The relationship between thyroidectomy complications and body mass index

Obesity is a growing public health problem associated with many comorbid diseases. The number of patients with a high body mass index (BMI) undergoing surgical procedures increases with the increasing obesity rate. Considering endocrine surgery, several studies have reported the relationship between obesity and thyroid cancer or hyperparathyroidism. There are scarce studies reporting the safety and complications of endocrine surgery in high body mass index patients1-7. The aim of this study was to evaluate the SUMMARY


INTRODUCTION
Obesity is a growing public health problem associated with many comorbid diseases. The number of patients with a high body mass index (BMI) undergoing surgical procedures increases with the increasing obesity rate. Considering endocrine surgery, several studies have reported the relationship between obesity and thyroid cancer or hyperparathyroidism. There are scarce studies reporting the safety and complications of endocrine surgery in high body mass index patients 1-7 . The aim of this study was to evaluate the

Statistical Analysis
The 25 th version of the "Statistics Package for Social Sciences" by International Business Machines Corporation (IBM) (New York, United States) was utilized for statistical analysis. Fisher's exact t-test was used for comparing discrete variables and one-way ANOVA was used for continuous variables. Logistic regression was used for multivariate analysis. A p-value of less than 0.05 was considered statistically significant.

RESULTS
A total of 145 patients were enrolled. One hundred twenty-five were female (86.2%) and 20 were male (13.8%). There were 66 patients (45.5%) in the BMI <25 group and 79 patients (54.5%) in the BMI≥ 25 group. The mean age in the BMI <25 group was 43.9 (17-73) years and the mean age in the BMI≥ 25 group was 48.2 (24-74) years. In the BMI <25 group, 5 (7.5%) patients were male and 61 (92.5%) were female. In the BMI≥ 25 group, 15 (19%) patients were male and 64 (81%) were female. There was no statistically significant difference between the two groups in terms of age (p=0.330) and gender (p=0.055). No surgical site infection and postoperative hematoma/bleeding complications were observed in any patients in both groups.
When both groups were compared in terms of operative time, the mean operative time was 148.4 minutes (90-235) in the BMI <25 group and 153.4 minutes (85-285) in the BMI≥ 25 group (p=0.399).
In the BMI <25 group, 25 (37.9%) patients had transient hypocalcemia postoperatively, whereas in the BMI≥ 25 group, 23 (29.1%) patients had transient hypocalcemia (p = 0.291). Permanent hypocalcemia was not observed in any patient in the BMI <25 group; in the BMI≥ 25 group, it was observed only in 2 patients (2.5%) (p = 0.501). There were no statistically significant differences between the two groups in terms of postoperative transient and permanent hypocalcemia rates.
Transient recurrent nerve palsy was observed in 1 (1.5%) patient in the BMI <25 group and in 3 (3.8%) patients in the BMI≥ 25 group. None of the patients had permanent recurrent nerve palsy. there was no statistically significant difference between the two groups in terms of postoperative recurrent nerve palsy (p=0.626).
In the BMI <25 group, parathyroid autotransplantation was performed on 1 patient (1.5%); in the BMI≥ 25 group, it was performed on 7 (8.9%) patients. Although relationship between body mass index and thyroidectomy complications including parathyroid autotransplantation rates among other parameters in other studies.

