Association for Academic SurgeryInadvertent parathyroidectomy: incidence, risk factors, and outcomes
Introduction
Thyroidectomy is performed for a variety of indications, including thyroid cancer, nodular thyroid disease with an indeterminate or nondiagnostic fine needle aspiration biopsy, a symptomatic goiter or a goiter with tracheal or esophageal impingement, substernal extension, and thyrotoxicosis. The estimated number of thyroidectomies performed yearly in the United States exceeds 92,000.1 As with any operation, challenges include minimizing complications. The major complications of thyroidectomy include recurrent laryngeal nerve injury (1.2%-7.6%),2, 3, 4 bleeding requiring reoperation (0.6%-1.6%),2, 3, 5, 6 and permanent hypoparathyroidism (1.2%-5.5%).2, 7, 8, 9, 10
The parathyroid glands can be challenging to identify intraoperatively. A parathyroid gland weighs approximately 35 mg, measures 5 mm in maximum dimension, and is usually surrounded by adipose and loose connective tissue. Parathyroid glands can become discolored with bleeding and can be mistaken for thyroid, nodal, or adipose tissue. Parathyroid glands that are subcapsular may be flattened in appearance, making them more difficult to identify and more vulnerable to removal during thyroidectomy. Parathyroid glands are often embedded with lymph nodes and can be more difficult to identify in patients with enlarged lymph nodes in the central compartment of the neck from cancer or Hashimoto's thyroiditis. Hypoparathyroidism is reported to be higher in patients undergoing thyroidectomy with central compartment neck dissection,8, 9, 11 suggesting that parathyroid glands may be more vulnerable to removal during central compartment neck dissection compared with thyroidectomy alone. Parathyroid glands may also be intrathyroidal, and their removal cannot be prevented.
Embryologically, the parathyroid glands develop from the third and fourth branchial pouches. The superior parathyroid glands arise from the fourth branchial pouch along with the lateral lobes of the thyroid gland. The inferior parathyroid glands develop from the third branchial pouch along with the thymus. The normal anatomic location of the superior parathyroid gland is fairly constant, with 80% of superior glands found near the posterior aspect of the upper thyroid lobe at the level of the cricoid cartilage where the recurrent laryngeal nerve enters the larynx posterior to the inferior pharyngeal constrictor muscle.12 It is typically posterior and superior to the recurrent laryngeal nerve, approximately 1 cm cephalad to the junction of the inferior thyroid artery and the recurrent laryngeal nerve.13 Ectopic superior glands can be found in the tracheoesophageal groove, in a paraesophageal, retroesophageal or retropharyngeal location, in the posterior mediastinum, within the carotid sheath or within the thyroid gland.14
The normal anatomic location of an inferior parathyroid gland is approximately 1 cm caudal to the junction of the inferior thyroid artery and the recurrent laryngeal nerve and anterior to the recurrent laryngeal nerve on the posterior aspect of the inferior pole of the lobe of thyroid gland.13 Because of its more extensive migration during embryologic development, an inferior parathyroid gland is more likely to be found in an ectopic location. An ectopic inferior parathyroid gland may be found in the thymus, the thyrothymic ligament, the anterior mediastinum, undescended in a submandibular location, or within the thyroid gland.14
Due to the small size and variable location of the parathyroid glands, preservation of the parathyroid glands can be a challenge during thyroidectomy. The purpose of this study was to determine the incidence of inadvertent parathyroidectomy (IP) during thyroidectomy at our institution, its risk factors and whether it is associated with the development of hypoparathyroidism.
