Surgical outcomes and complications of completion thyroidectomy: a retrospective study

Abstract

This study aims to evaluate the surgical outcomes and complications of completion thyroidectomy (CT) in patients who previously underwent lobectomy with istmhectomy (LI) or subtotal thyroidectomy (ST). The study also seeks to identify patient groups that benefit from CT and examine the risks associated with this procedure. A retrospective analysis was conducted on 70 patients who underwent completion thyroidectomy in our General Surgery Clinic between January 2015 and July 2023. Patients who had previously undergone thyroid surgery due to thyroid malignancy or benign goiter were included in the study. Demographic data, initial pathology, surgical procedures, postoperative complications, and histopathological findings were analyzed. Postoperative complications, including hypoparathyroidism, recurrent laryngeal nerve injury, hematoma, and the need for tracheostomy, were recorded and compared between groups. Based on prior surgical history, 18 patients (25.7%) had previously undergone LI, while 52 patients (74.3%) had undergone subtotal thyroidectomy (ST). The overall complication rate was significantly higher in the ST group (36.5%) compared to the LI group (11%) (p = 0.04). A significant association was found between larger nodule size and higher complication rates (p = 0.03). Postoperative histopathological examination revealed malignancy in 18.5% of patients, with no significant difference between the groups in terms of histopathological findings. This study highlights the increased risk of complications, particularly hypoparathyroidism and recurrent laryngeal nerve injury, in patients undergoing completion thyroidectomy after subtotal thyroidectomy. However, no significant differences were found between the groups regarding malignancy rates and histopathological findings. Further studies with larger patient populations and long-term follow-ups are needed to better understand the clinical benefits and risks of CT.

Introduction

The thyroid gland, composed of two anatomically connected lobes, is among the largest endocrine organs in the human body, typically weighing between 20 and 30 g in adults. Thyroid lesions are frequently encountered, with a reported prevalence ranging from 4 to 7% in the general population. These lesions often necessitate careful clinical evaluation and, in selected cases, surgical intervention¹.

As previously reported¹-³, subtotal thyroidectomy (ST) was widely performed in thyroid surgery until the late 20th century. However, with advancements in surgical techniques and the introduction of nerve monitoring devices, total thyroidectomy (TT) has become the preferred approach. Although this shift has reduced the recurrence rates of thyroid disease, the risks associated with bilateral dissection, such as hypoparathyroidism and vocal cord paralysis, have increased^2,3.

Due to these risks, thyroid surgery has progressively evolved towards less invasive techniques. According to the 2015 American Thyroid Association (ATA) guidelines, lobectomy with isthmectomy (LI) is recommended as an alternative to TT for patients diagnosed with well-differentiated thyroid cancer with tumor sizes ranging between 1 and 4 cm, provided there is no extrathyroidal extension⁴.

Completion thyroidectomy (CT) is a surgical procedure performed in patients who have previously undergone thyroid surgery due to thyroid cancer or benign goiter. It is indicated in cases where residual thyroid tissue is present, recurrence develops, suspicious nodules are detected, or histopathological examination after LI reveals moderate or high-risk differentiated thyroid cancer. In patients diagnosed with thyroid cancer after LI, CT enhances the effectiveness of radioactive iodine (RAI) therapy and facilitates more reliable monitoring of serum thyroglobulin levels, thereby improving patient follow-up⁵.

Although ST has now been largely abandoned, it was widely practiced in the past, with reported recurrence rates as high as 43%⁶. Consequently, recurrent disease in patients who previously underwent ST remains one of the major indications for CT today. The risk of complications associated with CT is higher than that of primary thyroidectomy, primarily due to the presence of scar tissue from previous surgery; however, this risk varies depending on the initial surgical technique^7,8,9,10.

In recent years, technological advancements have played a significant role in overcoming these surgical challenges. In particular, neuromonitoring systems have contributed to reducing recurrent laryngeal nerve (RLN) injury; gamma probe-assisted radioguided surgery has enabled more precise localization of residual tissue; and energy-based dissection devices (e.g., LigaSure, Harmonic) have facilitated a more controlled and bloodless surgical field^11,12,13.

