ABSTRACT

Objective:

Hypocalcemia remains a common problem after thyroidectomy. One of the most common causes of this condition is incidental parathyroidectomy. This study aimed to evaluate the risk factors for incidental parathyroidectomy and the clinical outcomes of incidental parathyroidectomy in patients undergoing thyroidectomy.

Methods:

A retrospective analysis was conducted on 817 patients who underwent thyroidectomy at the Department of General Surgery at Gazi University between January 2015 and June 2022. Medical records were reviewed for demographic, pathological, and clinical variables. The primary outcome measure was the factors affecting incidental parathyroidectomy, and the secondary outcome measure was the clinical results of incidental parathyroidectomy.

Results:

Adding lymph node dissection to thyroidectomy statistically increased the frequency of incidental parathyroidectomy (p<0.001). The incidence of incidental parathyroidectomy was significantly higher in patients whose final diagnosis was malignant (p=0.006). Considering some characteristics of the malignant group, extrathyroidal spread, lymphatic invasion, vascular invasion, and positive surgical margins were not statistically significant for incidental parathyroidectomy. Post-operative calcium levels were statistically significantly lower in the incidental parathyroidectomy group (p<0.001). The incidental parathyroidectomy group had a significantly higher incidence of post-operative biochemical hypocalcemia (calcium level <8.5 mg/dL) (p<0.001).

Conclusion:

Incidental parathyroidectomy may occur during total thyroidectomies. This situation increases with thyroidectomies performed for malignant reasons and lymph node dissection. Moreover, although incidental parathyroidectomy causes postoperative biochemical hypocalcemia, its effect on symptomatic hypocalcemia is low.

INTRODUCTION

Thyroid cancers have been detected more frequently in recent years with the development of ultrasonography. The recommended treatment modality for thyroid cancer is thyroidectomy (1). Although post-operative hypocalcemia has decreased with the development of surgical techniques, it is still a complication that can be seen between 16-55% in patients undergoing thyroidectomy (2,3). In most cases, post-operative hypocalcemia is transient and asymptomatic and is detected only biochemically. However, in a limited number of patients, this condition may be permanent and may require lifelong oral calcium supplementation.

An incidental parathyroidectomy may occur even in an experienced surgeon. There is no consensus on the incidence of incidental parathyroidectomy, its risk factors, and whether it leads to biochemical or symptomatic hypocalcemia (2,4-7). In many previous studies focusing on this issue, different types of surgery have been included (8-10). However, studies on the risk factors and outcomes of incidental parathyroidectomy only during total thyroidectomy are limited. The aim of this study was to determine the risk factors that increase the incidence of incidental parathyroidectomy during total thyroidectomy and the clinical effects of incidental parathyroidectomy.

MATERIALS AND METHODS

In this study, a retrospective analysis was conducted on 817 patients who underwent thyroidectomy at the Department of General Surgery at Gazi University between January 2015 and June 2022. The study protocol was approved by the Gazi University Institutional Ethics Board (approval number: 15, date: 05.09.2023). Medical records were reviewed for demographic, pathological, and clinical variables. The primary outcome measure was the factors affecting incidental parathyroidectomy, and the secondary outcome measure was the clinical results of incidental parathyroidectomy.

Statistical Analysis

The data from the study were analyzed using SPSS version 23.0. Initially, descriptive statistics were used. Categorical variables are presented as numbers and percentages, while continuous variables are represented as either mean ± standard deviation or median (interquartile range). Continuous variables were assessed for normal distribution using both visual methods (histogram and probability graphs) and analytical techniques (Kolmogorov-Smirnov/Shapiro-Wilk tests). Differences in continuous variables were analyzed using the Mann-Whitney U test, whereas categorical variables were analyzed using chi-square tests. P<0.05 was considered statistically significant.

