Transoral Endoscopic Thyroidectomy: Review of 81 Cases in a Single Institute

Introduction

Along with the development of minimally invasive techniques as well as the increasingly higher requirements of patients on cosmetic surgery, the approach for endoscopic thyroidectomy has experienced multiple developmental processes, including axillary approach, breast approach, axillo-bilateral-breast approach and so on.^1–4 The aim of these surgical approaches is to minimize and hide the incision. However, those approaches leave scars on the skin surface without exception; moreover, the incision is far away from nodule, which leads to greater surgical tunnel trauma than traditional open surgery, so it has been actually divorced from the concept of minimal invasion for the sake of cosmetology.

Natural orifice transluminal endoscopic surgery (NOTES) possesses the superiorities of minimal invasion, scar-free on body surface, and aesthetics. ⁵ Therefore, it is increasingly widely applied in many surgical diseases.^6–8 Transoral endoscopic thyroidectomy (TOET) satisfies the characteristics of NOTES. Doctor Wilhelm from Germany successfully performed the first case of TOET in 2009. ⁹ Recently, a few studies have preliminarily reported the safety and feasibility of TOET.^10,11 However, this surgical procedure has just begun to be applied in clinic with few treatment cases and short follow-up period, so more clinical studies are required so as to provide more evidence to support this kind of surgery approach.

Our hospital is one of the earliest hospitals to perform TOET. Therefore, we review our experiences and evaluate the safety and efficacy of TOET in patients with thyroid nodules.

Materials and Methods

Inclusion criteria were as follows: benign tumor diameter <5.0 cm evaluated by B ultrasound; malignant tumor without cervical lymph nodes metastasis; and patients with cosmetic requirements. Exclusion criteria were as follows: maximum tumor diameter >5.0 cm; cancer cases with metastasis in cervical lymph nodes; Graves' disease; patients with a history of surgery or radiation of the neck; and severe coagulation disorders. A total of 81 patients who met the study criteria were informed about the risks and benefits and performed TOET in General Surgery Department of Zhongshan Hospital of Xiamen University from November 2011 to September 2015. The study was approved by the Ethics Committee of the Hospital, and all operations were performed by the same experienced laparoscopic surgeon.

Seventy-nine out of the 81 patients were female, and 2 cases were male, with the average age of 34.2 ± 9.4 years. All cases were diagnosed with benign nodules such as thyroid neoplasm, nodular goiter, and nodular goiter accompanying with cystic degeneration. Preoperative ultrasound revealed unilateral nodules in 65 cases, with the average diameter of 3.35 ± 0.99 cm; bilateral nodules in 5 cases, with the average diameter of 3.44 ± 0.63 cm; and isthmus nodules in 6 cases, with the average diameter of 2.35 ± 0.81 cm. Of these, 5 cases were diagnosed unilateral papillary thyroid cancer by intraoperative pathology, with the average diameter of 3.76 ± 1.81 cm (Table 1).

All cases received preoperative conventional thyroid function test, thyroid B ultrasound, and thyroid emission computed tomography. Meanwhile, intraoperative pathological examination was carried out so as to determine nodules property. All patients received preoperative chlorhexidine mouthwash, and prophylactic antibiotics were given before anesthesia.

Operative techniques

The transnasal endotracheal intubation was adopted for general anesthesia. Patients were given intravenous infusion of cefathiamidine preoperatively (an additional dose was given if the surgery lasted for over 3 hours). Patients were in supine position with head hypsokinesis, and their necks were straightened with cushioning being placed under the shoulder, so that the necks were in slight hyperextension position. Operator and assistants stood in the head side of patients, while the monitor was placed on the right side of patients. Transoral approach was adopted; about 10 mL of diluted adrenaline solution (1:200,000) supplemented with 1% lidocaine was subcutaneously injected into the oral floor mucosa and the openings of sublingual ducts in front of the tongue frenulum to extend adsorption time of local anesthetics and reduce intraoperative hemorrhage as well as postoperative pain.