Despite technological advancements and increased surgical expertise leading to lower complication rates, many surgeons remain hesitant about performing CT due to the challenges associated with a second surgical intervention¹⁴. While concerns over surgical complications may lead some to consider radioactive iodine (RAI) as an initial treatment for residual thyroid tissue, this approach is not widely supported. RAI has limited efficacy in cases without prior complete resection and is less effective at eliminating remnant tissue. Current guidelines emphasize that RAI should follow total thyroidectomy, not replace it^15,16.

Moreover, the necessity of CT remains a subject of debate due to concerns regarding additional surgical stress, time, and financial burden. Therefore, a comprehensive evaluation of complication risks, cost-effectiveness, and clinical benefits is essential when considering the necessity of CT.

This retrospective cohort study analyzed postoperative complications in patients undergoing completion thyroidectomy, classified into two groups based on their initial surgical procedure: LI and ST. Our study aims to evaluate the complication rates and therapeutic efficacy of completion thyroidectomy, determining its safety and necessity in different patient groups. Additionally, the findings are expected to contribute to clinical decision-making processes for surgeons.

Materials and methods

This study was conducted in accordance with the Declaration of Helsinki and was approved by the Non-Interventional Ethics Committee of Hitit University (Decision No: 2024-08). It was designed as a retrospective analysis of patients aged 18 years and older who underwent completion thyroidectomy (CT) at the General Surgery Clinic of Hitit University Erol Olçok Training and Research Hospital between January 2015 and July 2023.

Study criteria

Patients who underwent completion thyroidectomy at the clinic were included in the study, provided they were 18 years or older. Those who had previously undergone neck surgery for non-thyroidal pathologies, had undergone lateral neck dissection, or had a preoperative history of hypoparathyroidism or vocal cord paralysis were excluded. All patients routinely underwent preoperative and postoperative laryngoscopic examination to assess vocal cord function.

Data collection process

Patient data were obtained from hospital records, and variables such as demographic data (age, sex), initial pathology, first and second surgical interventions, second pathology, and postoperative complications were analyzed. Nodule size was measured using ultrasound prior to the completion thyroidectomy (CT) and the largest diameter was recorded for analysis. Fine-needle aspiration biopsy (FNAB) results were classified according to the Bethesda system. Bethesda category data were available for the majority of patients; however, FNAB records could not be retrieved for seven cases due to incomplete archival documentation, and thus their Bethesda classification could not be determined.

Surgical procedures

All surgeries were performed by eight experienced general surgeons, each with at least ten years of experience. All patients included in the study underwent CT and were classified into two groups according to their initial surgical procedures. LI (Group 1) and ST (Group 2). In the LI group, residual thyroid tissue was removed unilaterally. Conversely, cases in the ST group underwent bilateral removal of residual thyroid tissue. Notably, the ST group primarily comprises patients who had previously undergone ST as a precaution against the potential risks associated with TT. ST has historically been performed predominantly in patients with bilateral benign multinodular goiter. In contrast LI is currently favored in the management of unilateral thyroid lesions, whether benign or malignant. Currently, ST is not performed in our clinical practice.

CT indications were established through a combination of FNAB results, Bethesda classification scores, presence of compressive symptoms, and ultrasonographic findings. The detected nodule sizes ranged from 0 to 60 mm. Notably, smaller nodules were often associated with higher Bethesda categories, indicating increased cytological suspicion. In cases where no nodules were observed, completion thyroidectomy was indicated due to the presence of aggressive histopathological features of thyroid cancer following initial LI. In this study, intermittent intraoperative neuromonitoring (IONM) was performed in all cases to assess the functional integrity of the recurrent laryngeal nerve (RLN) during CT. In the majority of cases, surgical dissection was performed using a harmonic scalpel, which offers the advantage of simultaneous cutting and coagulation, thereby reducing intraoperative bleeding and operative time.