METHODS
Patients who underwent total thyroidectomy in our center between January 2015 and December 2018 were enrolled in this study. Patients who underwent thyroidectomy for recurrence, hemithyroidectomy, completion thyroidectomy, parathyroidectomy, and lymph node dissection were excluded. Neuromonitoring is not a routine practice in our center due to technical and financial reasons. The cases operated with neuromonitoring were also excluded from the study. All operations were performed by two surgeons. The surgical technique involved conventional standard ligation (clamping-tie) and vascular closure devices for hemostasis. Parathyroid glands were identified and dissected within their capsules maintaining vascularization as much as possible. The recurrent nerve was always identified at the laryngeal penetration point. Parathyroid autotransplantation into the sternocleidomastoid muscle or strap muscles was used as a salvage procedure in case of the devascularization of the glands.
Patients were divided into two groups, BMI <25 and BMI≥ 25. Demographics, American Society of Anesthesiologists (ASA) scores, operation time (minutes), postoperative bleeding complications, parathyroid autotransplantation rates, surgical site infection, postoperative serum calcium level, postoperative recurrent nerve palsy, and length of stay were recorded and retrospectively analyzed.
Hypocalcemia was defined as a postoperative serum calcium level below 8 mg/dl. Hypocalcemia lasting less than 6 months was defined as transient, and lasting more than 6 months was defined as permanent.
Recurrent nerve palsy was diagnosed with indirect laryngoscopy which was performed on patients with dysphonia, dyspnea, and swallowing disorders. Recurrent laryngeal nerve palsy that was persistent for 6 months and documented by laryngoscopy was considered as permanent palsy.
Approval from the institutional research ethics board was obtained (decision number 2019/12-2). the ratio seems higher in the BMI≥ 25 group, there was no statistically significant difference between the two groups in terms of performing parathyroid autotransplantation (p=0.055) No statistically significant difference was found between the two groups in terms of any parameter examined both with univariate and multivariate analyses.
not prolong the hospital admission and required reoperation. They concluded that thyroidectomy and parathyroidectomy can be performed safely in this patient group with appropriate surgical decision making. Our study found no wound site infections with a smaller patient group.
Our study found no statistically significant difference between patients with normal and high BMI in terms of wound site infection, hematoma, transient or permanent hypocalcemia, or recurrent nerve injury. Finel et al. 5 reported similar results about complications but prolonged surgery in patients with a high BMI. They attributed this difference to bad exposure due to shorter and wider neck, and harder dissection of the parathyroid tissue in adipose tissue in this patient group.
Milone et al. 6 also reported similar findings and longer duration of operation in patients with BMI≥ 25 in their series of 266 patients with similar comments about anatomy and patient positioning. The harder dissection of the parathyroid tissue in the adipose tissue can also result in a devascularization of the parathyroid glands. We, therefore, included the need for parathyroid autotransplantation to our variables and found a higher rate (1.5% vs 8.9%) in patients with a high BMI. However, the difference was not statistically significant and did not result in a longer operative time.
Hypocalcemia, either temporary or permanent, is a common and important problem after thyroidectomy. Current metanalyses report a rate of 19%-38% transient and 0%-3% permanent hypocalcemia after thyroidectomy 8 . Our study revealed similar rates in both groups with no increase in patients with a high BMI.
Recurrent nerve palsy is one of the most serious complications of thyroidectomy. Current literature reveals a rate of 9.8% (1.4%-38.4%) transient and 2.3% (0%-18.6%) permanent recurrent nerve palsy after thyroidectomy 9 . Our study found similar rates for temporary injury and no cases of permanent ones. The latest paper about obesity and thyroidectomy was published in 2019 by Farag et al. 7 and it also reports no relationship between obesity and thyroidectomy complications. Our study found similar results with previous reports. The retrospective design and number of patients are limitations of our study.

CONCLUSION
We think there is no relationship between a high BMI and thyroidectomy complications, and surgery can also be performed safely in this patient group.

DISCUSSION
The increasing prevalence of obesity also brings an increase in the number of patients with a high body mass index undergoing general surgical procedures. This led us to investigate the relationship between complications of general surgical procedures and a high body mass index.
Thyroidectomy is one of the most common general surgical procedures. Buerba et al. 4 reported an increased rate of wound site complications in obese and morbidly obese patients, and also urinary complications in morbidly obese patients in their study of 26864 patients. The same study showed the relationship between obesity and wound site complications and longer durations of surgery after parathyroidectomy. The authors noted that despite the statistical significance, the difference might not be clinically significant as the complications were rare, they did Multicenter prospective studies and metanalyses can increase knowledge in the subject.

Financial Disclosure
The authors declare that this study has received no financial support.

Conflicts of Interest
No conflict of interest was declared by any of the authors.