The first 10 mm incision was made at the center of oral floor mucosa, which located in front of tongue frenulum. Subsequently, anterior cervical area could be reached passing through mylohyoid, geniohyoid and anterior digastric muscle by a blunt dissection with scissors. After part of operation space was constructed, a 5 mm trocar was placed and CO₂ was insufflated with the pressure maintaining at about 4–8 mmHg (Fig. 1A). The 5 mm special laparoscope equipped with scissors in the front (STORZ, the first two surgeries were provided by Professor Thomas Wilhelm) was placed, followed by a blunt dissection of the deep loose connective tissue of platysma to expand working space. For the rest of the operations, we did not use this particular laparoscopy anymore and Mesnager scissors were adopted to create a working space from the mandibular area to the anterior neck, and then the 5 mm Trocar was placed. Next, two 0.5 incisions were made at the lateral sides of the bilateral canine teeth, and attention should be paid to avoid the mental nerve. Two 5 mm trocars were placed separately after blunt dissection by scissors, and the trocars were wrapped with saline gauze to fix trocar to protect teeth (Fig. 1B). Subsequently, the surgical instrument and ultrasonic scalpel were inserted to isolate the loose connective tissues under direct vision to create working space, with the inferior border reaching suprasternal fossa and the lateral borders reaching the anterior edge of sternocleidomastoid muscle. The linea alba cervicalis was then opened and blunt dissection of bilateral jugular anterior fascicles was conducted until the thyroid tissue was exposed.

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FIG. 1.

Creation of the trocars. (A) One 10 mm midline incision and insertion of the 5 mm trocar, (B) two 5 mm lateral incisions and two 5 mm trocars.

The thyroidectomy was performed according to the respective condition of patients. For a unilateral benign nodule, unilateral subtotal resection was used. For bilateral benign nodules, subtotal resection was performed. Total thyroidectomy with central node dissection was carried out for papillary thyroid cancer. For unilateral subtotal thyroidectomy procedure, the thyroid tissues containing nodules were removed from upper pole of thyroid to bottom. First, thyroid isthmus was dissected and transected by ultrasonic scalpel; attention should be paid not to put the functional surface of ultrasound scalpel upward, so as to prevent tracheal injury. Subsequently, thyroid was dissociated from the lateral side; middle thyroid vein was isolated and ligated; and the dissociated inferior thyroid vein and artery were exposed downward, solidified, and cut off with ultrasound scalpel, which should be as far away from recurrent laryngeal nerve region as possible. The upper and inferior vessels should be transected close to the thyroid tissue, so as not to injure the superior laryngeal nerve and recurrent laryngeal nerve. The removed specimens were taken out along with the trocar from the middle incision. Large tumor could be dissected in a specimen bag and taken out separately under direct vision if it could hardly be taken out as a result of large size. Surgical field was washed, followed by hemostasis, with or without drainage after surgery. Incisions were interruptedly sutured with 4-0 Vicryl. Antibiotics were applied once after surgery, liquid diet was allowed 6 hours after surgery, and tinidazole mouthwash was given to rinse mouth after each meal.

Contents of follow-up mainly focused on the possible recurrence and long-term complications of TOET, including neck paresthesia, limitation of neck movement, and possible changes in speech, chewing, swallowing, oral sensory function, and limitation in opening mouth after surgery. All patients were followed up for over 15 months, with once in 1st, 3rd, and 6th month after surgery, respectively, and once every 6 months afterward. The patients' cosmetic satisfaction was recorded.

Results

Seventy-nine patients in this group were performed TOET successfully, and 2 (2.5%) cases were conversed from endoscopic to open thyroidectomy due to air embolism and rescued successfully. Total thyroidectomy with central compartment dissection was performed for 5 (6.2%) patients; subtotal bilateral thyroidectomy was performed for 5 (6.2%) patients; and isthmus thyroidectomy and subtotal unilateral thyroidectomy was carried out for 6 (7.4%) and 65 (80.2%) patients, respectively (Table 2).

The average duration of operation was 89.0 ± 38.6 minutes, and the intraoperative amount of bleeding was 29.3 ± 27.6 mL. The duration of subtotal unilateral thyroidectomy was 90.1 ± 39.8 minutes, and the intraoperative amount of bleeding was about 26.3 ± 20.6 mL; the duration of isthmus thyroidectomy was 60.3 ± 8.2 minutes, and the intraoperative amount of bleeding was about 15.2 ± 7.8 mL; the duration of subtotal bilateral thyroidectomy was 100.0 ± 35.4 minutes, and the intraoperative amount of bleeding was about 28.6 ± 16.4 mL; the duration of papillary thyroid carcinoma was 115.0 ± 14.1 minutes, and the intraoperative amount of bleeding was about 55.0 ± 31.6 mL (Table 2).

Two (2.5%) cases experienced air embolism. They have a suddenly dropped blood pressure, increased heart rate, and decreased oxygen saturation in the time of infusing CO₂ for constructing surgical space. Precardial Doppler reveals gas formation, and air embolism was diagnosed. Endoscopic operation was ceased immediately; patients were in left lateral decubitus with elevated right shoulder, and external chest compressions as well as high flow oxygen inhalation were carried out. Vital signs return to normal after intravenous injection of dexamethasone, aminophylline, and dopamine. Both patients had recovered well and discharged.