Complications

Postoperative complications were classified as transient or permanent hypoparathyroidism, unilateral or bilateral recurrent laryngeal nerve (RLN) injury (transient or permanent), hematoma requiring reoperation, and tracheostomy due to nerve injury. Hypoparathyroidism was diagnosed based on calcium, phosphorus, albumin, and parathyroid hormone (PTH) levels. Patients whose PTH levels returned to normal within one year, who did not require medication, and who showed no signs of hypocalcemia were classified as having transient hypoparathyroidism, whereas those who required continued treatment beyond one year were classified as having permanent hypoparathyroidism. RLN injuries were assessed through indirect laryngoscopy and vocal cord examination, and cases where vocal cord paralysis persisted for more than one year were considered permanent RLN injuries. Cases requiring tracheostomy due to nerve damage were also documented. Hematomas requiring reoperation were identified through clinical examination and physical assessment.

Statistical analysis

The data obtained in this study were analyzed using SPSS (Statistical Package for the Social Sciences) version 27.0. The Shapiro-Wilk test was used to assess the normality of data distribution. Continuous variables were compared using either parametric tests (t-test) or non-parametric tests (Mann-Whitney U test), depending on the distribution of the data. For the comparison of categorical variables, the chi-square (χ²) test was applied.

All data were presented as percentages (%) and frequency distributions, and the results of significance tests were reported using p-values. A p-value of less than 0.05 (p < 0.05) was considered statistically significant for differences between groups.

To evaluate the relationship between potential risk factors and postoperative complications, both univariate and multivariate logistic regression analyses were performed. In the univariate analysis, each variable was assessed individually. Variables that were clinically relevant or statistically significant (p < 0.10) were included in the multivariate model. The following variables were considered in the multivariate logistic regression: age, gender, duration of surgery, nodule size, and type of previous thyroidectomy (lobectomy or subtotal thyroidectomy). Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to estimate the strength of associations. A p-value of less than 0.05 was considered statistically significant. All analyses were conducted using SPSS version 27.0 (IBM Corp., Armonk, NY).

Results

Among the 70 patients included in our study, 11 (15.7%) were male and 59 (84.3%) were female. The mean age was calculated as 51.11 years. Among the 70 patients, 18 (25.7%) had previously undergone LI (Group 1), while 52 (74.3%) had undergone ST (Group 2). The demographic comparison between patients undergoing lobectomy (n = 18) and subtotal thyroidectomy (n = 52) revealed no statistically significant differences across key variables. Age distribution showed that the majority in both groups were aged ≥ 45 years (p = 0.527). Female patients predominated in both groups, with a similar gender ratio (p = 0.716). The time interval between the first and second surgeries was comparable, although a slightly higher proportion of lobectomy patients underwent reoperation within 10 years (38% vs. 18%, p = 0.242) (Table 1).

Table 1.

Baseline demographic and initial histopathological features in patients undergoing completion thyroidectomy after prior lobectomy or subtotal thyroidectomy.

	LI(N = 18)	ST (N = 52)	P value
Age			0.527
< 45	7 (38.9%)	16 (30.8%)
≥ 45	11 (61.1%)	36 (69.2%)
Sex			0.716
Male	2 (11.1%)	9 (17.3%)
Female	16 (88.9%)	43 (82.7%)
Interval between surgeries (years)			0.242
0–10	7 (38.9%)	10 (19.2%)
11–20	7 (38.9%)	28 (53.8%)
21–30	4 (22.2%)	14 (26.9%)
Histopathology results of initial surgery			0.275
Benign	9 (50.0%)	33 (63.5%)
Papillary carcinoma	5 (27.8%)	5 (9.6%)
Medullary carcinoma	0 (0.0%)	1 (1.9%)
Not available	4 (22.2%)	13 (25.0%)

Regarding initial histopathological findings, benign pathology was the most common in both cohorts. Papillary carcinoma was identified in 5 patients in each group, while medullary carcinoma was rare (only 1 case in the subtotal thyroidectomy group). The percentage of cases with unknown initial pathology was slightly higher in the subtotal thyroidectomy group (25%) than in the lobectomy group (22%) (p = 0.275) (Table 1).

