Posts

How Surgeons Decide Which Parathyroid Glands to Remove

/in /by

Once a decision for surgery has been made and the surgeon has selected the desired imaging prior to the surgery, what actually takes place during the operation? How does the surgeon determine which gland or glands are abnormal?

The answers to these questions are not quite as straightforward or consistent among surgeons as one might expect. There are a variety of gland characteristics that a surgeon can rely on to decide which glands to remove. These characteristics include:

  1. The findings on preoperative imaging
  2. The shape, size, and color of the individual glands
  3. Comparison of the four glands during the surgery
  4. Measurement of PTH drop following removal of one or more glands
  5. Pathologic assessment of the gland, either by frozen section (available during the surgery, but adds time) or permanent section (only available a few days after)

In practice, these five inputs tend to sort surgeons into two broad philosophies.

Philosophy 1: Trust the imaging, find the one gland

Some surgeons rely heavily on preoperative imaging to decide if they can select a single gland to locate and remove. These surgeons typically will not recommend surgery unless at least one, and preferably two, preoperative imaging tests point to a single gland as the culprit. Given this selectivity, the operation is focused on finding only one gland presumed to be abnormal.

Once it’s identified, the surgeon typically uses intraoperative PTH measurement to see if the level has dropped. If it hasn’t dropped enough, the operation is extended to look for the other glands, with PTH rechecked after any additional glands are removed until the level falls sufficiently.

Some surgeons in this camp also send every removed gland for frozen section to confirm it’s parathyroid tissue and to get the pathologist’s estimate of “hypercellularity.” That said, there’s no real consensus on whether hypercellularity correlates with PTH overproduction, so it’s debatable how useful that feedback actually is, and sometimes the pathologist can’t even confirm the tissue is parathyroid gland from the frozen section alone.

The tradeoff: if the preoperative imaging is accurate and the PTH level drops sufficiently, this can be the least invasive approach. But imaging can localize one abnormal gland while missing a second one that doesn’t show up and the PTH value might still drop enough to look like a cure even though an abnormal gland remains. Those patients sometimes aren’t discovered to have persistent hyperparathyroidism until lab work at six months shows the calcium is still high. And if the PTH doesn’t drop after the single gland comes out, relying on intraoperative measurements can significantly prolong the surgery, since each result takes about 20–30 minutes to come back.

There’s also a judgment call baked into this approach: what PTH level counts as evidence of cure? Historically, surgeons have accepted a level that’s 50% or less of the preoperative value but that criterion can be misleading, especially when the starting PTH was very high.

Philosophy 2: Find all four glands, every time

Other surgeons choose to identify all four glands at the initial operation regardless of what the preoperative imaging showed. The imaging becomes a roadmap rather than a limit; the surgeon incorporates it with what’s actually seen at surgery. The glands flagged by sestamibi scan, ultrasound, or other imaging are expected to appear abnormal and are removed; the remaining glands are exposed to confirm they look normal, or “dormant.”

Some patients have what’s called four-gland hyperplasia, where all four glands are contributing to the hyperparathyroidism to varying degrees. In these patients, all four glands may look similar,  each with some abnormality, but not necessarily large. Here the surgeon must identify the most normal-appearing gland, leave a portion of it in place, and remove the other three completely.

Intraoperative PTH measurement isn’t routinely needed with this approach, since it’s a safe assumption that identifying and removing the abnormal gland(s) from all four will cure the patient. PTH is simply checked later, in recovery or at a follow-up visit.

The tradeoff: this approach doesn’t depend on positive preoperative imaging and skips the extra operating-room time for intraoperative PTH. But it’s more invasive, since dissection extends to all four glands, which raises the incidence of temporary hypocalcemia (and, rarely, prolonged or permanent hypocalcemia if the “normal” glands’ blood supply is compromised during dissection). More extensive dissection also means a higher chance of temporary hoarseness after surgery, though this is almost always transient.

Neither approach is simply right

Both philosophies are defensible, and the best surgeons choose deliberately based on the quality of their imaging, their patient population, and how much operative time they’re willing to spend chasing a PTH number. But deciding on a philosophy is only the first challenge. Once you’re actually in the neck, you still have to answer a much more concrete question: what does an abnormal gland actually look like? That’s the subject of the next post in this series.

How Surgeons Identify an Abnormal Parathyroid Gland

/in /by

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.