RESULTS

The study included 817 patients who underwent total thyroidectomy at our institution between January 2015 and June 2022. The mean age of the patients was 49.9±12.2 years. Of the patients included in the study, 638 (78.1%) were female and 179 (34.8%) were male. The median nodule size of the patients was 2.0 (1.2- 3.0) cm. Total thyroidectomy was performed in 684 patients (83.7%), total thyroidectomy and central lymph node dissection in 116 patients (14.2%), and total thyroidectomy and neck dissection in 17 patients (2.1%). Post-operative histopathological examination revealed that 452 (55.3%) patients had benign lesions and 365 (44.7%) had malignant lesions. Of the 817 patients who underwent thyroidectomy, 265 (32.4%) underwent lymph node dissection and 158 (19.3%) underwent parathyroidectomy. The median pre-operative calcium level was 9.6 (9.3-9.9) mg/dL and the median post-operative calcium level as 9.3 (8.8-9.7) mg/dL (Table 1).

Table 1

Table 2 shows a comparison of the frequency of incidental parathyroidectomy according to the descriptive characteristics of the patients. There was no statistically significant difference between the groups of patients with and without incidental parathyroidectomy in terms of age, sex, and nodule size. The incidence of incidental parathyroidectomy was statistically significant according to the surgery performed (p<0.001). The incidence of incidental parathyroidectomy was significantly higher in patients whose final diagnosis was malignant (p=0.006) and those who underwent lymph node dissection (p<0.001). Considering some characteristics of the malignant group, extrathyroidal spread, lymphatic invasion, vascular invasion, and positive surgical margins were not statistically significant for incidental parathyroidectomy.

Table 2

DISCUSSION

Previous studies have shown that the incidence of incidental parathyroidectomy in thyroid surgery depends on the surgical procedure performed (5-7). However, the number of studies focusing on incidental parathyroidectomy in total thyroidectomy is limited. Manouras et al. (5) reported an incidence of incidental parathyroidectomy of 19.7% in patients undergoing total thyroidectomy. In the study by Du et al. (11), this rate was 10.3%. Manatakis et al. (2) reported an incidental parathyroidectomy rate of 24.9%. In our study, similar to previous studies, we determined the frequency of incidental parathyroidectomy in total thyroidectomies to be 19.3%.

Studies have identified several potential risk factors for incidental parathyroidectomy. Youssef et al. (12) showed that the addition of simultaneous central lymph node dissection to thyroidectomy increased the risk of incidental parathyroidectomy. Sippel et al. (13) reported that younger age, malignant pathology, and bilateral thyroid resection were risk factors for incidental parathyroidectomy. Du et al. (11) reported lateral cervical lymph node dissection, Song et al. (14) reported nodule size, and Khairy and Al-Saif (10) found that extrathyroidal tumor spread was a risk factor for incidental parathyroidectomy. In the present study, we found that the addition of lymph node dissection to total thyroidectomy or lymph node detection on histopathological examination and malignant pathology were risk factors for incidental parathyroidectomy. However, age, sex, nodule size, extrathyroidal spread, and positive surgical margin were not evaluated as risk factors for incidental parathyroidectomy.

The frequency of biochemical hypocalcemia after thyroidectomy varies between 5 % and 55% in the literature (6,11,15,16). In our study, the frequency was recorded as 14.3%. In our study, we also showed that incidental parathyroidectomy decreased post-operative calcium levels and significantly increased biochemical hypocalcemia. However, consistent with previous studies, we did not detect a significant increase in the frequency of symptomatic hypocalcemia and permanent hypocalcemia in patients who underwent incidental parathyroidectomy (6,11). We believe that this is because the remaining parathyroid glands continue to meet physiological needs, similar to other authors.

Study Limitations

The limitation of our study is that it is retrospective in nature.

CONCLUSION

In conclusion, incidental parathyroidectomy may occur during total thyroidectomies. This situation increases with thyroidectomies performed for malignant reasons and lymph node dissection. Moreover, although incidental parathyroidectomy causes post-operative biochemical hypocalcemia, its effect on symptomatic hypocalcemia is low.

Ethics

Ethics Committee Approval: The study protocol was approved by the Gazi University Institutional Ethics Board (approval number: 15, date: 05.09.2023).

Informed Consent: Retrospective study.

Peer-Review: Externally peer-reviewed.