When comparing nodule size between the LI and ST groups, a statistically significant difference was observed (p = 0.049). In the LI group, smaller nodules (≤ 10 mm) were more prevalent, accounting for 33.3% of cases, compared to only 9.6% in the ST group. In contrast, nodules measuring 11–40 mm were more frequently encountered in the ST group (71.2%) than in the LI group (55.6%). There was no statistically significant difference in FNAB Bethesda classification between LI and ST groups. In the comparison between LI and ST groups, postoperative histopathology did not reveal a statistically significant difference (p = 0.544). Malignancy was detected in 3 out of 18 patients (16%) in Group 1, and all cases were classified as papillary thyroid carcinoma. In Group 2, malignancy was identified in 10 out of 52 patients (19%), including 7 cases (13.4%) of papillary thyroid carcinoma, 1 case of follicular carcinoma, 1 case of medullary carcinoma, and 1 case of undifferentiated thyroid carcinoma. In one case categorized histopathologically as ‘normal thyroid tissue’ following initial lobectomy, further microscopic examination revealed a large encapsulated follicular variant tumor with capsular invasion. Although no lesion was detected in the remaining contralateral lobe, CT was performed to facilitate RAI therapy and reduce the risk of recurrence (Table 2).

Table 2.

Preoperative nodule size, cytological classification, and postoperative histopathological outcomes according to prior surgical type.

Nodule size (mm)	LI(N = 18)	ST(N = 52)	P value
			0.049
0–10	6 (33.3%)	5 (9.6%)
11–20	1 (5.6%)	13 (25.0%)
21–40	9 (50.0%)	24 (46.2%)
> 40	2 (11.1%)	10 (19.2%)
FNAB Bethesda classification			0,579
I. Nondiagnostic	4 (22.2%)	13 (25.0%)
II. Benign	5 (27.8%)	19 (36.5%)
III. Atypia of undetermined significance	4 (22.2%)	5 (9.6%)
IV. Follicular neoplasm/suspicion	1 (5.6%)	2 (3.8%)
V. Suspicious for malignancy	1 (5.6%)	5 (9.6%)
VI. Malignant	0 (0%)	4 (100%)
Postoperative histopathology			0.544
Benign	14 (77.8%)	42 (80.8%)
Papillary carcinoma	3 (16.7%)	7 (13.5%)
Medullary carcinoma	0 (0.0%)	1 (1.9%)
Follicular carcinoma	0 (0.0%)	1 (1.9%)
Anaplastic/undifferentiated	0 (0.0%)	1 (1.9%)
Normal thyroid tissue	1 (5.6%)	0 (0.0%)

A total of 21 patients (30%) experienced various complications. In the comparison of complications, the incidence of transient hypoparathyroidism was 5.5% (1/18) in Group 1, whereas in Group 2, transient hypoparathyroidism was observed in 13.4% (7/52), and permanent hypoparathyroidism was found in 5.7% (3/52). RLN injury was observed in only one patient (5.5%) in Group 1, presenting as unilateral transient paralysis. However, in Group 2, RLN injury was detected in 9 patients (17.3%), with 7 cases involving unilateral paralysis. Tracheostomy was performed on two patients who developed bilateral paralysis, However, long-term follow-up confirmed that these two cases were transient injuries. Group 2, two patients required reoperation due to hematoma. When hypoparathyroidism and RLN injury were evaluated separately, no statistically significant difference was found between the groups. However, when the overall complication rates were compared, a significant difference was observed between Group 1 (11%) and Group 2 (36.5%) (p = 0.04) (Table 3).

Table 3.

Postoperative complications in patients undergoing completion thyroidectomy after prior lobectomy or subtotal thyroidectomy.

