Less experienced surgeons and removal of lymph nodes in the neck during thyroid surgery are major risk factors for accidentally damaging neighboring parathyroid glands, which can cause hypoparathyroidismshowed a large study in China.
Surgeon inexperience and a more advanced thyroid tumor also increased the risk of unintentional damage to the parathyroid gland.
These findings add to a growing number of studies that highlight a relationship between the number of thyroid surgeries performed by a surgeon each year and rates of post-surgical complications.
The study, “Analysis of risk factors for accidental parathyroid resection during thyroid surgery: a retrospective analysis of 1775 patients.”, was published in surgery today.
Thyroidectomy, surgery to remove all or part of the thyroid gland in the neck, is often recommended for thyroid tumors, which can be benign (noncancerous) or malignant (cancerous).
This type of surgery can cause complications, including unintentional damage or removal of neighboring parathyroid glands, which produce parathyroid hormone (PTH), which regulates calcium and phosphate levels in the blood.
Damage or removal of the parathyroid glands can temporarily or permanently limit the production of PTH, a condition called hypoparathyroidism. Since effective PTH replacement therapy has yet to be developed, it is “important to effectively identify and protect the parathyroid gland during operations,” the researchers wrote.
The Link of Parathyroid Removal to Hypoparathyroidism
Researchers in China investigated the effects of accidental parathyroid removal, or APR, on hypoparathyroidism and its possible risk factors. APR was classified as the detection of parathyroid gland material in surgically removed thyroid tissue after analysis.
They retrospectively analyzed data from 1,775 patients (74.7% female; mean age, 44.73 years) who underwent thyroidectomy at Union Hospital of Fujian Medical University, China, between November 2018 and October 2020.
Most (78.1%) had papillary thyroid carcinoma, the most common type of thyroid cancer, while 21.9% had benign thyroid tumors. The lymph nodes in the center of the neck closest to the thyroid were removed in all cases, as they are often the first site of cancer spread. Central and lateral neck lymph nodes were removed in 15.7% of patients.
A total of 860 surgeries (46.4%) were performed by professional surgeons, or those who perform more than 300 procedures each year, while the remaining 915 (51.6%) were performed by surgeons with less experience.
Accidental parathyroid removal occurred in 255 surgeries (14.4%), a rate similar to that reported in previous studies, the researchers noted. A higher proportion of APR surgeries were performed by less experienced surgeons than by professional surgeons (62.4% vs. 37.6%).
PTH and calcium levels before and one day, one week and six months after surgery were available for analysis only in those operated on by a professional surgeon. The data showed that the APR patients had significantly lower PTH levels than the non-APR group at all times after surgery.
A significantly higher proportion of those with APR during surgery experienced hypoparathyroidism relative to those without APR one day after surgery (80.2% vs. 39.1%), one week after surgery (47.9% vs. to 13.1%) and six months after surgery. surgery (15.6% vs 0%).
“This shows that, in addition to [APR]mechanical traction, compression, and damage to the blood supply of the parathyroid glands during the operation lead to a transient decrease in PTH,” the researchers wrote.
When the glands do not remain intact, normalization of PTH levels may take more than six months or never be achieved.
No significant differences were found between the groups for calcium levels one day and six months after surgery, which “was mainly due to the fact that patients in both groups were routinely administered [preventive] calcium supplementation after surgery,” the researchers wrote.
Lymph node removal and surgeon experience level were simultaneously identified as independent risk factors for accidental parathyroid gland removal using statistical models that considered multiple factors.
Specifically, removal of lymph nodes during surgery was associated with a 3.23-fold increased risk of PRA, and having the procedure performed by a less experienced surgeon doubled the risk.
Among patients who underwent surgery for papillary thyroid carcinoma, the lowest experience level of a surgeon was associated with an 83.7% increased risk of APR, and more advanced cancer increased the risk by 36.5%.
Professional surgeons performed surgeries in more complex cases, but removed more lymph nodes and lymph nodes invaded by cancer, suggesting a more comprehensive procedure, the analyzes showed.
As such, “despite the greater complexity of patient cases,” APR was less likely with professional surgeons than with those “with less professional experience,” the researchers wrote.
These findings show that “causes of accidental parathyroid resection are multifactorial,” the researchers wrote, adding that “predictors of APR include central lymph node dissection, [cancer] stage, and the experience of the operating surgeons.”