Association for Academic Surgery
Inadvertent parathyroidectomy: incidence, risk factors, and outcomes

https://doi.org/10.1016/j.jss.2016.06.019Get rights and content

Abstract

Background

Parathyroid glands are ≤5 mm, often subcapsular or intrathyroidal, and obscured by lymph nodes, making preservation a challenge. The purpose of this study was to determine the incidence of inadvertent parathyroidectomy (IP) and whether it contributes to hypoparathyroidism after thyroidectomy.

Materials and methods

A retrospective review of all thyroidectomies by a single surgeon from January 2010 to August 2014 was completed to determine the rate of IP and permanent hypoparathyroidism. Medical records were assessed for demographics, extent of thyroidectomy, central compartment neck dissection, thyroid gland weight, parathyroid autotransplantation, reoperation, pathology, postoperative calcium levels, and number of parathyroid glands removed.

Results

A total of 386 patients underwent thyroidectomy. Mean age was 52 y, and 327 (85%) patients were women. There were 25 (7%) patients who underwent reoperation, 40 (10%) who underwent central compartment neck dissection, and 128 (33%) who underwent parathyroid autotransplantation. IP occurred in 78 (20%) patients. Permanent hypoparathyroidism occurred in 7 (2.7%) of 258 patients after total or completion thyroidectomy, four (6.7%) with IP compared with three (1.5%) without IP (P = 0.033). Logistic regression analysis revealed that female gender (odds ratio = 2.768, P = 0.040), central compartment neck dissection (odds ratio = 9.584, P = 0.001), and thyroid gland weight (odds ratio = 0.994, P = 0.022) were independent factors associated with IP.

Conclusions

IP, which occurred in 20% of patients undergoing thyroidectomy, is a potentially remediable factor associated with a higher rate of hypoparathyroidism. Central compartment neck dissection is an independent risk factor for IP.

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.

Section snippets

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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