	LI(N=18)	ST(N=52)	P value
Hypoparathyroidism			0.356
Temporary	1 (5.6%)	7 (13.5%)
Permanent	0 (0.0%)	3 (5.8%)
Vocal cord paralysis			0.441
Unilateral	1(% 5,5)	7(%13,4)
Bilateral	0 (0.0%)	2(%3,8)
Temporary	1(% 5,5)	6(%11,5)
Permanent	0 (0.0%)	3(%5,7)
Hematoma	0 (0.0%)	2(%3,8)	1.000-fischer
Hoarseness	1(%5,5)	8(%15,3)	0.430-fisher
Tracheostomy	0 (0.0%)	2(%3,8)	1.000- fischer
Complication	2(%11,1)	19(%36,5)	0.042

Pearson’s Chi-Square test was used for group comparisons. As 25% of expected cell counts were below 5, Fisher’s Exact Test was applied

When analyzing the relationship between nodule size and complication rates, nodule size was found to be significantly larger in Group 2 compared to Group 1 (p = 0.049). Among patients who developed complications, the mean nodule diameter was 35.2 mm, whereas in those without complications, it was 23.9 mm (p = 0.03) (Fig. 1).

Fig. 1.

Comparison of nodule size between patients with and without complications. The box plot illustrates the distribution of nodule size (mm) in patients with (Present) and without (Absent) postoperative complications. The mean nodule size is higher in the complication group, indicating a significant association between larger nodules and increased complication rates (p = 0.03).

In patients who developed complications, the time between the first and second surgeries was significantly longer 20 (15.5–25.0 years) compared to those without complications 15 (8–20 years) (p = 0.006).

When analyzing the relationship between nodule size and complication rates, nodule size was found to be significantly larger in Group 2 compared to Group 1 (p = 0.049). Among patients who developed complications, the mean nodule diameter was 35.2 mm, whereas in those without complications, it was 23.9 mm (p = 0.03) (Fig. 1).

In patients who developed complications, the interval until the second surgery (20.2 ± 7.2 years) was significantly longer compared to those without complications (14.0 ± 8.6 years) (p = 0.005). Furthermore, when comparing both groups in terms of nodule size, a statistically significant difference was observed in the group with complications (p = 0.002) (Table 4).

Table 4.

Comparison of various risk factors with complication development in patients undergoing completion Thyroidectomy.

Variable	No complicationn = 49	Complicationn = 21	p-value
Age (years), mean (SD)	49.8 (11.7)	54.1 (16.1)	0.211
Gender, n (%)			1.000
Male	8 (16.3%)	3 (14.3%)
Female	41 (83.7%)	21 (85.7%)
Interval between surgeries (years), mean (SD)	14.0 (8.6)	20.2 (7.2)	0.005
Nodule size (mm), mean (SD)	23.9 (13.5)	35.2 (13.8)	0.002
Type of surgery, n (%)			0.042
Lobectomy with isthmectomy	16 (88.9%)	2 (11.1%)
Subtotal thyroidectomy	33 (63.5%)	19 (36.5%)

According to the univariate logistic regression analysis, postoperative complications in patients who underwent completion thyroidectomy were considered as the dependent variable (no complication vs. complication), while gender, age, and type of surgery were considered as independent variables. Nodule size and the interval between the two operations were treated as confounding factors. As a result, nodule size (p < 0.005) and the time interval between the two surgeries (p < 0.009) were identified as significant influencing factors that increased the likelihood of developing complications (Table 5).

Table 5.

Factors associated with the development of complications in patients undergoing completion thyroidectomy: logistic regression analysis.

Variable	Univariate	95% CI	p-value	Multivariate*	95% CI	p-value
	OR			OR
Gender
Female (Ref)	–	–	–	–	–	–
Male	0.85	0.23–3.60	0.830	–	–	–
Age (years)	1.02	0.98–1.07	0.212	–	–	–
Interval between surgeries (years)	1.11	1.07–1.19	0.009	1.08	0.98–1.17	0.109
Nodule size (mm)	1.06	1.02–1.11	0.005	1.04	0.99–1.09	0.078
Previous surgery	–	–	–	3.69	0.69–19.75	0.128
Type of initial surgery
Lobectomy with isthmectomy (Ref)	–	–	–	–	–	–
Subtotal thyroidectomy	1.93	0.95–22.24	0.057	–	–	–

OR Odds ratio, CI Confidence interval, Ref Reference category *Only variables with clinical or statistical relevance in univariate analysis were included in multivariate analysis.