Authorship Contributions

Concept: Ç.B., Design: Ç.B., H.B., Supervision: K.D., H.B., Resources: H.B., Materials: A.Y., Data Collection or Processing: Ç.B., A.Y., Analysis or Interpretation: K.D., H.B., Literature Search: Ç.B., Writing: H.B.

Conflict of Interest: No conflict of interest was declared by the authors.

Financial Disclosure: The authors declared that this study received no financial support.

References

1Yip L, Sosa JA. Molecular-Directed Treatment of Differentiated Thyroid Cancer: Advances in Diagnosis and Treatment. JAMA Surg 2016; 151: 663-70.

2Manatakis DK, Balalis D, Soulou VN, Korkolis DP, Plataniotis G, Gontikakis E. Incidental Parathyroidectomy during Total Thyroidectomy: Risk Factors and Consequences. Int J Endocrinol 2016; 2016: 7825305.

3Nellis JC, Tufano RP, Gourin CG. Association between Magnesium Disorders and Hypocalcemia following Thyroidectomy. Otolaryngol Head Neck Surg 2016; 155: 402-10.

4Applewhite MK, White MG, Xiong M, Pasternak JD, Abdulrasool L, Ogawa L, et al. Incidence, Risk Factors, and Clinical Outcomes of Incidental Parathyroidectomy During Thyroid Surgery. Ann Surg Oncol 2016; 23: 4310-5.

5Manouras A, Markogiannakis H, Lagoudianakis E, Antonakis P, Genetzakis M, Papadima A, et al. Unintentional parathyroidectomy during total thyroidectomy. Head Neck 2008; 30: 497-502.

6Sasson AR, Pingpank JF Jr, Wetherington RW, Hanlon AL, Ridge JA. Incidental parathyroidectomy during thyroid surgery does not cause transient symptomatic hypocalcemia. Arch Otolaryngol Head Neck Surg 2001; 127: 304-8.

7Lee NJ, Blakey JD, Bhuta S, Calcaterra TC. Unintentional parathyroidectomy during thyroidectomy. Laryngoscope 1999; 109: 1238-40.

8Özden S, Erdoğan A, Simsek B, Saylam B, Yıldız B, Tez M. Clinical course of incidental parathyroidectomy: Single center experience. Auris Nasus Larynx 2018; 45: 574-7.

9Sakorafas GH, Stafyla V, Bramis C, Kotsifopoulos N, Kolettis T, Kassaras G. Incidental parathyroidectomy during thyroid surgery: an underappreciated complication of thyroidectomy. World J Surg 2005; 29: 1539-43.

10Khairy GA, Al-Saif A. Incidental parathyroidectomy during thyroid resection: incidence, risk factors, and outcome. Ann Saudi Med 2011; 31: 274-8.

11Du W, Fang Q, Zhang X, Cui M, Zhao M, Lou W. Unintentional parathyroidectomy during total thyroidectomy surgery: A single surgeon’s experience. Medicine (Baltimore) 2017; 96: e6411.

12Youssef T, Gaballah G, Abd-Elaal E, El-Dosoky E. Assessment of risk factors of incidental parathyroidectomy during thyroid surgery: a prospective study. Int J Surg 2010; 8: 207-11.

13Sippel RS, Ozgül O, Hartig GK, Mack EA, Chen H. Risks and consequences of incidental parathyroidectomy during thyroid resection. ANZ J Surg 2007; 77: 33-6.

14Song CM, Jung JH, Ji YB, Min HJ, Ahn YH, Tae K. Relationship between hypoparathyroidism and the number of parathyroid glands preserved during thyroidectomy. World J Surg Oncol 2014; 12: 200.

15Shaha AR, Jaffe BM. Parathyroid preservation during thyroid surgery. Am J Otolaryngol 1998; 19: 113-7.

16Pattou F, Combemale F, Fabre S, Carnaille B, Decoulx M, Wemeau JL, et al. Hypocalcemia following thyroid surgery: incidence and prediction of outcome. World J Surg 1998; 22: 718-24.

Evaluation of risk factors for incidental parathyroidectomy during thyroidectomy