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Materials and methods
A retrospective review of electronic medical records and a prospectively maintained database was completed for a consecutive group of patients who underwent thyroidectomy by a single surgeon from January 2010 through August 2014. The pathology reports for all study patients were reviewed to determine whether one or more parathyroid glands were unexpectedly found in the specimen submitted to pathology. During the study period, a routine protocol for processing the thyroid gland was followed at
Results
The study population consisted of 386 patients who underwent thyroidectomy, including total thyroidectomy in 241 and thyroid lobectomy and isthmusectomy in 145 patients, which was a completion thyroidectomy in 17. The mean age was 52 ± 14 y, and 327 (84.7%) patients were women. The mean and median thyroid gland weight were 69 ± 79.7 g and 38 (19, 96) g, respectively. Demographic data and clinical characteristics for the study population are presented in Table 1. Twenty-five (6.5%) patients
Discussion
Temporary hypocalcemia and permanent hypoparathyroidism have been reported in 5.4%-29.1% and 0.5%-4.7% of patients who have undergone total thyroidectomy, respectively.3, 7, 15, 16 Higher rates of permanent hypoparathyroidism have been reported in patients who have undergone total thyroidectomy in combination with central compartment neck dissection11, 17 and reoperative thyroidectomy.18, 19 Permanent hypoparathyroidism is a major complication of thyroidectomy associated with both short- and
Conclusions
In conclusion, it is important for surgeons to recognize that it is not uncommon to remove one or more parathyroid glands during thyroidectomy, and a significant percentage may be due to an intrathyroidal location. It is also important to recognize that IP is associated with a higher rate of permanent hypoparathyroidism, a complication associated with significant short- and long-term sequelae. Central compartment neck dissection is an independent and remediable risk factor for IP. Before
Acknowledgment
Authors' contributions: H.Y.Z. was involved in the design of this study, performed data collection and analysis, and was involved in the authorship of all sections of the article. J.C.H. was involved in data analysis and revision of the article. C.R.M. was involved in the design of the study, supervised the data collection and data analysis, and was involved in the authorship of all sections of the article.
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Innovations in Parathyroid Localization Imaging
2022, Surgical Oncology Clinics of North AmericaProactive exploration of inferior parathyroid gland using a novel meticulous thyrothymic ligament dissection technique
2022, European Journal of Surgical OncologyIncidental parathyroidectomy in thyroidectomy and central neck dissection
2021, Surgery (United States)Citation Excerpt :The rise in ultrasound-guided discovery of thyroid nodules and thyroidectomies suggests this issue to be of growing consequence.7-9 Adjuncts such as loupe magnification, autofluorescence, and frozen section have become more pervasive, but studies across time suggest no parallel decline in rates.2 Isolated removal of a single parathyroid may confer no ill effects, as the remaining 3 organs often compensate.
Impact of incidental parathyroidectomy and mediastinal-recurrent cellular and lymph-node dissection on parathyroid function after total thyroidectomy
2020, Annales Francaises d'Oto-Rhino-Laryngologie et de Pathologie Cervico-FacialeImpact of incidental parathyroidectomy and mediastinal-recurrent cellular and lymph-node dissection on parathyroid function after total thyroidectomy
2020, European Annals of Otorhinolaryngology, Head and Neck DiseasesCitation Excerpt :The macroscopic resemblance of parathyroid glands to lymph nodes, the wide variations in parathyroid gland location and especially parathyroid glands inside the cellular and lymph-node resection tissue in monobloc mediastinal-recurrent dissection, and parathyroid glands in fatty involution may all cause confusion in surgery and a risk of unintentional parathyroidectomy. It seems intuitively obvious that associating mediastinal-recurrent cellular and nodal dissection to total thyroidectomy is going to increase the risk of incidental parathyroidectomy [10–17]. The same is true for definitive pathology examination of the surgical specimen [12,18,19], as thyroid cancer discovered before or during surgery leads to mediastinal-recurrent dissection, increasing the risk of incidental parathyroidectomy.
Surgical Hypoparathyroidism
2018, Endocrinology and Metabolism Clinics of North AmericaCitation Excerpt :The surgeon should use judgment about the extent of resection in multigland hyperplasia; typically, a remnant smaller than 50 mg is left in place after subtotal resection. Inadvertent parathyroidectomy during thyroid surgery is a potentially remediable risk factor for surgical hypoparathyroidism that occurs in up to 20% of patients undergoing thyroidectomy,42 and in up to 28% of patients undergoing total thyroidectomy with central neck dissection.43 Therefore, after resection all thyroid specimens should be promptly examined in the operating room and before sending them to pathology to facilitate autotransplantation should a normal parathyroid gland have been inadvertently removed.