A multivariate logistic regression analysis was performed in which the identified predictors and histopathological features were treated as dependent variables, and the independent variables were those included in the model. The Hosmer–Lemeshow goodness-of-fit test (χ² = 6.841, df = 8, p = 0.554) indicated a good fit of the model. The analysis showed that patient age, nodule size, type of previous surgery, and the interval between the two operations were not independent predictors of complication development (Table 5).

Discussion

Secondary surgical interventions for thyroid diseases present significant challenges due to factors such as inflammation, edema, and postoperative adhesions, making these procedures high-risk. These risks have driven a shift in thyroid surgery from ST to TT over time. Particularly in cases requiring a second surgical intervention, bilateral dissection is expected to increase the risk of complications. However, in CT, where only unilateral dissection is performed, complication rates remain a subject of debate^17,18. However, recent studies emphasize that primary TT can be performed safely in well differentiated thyroid cancers, with low early complication rates¹⁹.

A multicenter study comparing 245 CT patients who had previously undergone lobectomy with primary total thyroidectomy found that complication rates in the CT group were significantly lower than those in the primary TT group²⁰. In our study, the rates of transient hypoparathyroidism and unilateral RLN injury in the lobectomy group were both 5.5%, whereas in the study by Canu et al., the rate of unilateral RLN injury was 2.86%, and no cases of hypoparathyroidism were reported. This discrepancy may be attributed to differences in sample size. Another study evaluating completion thyroidectomy performed for recurrent benign nodular goiter reported no cases of hypoparathyroidism or nerve injury among 30 patients who underwent contralateral lobectomy²¹. However, in the study by Rudolph et al., which included 259 CT patients with recurrent benign goiter, the total RLN injury rate was 6.9%, and the hypoparathyroidism rate was 15%. However, permanent nerve injury occurred in only 0.77%, and permanent hypoparathyroidism was observed in 1.54% ²².

In another study published in 2019, which included 100 CT cases with contralateral lobectomy, no cases of RLN injury, hypoparathyroidism, or hematoma were reported, emphasizing that CT may be a safe and preferable option in the absence of financial and patient-related concerns²³. In our study, among CT cases involving unilateral exploration (Group 1), transient hypoparathyroidism and unilateral transient RLN injury each occurred in 5.5% of patients, and no permanent complications were observed. The complication rates in Group 1 were consistent with those reported in similar studies in the literature, reinforcing the notion that contralateral lobectomy in CT can be performed safely with low complication rates.

ST was historically considered the gold standard for the surgical treatment of benign multinodular goiter until the late 20th century, as it was associated with a lower complication risk and did not necessitate lifelong hormone replacement therapy^24,25. However, the high recurrence rate in ST patients has increased the need for reoperations, leading to a higher complication risk². In our study, the majority of CT cases belonged to Group 2, comprising patients who had previously undergone bilateral ST. Indications for CT included enlarging or symptomatic nodules, compressive symptoms, suspicious or malignant cytology (Bethesda categories 3–6), postoperative diagnosis of malignancy, and disease recurrence. Although unilateral reoperation may be technically sufficient in many cases, the bilateral nature of prior ST often results in residual tissue on both sides. Therefore, while unilateral surgery may be adequate in selected patients, bilateral CT was warranted in others to ensure treatment efficacy or to facilitate postoperative radioactive iodine (RAI) planning. The indications for reoperation in these cases were determined based on compressive symptoms or fine-needle aspiration biopsy (FNAB) results classified as Bethesda 3–6. Due to adhesion and fibrosis resulting from prior surgery, higher complication rates were expected in these cases.