Perioral numbness occurred in 2.5% of the patients on day 1 after surgery, the sensory function of whom returned to normal level after symptomatic treatment. Opening mouth pain occurred in 2 (2.5%) of the patients and increased swallowing saliva occurred in 2 (2.5%) of the patients. Two (2.5%) patients existed neck discomfort, and 4 (4.9%) patients developed infection. For the first 49 patients in this group, no drainage tube was placed, and 2 (4.1%) cases had inflammatory mass in anterior cervical regions. The latter 32 cases were placed negative pressure drainage tube after surgery to reduce infection rate, while inflammatory mass in anterior cervical regions could still be observed in 2 (6.2%) cases. After given puncture drainage and anti-infection therapy, all patients recovered well and were discharged without obvious scar in patients with indwelling drainage tube. Complications such as hoarseness, drinking bucking, hemorrhage, hyperspasmia, and parathyroid gland injury were not found in this group (Table 3). The average postoperative length of stay was 4.77 ± 2.61 days, and oral mucosal incisions were well healed (Fig. 2A–C).

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FIG. 2.

The incisions after surgery. (A) The right-side incision (black arrow) on day 5, (B) the left-side incision on day 5, (C) the middle incision on day 5, (D) follow-up at 1 month.

All patients receiving long-term postoperative follow-up had no paresthesia of mandibular and neck or limitation of neck motion, no obvious abnormalities in speech, chewing, swallowing and oral sensory function, and no recurrence after surgery. All the patients were fully satisfied with the cosmetic outcome of the surgery (Fig. 2D).

Discussion

The existing approaches of endoscopic thyroid surgery have not yet achieved the perfect balance between cosmetic effect and minimal invasion. The axillary or breast approach seems to be more invasive than conventional open surgery because these approaches require more extensive dissection of subcutaneous layers to get enough working space from the trocar sites to the thyroid, thereby increasing the risk of hematomas, numbness in the neck and anterior chest skin, or severe scarring. Compared with surgery of axillary or breast approach, transoral approach has greatly reduced the tunnel distance and tissue injury. Theoretically, TOET well satisfies patients' cosmetic requirements in the meantime of being minimally invasive. Consequently, it is undoubtedly a better choice for patients especially for young female.

To avoid unnecessary surgery, fine needle aspiration (FNA) should be routinely performed to evaluate the property of thyroid nodule preoperatively. In this group, FNA examination has been performed in 70.4% of the patients and shows benign nodules, but they still strongly asked for surgical treatment due to fear of malignant transformation or aesthetic consideration. In some patients, the thyroid nodules were progressively increased during follow-up period, resulting in oppressive symptoms or severe anxious mood, they refused to do FNA and strongly require direct surgical treatment. According to the American Thyroid Association (ATA) guidelines, it is a relative surgical indication that patients who strongly require surgical treatment due to the appearance or severe anxiety and thus affect the normal life. Since most of the patients in this group are young women who have a high demand for beauty, TOET is a better choice for them due to its minimal invasion and excellent aesthetic effect.

However, such a surgical procedure is still in preliminary clinical application stage. Thus, its short-term and long-term complications remain to be further explored and studied. The short-term complications we have reported before include infection, opening mouth pain, increased saliva in swallowing, air embolism, and so on. ¹² However, its long-term complications remain unclear yet. In this study, the main postoperative complication of TOET is local infection, with the incidence rate as high as 7.4%, which is higher than the infection rate (0.1%) of other approach of endoscopic thyroidectomy in our hospital as well as the incidence reported in other literatures (0%–1.6%).^4,13,14

The incidence of transient neck paresthesia is 3.9%, perioral numbness is 2.5%, and opening mouth pain is 2.5%. Increased saliva in swallowing occurred in 2.5% of patients and air embolism occurred in 2.5% of patients. All the above-mentioned complications were transient and recovered well after positive symptomatic treatment. Complications such as hoarseness, hemorrhage, hyperspasmia, and parathyroid gland injury are not found in this group which is relatively lower than previous reports of endoscopic thyroidectomy via other approaches.^4,13,15,16 Furthermore, there was no recurrent case, skin paresthesia, limitation of neck motion, and abnormalities in speech, chewing, swallowing, and oral sensory function observed during our long-term follow-up. These results verified the safety, feasibility, and effectiveness of such surgical procedure.

