Background

The reported rate of incidental parathyroidectomy (IP) during thyroid surgery is between 5.2 and 21.6 %. Current literature reports wide discrepancy in incidence, risk factors, and outcomes. Thus study was designed to address definitively the topic of IP and identify associated risk factors and clinical outcomes with this multi-institutional study.

Methods

This retrospective cohort study included 1767 total thyroidectomies that occurred between 1995 and 2014 at two academic centers. Pathologic reports were reviewed for the presence of unintentionally removed parathyroid glands. Demographics, potential risk factors, and postoperative calcium levels were compared with matched control group. Logistic regression, t tests, and Chi squared tests were used when appropriate.

Results

IP occurred in 286 (16.2 %) of thyroidectomies. Risk factors for IP were: malignancy, neck dissection, and lymph node metastases (p = 0.005, <0.001, and <0.001). Fifty-three (19.2 %) of IPs were intrathyroidal. Those with IP were more likely to have postoperative biochemical (65.6 vs. 42.0 %; p < 0.001) and symptomatic (13.4 vs. 8.1 %; p = 0.044) hypocalcemia than controls. The number of parathyroids identified intraoperatively was inversely correlated with the number of parathyroid glands in the specimen (p < 0.001).

Conclusions

Our findings indicate that malignancy, lymph node dissection, and metastatic nodal disease are risk factors for IP. Patients with IP were more likely to have postoperative biochemical and symptomatic hypocalcemia than controls, showing that there is a physiologic consequence to IP. Additionally, intraoperative surgeon identification of parathyroid glands results in a lower incidence of IP, highlighting the importance of awareness of parathyroid anatomy during thyroid surgery.

Importance

Transoral endocrine surgery (TES) allows thyroid and parathyroid operations to be performed without leaving any visible scar on the body. Controversy regarding the value of TES remains, in part owing to the common belief that TES is only applicable to a small, select group of patients. Knowledge of the overall applicability of these procedures is essential to understand the operation, as well as to decide the amount of effort and resources that should be allocated to further study the safety, efficacy, and value of these operations.

Objective

To determine what percentage of US patients undergoing thyroid and parathyroid surgery are eligible for TES using currently accepted exclusion criteria.

Design, setting, and participants

Cross-sectional study of 1000 consecutive thyroid and parathyroid operations (with or without neck dissection) performed between July 1, 2015, and July 1, 2018, at 3 high-volume academic US thyroid- and parathyroid-focused surgical practices (2 general surgery, 1 otolaryngology-head and neck endocrine surgery). Eligibility for TES was determined by retrospectively applying previously published exclusion criteria to the cases.

Main outcomes and measures

The primary outcome was the percentage of thyroid and parathyroid cases eligible for TES. Secondary outcomes were a subgroup analysis of the percentage of specific types of cases eligible and the reasons for ineligibility.

Results

The mean (SD) age of the 1000 surgical patients was 53 (15) years, mean (SD) body mass index (calculated as weight in kilograms divided by height in meters squared) was 29 (7), and 747 (75.0%) of the patients were women. Five hundred fifty-eight (55.8%) of the patients were eligible for TES. Most patients with thyroid nodules with cytologically indeterminate behavior (165 of 217 [76.0%]), benign thyroid conditions (166 of 240 [69.2%]), and primary hyperparathyroidism (158 of 273 [57.9%]) were eligible for TES, but only 67 of 231 (29.0%) of patients with thyroid cancer were eligible. Among all 1000 cases reviewed, previous neck operation (97 of 441 [22.0%]), nonlocalized primary hyperparathyroidism (78 of 441 [17.7%]), and need for neck dissection (66 of 441 [15.0%]) were the most common reasons for ineligibility.

Conclusions and relevance

More than half of all patients undergoing thyroid and parathyroid surgery in this study were eligible for TES. This broad applicability suggests that a prospective multicenter trial is reasonable to definitively study the safety, outcomes, and cost of TES.

The newly introduced pathologic diagnosis of noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) will result in less bilateral thyroid surgery as well as deescalation in T4 suppressive and radioactive iodine treatment. Although, NIFTP is a nonmalignant lesion that has nuclear features of some papillary malignancies, the challenge for the surgeon is to identify a lesion as possibly NIFTP before the pathologic diagnosis. NIFTP, due to its reduction of overall rates of malignancy, will result in the initial surgical pendulum swinging toward lobectomy instead of initial total thyroidectomy. This American Head and Neck Society endocrine section consensus statement is intended to inform preoperative evaluation to attempt to identify those patients whose final pathology report may ultimately harbor NIFTP and can be offered a conservative surgical plan to assist in cost-effective, optimal management of patients with NIFTP.