In our study, among patients who had previously undergone ST, the rates of transient and permanent hypoparathyroidism were 13.4% and 5.7%, respectively. In this group, permanent RLN injury occurred in 5.7% of cases, whereas transient RLN injury was observed in 11.5%. Furthermore, tracheostomy was required in 3.8% of cases due to early postoperative bilateral paralysis. Additionally, emergency reoperation was necessary in 3.8% of Group 2 patients due to hematoma related respiratory distress. When complication rates were compared between Group 1 (LI) and Group 2 (ST), the overall complication rate was significantly higher in Group 2 (p = 0.04).

A similar study conducted by Kurman et al., which included 109 CT cases, found that no complications occurred in patients whose first surgery was lobectomy, whereas in the ST group, RLN injury was reported in 3.8%, and hypoparathyroidism was observed in 1.3%, with significant differences in nerve injuries between the groups²¹. Similarly, in the study by Rudolph et al., the ST group had a permanent RLN injury rate of 3.4% and a permanent hypoparathyroidism rate of 5.1%, with significantly higher complication rates compared to the TT group²². The findings of our study are consistent with these reports in the literature, suggesting that CT is associated with a higher risk of complications, particularly in cases requiring bilateral dissection. Notably, studies that have reported low complication rates for CT often include a predominance of lobectomy cases, which may contribute to the observed differences^26,27. These findings indicate that the primary surgical procedure and technique significantly impact CT outcomes.

In patients whose first surgery was ST, postoperative complication rates following CT were observed to be higher than those following primary total thyroidectomy^14,23. Based on these findings, it may be beneficial that ST has largely been abandoned over time. Instead, performing lobectomy for unilateral lesions and TT for bilateral lesions may protect both patients and surgeons from reoperation-associated complications. Although complication rates in our study were relatively high, the detection of malignancy in 19.2% of cases undergoing postoperative histopathological examination after ST highlights the oncological significance of CT. This finding underscores the importance of reassessing residual thyroid tissue for malignancy following ST and suggests that, despite its high complication risk, CT may serve as an effective oncological surgical approach.

Although near-infrared autofluorescence devices have shown promise in parathyroid gland identification, such technology was not employed in our series. Parathyroid glands were identified using conventional visual inspection. While helpful for reducing postoperative hypoparathyroidism, this method is not yet routinely used in our institution and should be considered when evaluating our complication rates²⁸.

Devices like harmonic scalpel (HS) and LigaSure (LS) are widely used in thyroid surgery. A recent study shows both have similar safety profiles regarding bleeding requiring reoperation, though HS may offer better hemostasis in carcinoma cases²⁹. In our study, HS was utilized in the majority of cases. In the ST group, two patients required reoperation due to postoperative hematoma. However, the specific instrumentation used in each individual case was not systematically documented, thereby limiting the scope of our analysis regarding device-related outcomes.

Technological advancements in surgery have accelerated in recent years, with the integration of Internet of Things (IoT) systems marking a major innovation. In thyroid surgery, IoT-supported nerve monitoring enables real-time alerts and data flow, helping surgeons prevent recurrent laryngeal nerve injury and improve outcomes³⁰. Currently, due to concerns regarding surgical complications, there is a growing preference for less invasive techniques in the management of thyroid nodules. For recurrent benign or malignant cases, thermal ablation methods such as laser ablation have emerged as viable alternatives to surgery. While nodules smaller than 1 cm particularly papillary thyroid microcarcinomas are often considered suitable for ablation, benign nodules treated with this approach are typically larger, frequently ranging from 3 to 5 cm or beyond, depending on institutional experience and technical feasibility³¹.

The Bethesda classification system is widely used for cytological evaluation of thyroid nodules. In our cohort, malignancy rates were 4.2% for Bethesda category II and 22.2% for category III, these findings further support the clinical utility of the Bethesda system^32,33.

In thyroid surgery, the surgeon’s level of experience is another factor that may influence patient outcomes. Previous studies have consistently demonstrated that surgical experience significantly influences postoperative outcomes in thyroidectomy, particularly in minimizing complications such as recurrent laryngeal nerve injury and hypoparathyroidism. Therefore, our study included cases operated on by surgeons with at least ten years of clinical experience³⁴.

