measurements, skeletal findings, and exclusion of other causes of hypercalcemia.
Without a PTH level, it was much more important to consider all of the other possible explanations for high calcium before proceeding to surgery. That kind of exhaustive work-up is much less commonly necessary today because modern intact PTH testing allows us to determine whether the parathyroid glands are responding appropriately to the calcium level.
Once the surgeon was confident in the diagnosis, the traditional operation was a bilateral neck exploration. The surgeon would identify all four parathyroid glands and visually decide which gland—or glands—appeared abnormal.
Surgeons relied heavily on the size, color, shape, and appearance of the glands, often supplemented by pathology to confirm that tissue removed was parathyroid tissue.
Large cervical incisions were already routine for thyroid surgery, which made up much of neck surgery at the time, so parathyroid operations were generally performed through a similar exposure.
Fortunately, much of that is now history.
Modern localization studies have allowed surgeons to plan much more focused operations in many patients. But they have also created a new source of confusion: patients and even physicians sometimes begin to think that the scan makes the diagnosis.
It does not.
The lab work makes the diagnosis. The imaging helps us decide where to look.
In Part Two, I will review the preoperative imaging studies available today and explain what each one can—and cannot—tell us about which parathyroid gland is abnormal. Not all surgeons use these studies in the same way, and a positive or negative scan does not always mean what patients assume it means.
Disclaimer
This article is for general education only and is not personal medical advice. Individual recommendations depend on a patient’s history, laboratory findings, imaging, operative findings, and overall clinical situation.