Wilhelm and Metzig ¹⁷ proposed that indications for TOET were thyroid volume <30–40 mL and solitary thyroid nodule <2 cm. In this group, the greatest long diameter is about 5.0 cm, and the average diameter is >2 cm. According to our experience, great specimen can be dissected and taken out separately. This kind of operation is also suitable for bilateral multiple nodules, but it is demanding on operator's technique and experience. Based on our experience, such surgical procedure is associated with the following major advantages: (1) scar-free on body surface; (2) shorter route, less injury, and rapider recovery; (3) whole body shower is allowed at the early stage; (4) top-down lymph node dissection in the central area along recurrent laryngeal nerve is good for exposing and protecting recurrent laryngeal nerve; and (5) compared with other approaches in endoscopic surgery, the lymph node dissection in neck central area can reach the pleura, which is allowed for a better lymph node dissection. Therefore, the lobe and isthmus resection of thyroid carcinoma as well as lymph node dissection in central area can be carried out after technology maturity. We are now carrying out clinical exploration in this aspect. However, it is also associated with certain drawbacks: (1) converting type I incision to type II incision, which increases chance of infection; (2) change in operation habit, namely, to carry out top-down surgery, which need some time for doctors to adapt it; (3) upper pole of thyroid gland can hardly be exposed, which makes it difficult for total thyroidectomy in patients with higher upper pole; and (4) the operation space is narrow and consequently the instruments can interfere with each other.

TOET surgery changes type I incision in traditional thyroid surgery into type II incision, which has increased probability of postoperative infection as a result of a great amount of oral flora. The first 49 among the 81 cases in our department have no indwelling drainage tube, and 3 cases have inflammatory mass in anterior cervical regions after surgery. The latter 32 cases are placed negative pressure drainage tube after surgery to reduce infection rate. However, inflammatory masses in anterior cervical regions still happened in 3 cases. Consequently, high attention should be paid to preoperative and postoperative oral nursing, so as to reduce pathogenic bacteria entering surgical site from incision. Administration of tinidazole mouthwash moist gauze ball for washing and gargling 1 day before surgery and 0.05% Chlorhexidine mouthwash for oral nursing before surgery are recommended. It is best to use antibiotics based on the phlegm culture and drug sensitivity test. Moreover, 5 mg chymotrypsin and 5 mg dexamethasone can be added into the atomized liquid, so as to dissolve sputum, reduce and dilute secretions, and achieve the effects of alleviating laryngeal edema and anti-inflammation.

Air embolism is a rare but fatal complication in laparoscopic surgery.^18,19 Two prerequisites should be satisfied for gas to enter blood circulation: first, rupture of noncollapsing veins; and second, pressure difference between gas access and right heart. If the vein is ruptured intraoperatively, air can be absorbed into vein continuously through the rupture under the action of pressure difference. Venous air embolism occurs suddenly, and it is quite severe, which frequently leads to death and severe disability; as a result, prevention is of crucial importance. Indicators for monitoring air embolism under general anesthesia recommended at present include precardial Doppler detector monitoring and continuous monitoring of central venous pressure. Of them, precardial Doppler detector monitoring is one of the most sensitive methods for diagnosing air embolism. ²⁰

Two out of the 81 patients in this group develop CO₂ air embolism intraoperatively. In our opinion, the following several reasons may be responsible for intraoperative air embolism. First, small oral operation space, which leads to local neck vascular avulsion when dilating the approach, and CO₂ enters blood circulation through the ruptured blood vessel. Second, the slightly higher CO₂ pressure injected (8 mmHg) has increased the probability of CO₂ entering blood flow through blood vessel. It has been reported that the risk of air embolism may rise with increased pneumoperitoneum pressure.^21,22 Therefore, we changed the pressure to 4 mmHg in the later stage, and no such complication occurs any longer. The following four suggestions are proposed based on experience of 2 successful rescued cases: (1) get familiar with anatomy of the bottom of the mouth, reinforce basic operation training, and carefully separate connective tissue when dilating space to avoid vascular injury; (2) reduce CO₂ pressure to 4 mmHg and construct surgical space in combination with anterior cervical flap suspension; (3) carry out positive end expiratory pressure to reduce central venous pressure; and (4) carefully intraoperative monitoring, early identification and diagnosis, as well as on time and rapid management to guarantee surgery safety.

Conclusions

The present study highlights that TOET is a safe and effective surgical procedure with less tissue injury along with excellent cosmetic effect. We believe that such an approach will have a broader application in endoscopic thyroid surgery with the continuous accumulation of experience and advance in surgical instrument.