Recurrent laryngeal nerve (RLN) injury may impair postoperative voice quality and overall quality of life, particularly through persistent hoarseness and aspiration. Prior studies have shown that even transient RLN dysfunction can lead to prolonged recovery and functional limitations. Another complication Persistent hypoparathyroidism may significantly impair quality of life due to chronic symptoms such as muscle cramps, paresthesia, and fatigue, often requiring ongoing calcium and vitamin D supplementation. In our study, routine use of intraoperative neuromonitoring and surgeon experience likely contributed to preserving nerve function and reducing patient discomfort^35–37.

Our study also examined the association between nodule size and complications, revealing that larger nodules were more frequently associated with complications. A study by Ma et al. reported that patients with larger nodules had higher complication rates and that earlier surgical intervention could reduce complications. However, this study focused on primary thyroid surgery, and the literature on the relationship between nodule size and surgical complications in CT cases remains limited³⁸. To establish more conclusive evidence, further randomized controlled trials are required.

Limitations

The retrospective nature of the study, the fact that surgeries were performed by different surgeons, and the limited sample size are among the primary limitations of our study. Additionally, absence of a primary TT control group limits the ability to compare CT outcomes directly with those of initial TT. The primary objective, however, was to compare CT outcomes based on the type of previous surgery (ST vs. LI), which represents a common clinical decision point for surgeons.

The sample size was relatively small, with only 70 patients included from a single center. Particularly, the TL group had a limited number of patients (n = 18), which may reduce the statistical power of comparisons between groups. This imbalance reflects historical surgical preferences in the region, where ST was more frequently performed.

Finally, the study focused solely on structural complications such as hypoparathyroidism and recurrent laryngeal nerve injury. Functional outcomes including voice quality, dysphagia, or return to normal daily activity were not evaluated due to the retrospective design and limited availability of such data in patient records. These functional metrics could provide important insights into patient-centered outcomes and should be included in future prospective studies.

Conclusion

Our findings emphasize the importance of thorough surgical planning in patients with a history of bilateral subtotal thyroidectomy, due to an elevated risk of postoperative complications such as hematoma and reoperation. Completion thyroidectomy following initial lobectomy was associated with acceptable safety outcomes. In this context, careful preoperative assessment to identify cases with high operative risk such as those with extensive fibrosis or prior complex surgery remains essential. The integration of advanced intraoperative technologies, combined with the expertise of experienced surgeons, is expected to enhance surgical outcomes. In light of the declining use of subtotal thyroidectomy and evolving operative techniques, completion thyroidectomy may be performed with reduced complication rates in future clinical practice. Further well-designed prospective studies are warranted to validate this prediction.

Author contributions

OA: Writing – review & editing, Supervision, Methodology, Conceptualization MŞ: Data curation Formal analysis Software Writing–original draft. RT: Funding acquisition Investigation Project administration AKP: Investigation Resources Validation. İS: Investigation Project administration Software Visualization MAY: Investigation Resources Validation ER: Investigation Project administration Software Visualization All authors approved the final version of the manuscript to be published.

Data availability

The data that support the findings of this study are not openly available due to reasons of sensitivity and privacy are available from the corresponding author upon reasonable request. Data are located in controlled access data storage at Hitit University Faculty of Medicine Department of General Surgery.

Declarations

Competing interests

The authors declare no competing interests.

Ethics approval and consent to participate

This exploratory, retrospective, single-center cohort study was conducted in accordance with the most recent version of the Declaration of Helsinki. This study was conducted in accordance with the Declaration of Helsinki and was approved by the Non-Interventional Ethics Committee of Hitit University (Decision No: 2024-08). Given the retrospective design of the study, the ethics committee granted a waiver for written informed consent. The informed consent was waived by IRB (Clinical Research Ethics Committee of Hitit University Faculty of Medicine) The data collection and manuscript preparation processes were conducted in accordance with the guidelines set forth by the Committee on Publication Ethics (COPE) and the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) initiative.