Thyroidectomy in Cats

Thyroidectomy is a surgical procedure which involves removing one or both thyroid glands. Thyroidectomy is used to treat hyperthyroidism, a common condition in older cats in which the thyroid glands produce extra amounts of thyroid hormones. Thyroidectomy is also used to treat select cases of thyroid cancer. The surgery has a high success rate, although postoperative complications are possible.

There are a few different surgical techniques veterinary surgeons can use to remove the thyroid gland(s). The technique used will depend on whether or not both glands need to be removed. The procedure steps for both single (unilateral) thyroid removal and total (bilateral) thyroid removal will be discussed below. These techniques carry the lowest risk of complication and the highest rate of success.

Preoperative Preparations

1. For a few weeks prior to surgery, cats will be required to take oral medications to help them gain weight, lower their heart rate, and prepare them for the general anesthetic.
2. The surgeon may take blood tests prior to surgery to confirm kidney function.
3. The cat will first be anesthetized.

Unilateral Thyroidectomy

1. The surgeon will make the initial entry incision and identify the enlarged thyroid or tumor.
2. The thyroid capsule is then cut, and the surgeon will take care to avoid damaging the parathyroid gland.
3. The external parathyroid gland and surrounding thyroid capsule will then be dissected, or separated, from the tumor.
4. The blood supply to the tumor will be cut off using bipolar cautery.
5. Once the blood supply has been ligated, the tumor will be removed along with the surrounding thyroid capsule.
6. The thyroid capsule surrounding the parathyroid gland will be left in place to ensure proper blood flow and prevent complications from parathyroid damage.
7. The surgeon will ensure all diseased portions of the thyroid have been removed before suturing the wound closed with absorbable sutures.
8. The initial entry site will then be sutured.

Bilateral Thyroidectomy

1. The surgeon will repeat the steps listed above to remove the other thyroid gland.
2. Some surgeons may suggest that the removal of the second thyroid gland take place three to four weeks following the removal of the first. However, this is may not be ideal, particularly because the disease is more common in older cats that are susceptible to complications associated with general anesthesia.

The efficacy of the surgical procedure will depend on the underlying condition. While there are some valid concerns about administering general anesthesia to older cats, the surgery is short and typically cures hyperthyroidism in the majority of cats. For cases of thyroid cancer, the prognosis is usually guarded due to the condition of the heart at the time of surgery.

Owners should ensure that cats rest during the recovery period and drink plenty of water. Cats that have undergone thyroidectomy will usually be prescribed anti-inflammatory medications and analgesics for pain management. Cats may be required to wear an Elizabethan collar to prevent them from irritating the surgery site. Owners should check the surgery site daily to ensure no bleeding, pus, or swelling has developed. Follow-up appointments will typically be scheduled for a few days following surgery, and again two to three weeks following surgery to monitor healing and remove sutures.

The cost of thyroidectomy will vary based on other costs incurred, such as medications and supportive care. The cost of thyroidectomy on its own can range from $900 to $1,200.

Though the surgery is generally curative in most cases, complications after surgery are possible. If one thyroid gland is removed, the other thyroid gland may become diseased over time and will also have to be removed. The condition may recur in the same thyroid gland because a small amount of thyroid capsule tissue is not removed. In some cases, surgery reveals problems with kidney function, which is why surgeons will generally attempt to assess kidney function prior to surgery. 

There is also a chance that thyroidectomy will cause damage to the parathyroid gland. This can cause calcium levels to drop, which can lead to serious complications such as tremors and seizures. Damage to the parathyroid gland is generally managed with calcium and vitamin D supplementation, which is usually successful. For cases of thyroid cancer, there is a chance that the condition can recur following surgery.

Hyperthyroidism has been linked to pollutants in the environment, such as:

• BPA: A chemical used to make certain plastics
• PBDE: A flame-retardant chemical used in foam and plastics
• Soy isoflavones: A plant derivative often found in commercial cat food 

Owners are encouraged not to use plastic food or water bowls as these may contain toxic chemicals known to cause hyperthyroidism. Certain cat litter may also contain harmful chemicals that cause hyperthyroidism. Fish-based commercial diets may also play a role in the development of hyperthyroidism. Diets that are also incredibly low or high in iodine should be avoided.