Important Considerations for Planning the Extent of Thyroid Surgery

How much thyroid to remove for a nodule suspicious for being cancer: total thyroidectomy, hemithyroidectomy and isthmusectomy, isthmusectomy

How much of the thyroid gland to remove (extent of thyroidectomy) is a strategic decision based on risks, benefits, and patient preferences. Key factors helping inform this decision include certainty of diagnosis of cancer, aggressiveness of the cancer, patient specific surgical risks, The standard recommendations for extent of surgery have changed over time, and there is some controversy.

Extent of thyroidectomy:

Commonly when a thyroid nodule is found to be suspicious for cancer by a needle biopsy, removing it is recommended for definitive diagnosis.  The certainty of a needle biopsy report varies from most likely benign to most likely cancerous, it is rarely 100% certain and often somewhere well within the gray zone.  Thus, surgical excision may be needed for definitive, certain diagnosis of the nodule.  Not only does the final pathologic report from surgical excision  identify whether cancer is present, and what type of cancer is present, it also can identify high risk factors such as how close the cancer was to the edge of what was removed (the margin) and the presence of aggressive features.

Sometimes, this information leads to the recommendation that the entire thyroid gland be removed.  Other times, in lower-risk situations, the opposite thyroid lobe may be safely preserved which also spares the laryngeal nerves and parathyroid glands from potential injury on the undirected side.

Therefore, a decision without complete information must be made prior to an operation for a suspicious thyroid nodule as to how much thyroid should be removed at that (initial) operation.  Is is best to remove only as much thyroid gland as is necessary to safely obtain the diagnosis?  Even if cancer is found in the final pathological assessment of a partial thyroidectomy, it may turn out that this partial thyroidectomy may be all the surgery that is needed.  Or, is it better to remove the entire thyroid at the initial procedure to avoid needing to return later to remove the rest of the thyroid gland if cancer is confirmed and if high risk features are present to support the need for complete removal of the thyroid?

Each individual situation is unique, and the available information is used for a given person’s recommendation on extent of surgery.  Ultimately, of course, an individual has the authority to determine whether to undertake a particular procedure.  But for some cases, where the advantages and disadvantages of total versus partial thyroidectomy are somewhat balanced, the following considerations may aid a person faced with this decision.

The standard thyroidectomy operations:

Possible need for thyroid hormone supplementation:

To remain in a healthy euthyroid state, a person needs thyroid hormone, whether from their own thyroid or taken as a medicine.  After all of the thyroid gland is removed, needing thyroid hormone supplementation is guaranteed.  After hemithyroidectomy and isthmusectomy, needing thyroid hormone is possible, as the remaining thyroid lobe may or may not be able to produce sufficient thyroid hormone. After isthmusectomy, needing thyroid hormone is possible, but unlikely, because the isthmus is only a small portion of the thyroid.

Risk to nearby strictures with extent of thyroid surgery:

During surgery, structures within and nearby the surgical field are at some risk of injury.  In the case of thyroid and parathyroid surgery, two special anatomical considerations are relevant: the parathyroid glands and the laryngeal nerves.

Risk to parathyroids:

Parathyroid glands have a low rate of being non-functional on the side(s) of thyroid surgery. A person needs only 1/2 of 1 parathyroid gland to have normal parathyroid function.  Both sides of the thyroid need to be operated upon and all four parathyroids need to be permanently nonfunctional to have permanent hypoparathyroidism (low parathyroid hormone).  Permanent hypoparathyroidism is estimated to occur after about 2% of total thyroidectomies (or completion thyroidectomies), and would not occur after only hemithyroidectomy.

Risk to laryngeal nerves:

Incurring a weak or paralyzed recurrent laryngeal nerve on an operated side is unlikely with thyroidectomy, estimated to occur about 2% of the time.

Operating on one side only puts only that side’s recurrent laryngeal nerve at risk.  Operating on both sides puts both recurrent laryngeal nerves at risk.  A weak or paralyzed vocal cord may recover fully, partially, or not at all.  If one vocal cord remained weak or paralyzed, and the other  side is normal, then the other side may compensate over time, with normalization of the voice and swallowing, but with partial narrowing of the airway.

If one recurrent laryngeal nerve were not functional (with an approximately 2% chance of happening):

• The voice would be breathy and weak

• The airway may be a little restricted

• Swallowing may be affected, with possible aspiration and aspiration

If both recurrent laryngeal nerves were not functional (with a less than 1% chance of happening):

• The airway would be much narrower.  This may require placement of a tracheostomy tube to maintain a safe airway.  Even if tracheostomy tube is not necessary, the smaller airway would limit physical exertion.

• The voice would be weak

• Swallowing may be affected, with possible aspiration

It is possible for thyroid cancer to invade the recurrent laryngeal nerve.  When this happens, the vocal cord on that side is usually weak prior to surgery, causing hoarseness and identifiable by looking at the vocal cords with a scope in the office before surgery.  On rare occasion, a thyroid cancer may invade into a recurrent laryngeal nerve but not cause weakness of the vocal cord.  When this happens, the nerve is at higher risk of injury during surgery, even if every effort is made to preserve the nerve.