Feasibility of thoracoscopic approach for retrosternal goitre (posterior mediastinal goitre): Personal experiences of 11 cases.

INTRODUCTION: Posterior mediastinal goitres constitute of a unique surgical thyroid disorder that requires expert management. Occasionally, they require thoracic approach for the completion of thyroidectomy. In this paper, we describe the feasibility and utility of a novel thoracoscopic approach for such goitres.
MATERIALS AND METHODS: This is a retrospective study conducted at a tertiary care endocrine surgery department in South India over a period of 5 years from January 2010 to December 2014. We developed a novel thoracoscopic technique for posterior mediastinal goitres instead of a more morbid thoracotomy or sternotomy. All the clinical, investigative, operative, pathological and follow-up data were collected from our prospectively filled database. Statistical analysis was done with SPSS 15.0 version. Descriptive analysis was done. Operative Technique of Thoracoscopic Thyroidectomy: Single lumen endotracheal tube (SLETT) was used of anaesthetic intubation and general inhalational anaesthesia. Operative decubitus was supine with extension and abduction of the ipsilateral arm. Access to mediastinum was obtained by two working ports in the third and fifth intercostal spaces. Mediastinal extension was dissected thoracoscopically and delivered cervically.
RESULTS: Out of 1,446 surgical goitres operated during the study period, 72 (5%) had retrosternal goitre. Also, 27/72 (37.5%) cases had posterior mediastinal extension (PME), out of which 11 cases required thoracic approach. We utilised thoracoscopic technique for these 11 cases. The post-operative course was uneventful with no major morbidity. There was one case of recurrent laryngeal nerve (RLN) injury and hoarseness of voice in the third case. Histopathologies in 10 cases were benign, out of which two had subclinical hyperthyroidism. One case had multifocal papillary microcarcinoma.
CONCLUSIONS: We opine that novel thoracoscopic technique is a feasibly optimal approach for posterior mediastinal goitre, especially for benign and non-invasive malignant goitres.

INTRODUCTION

Nodular thyromegaly is one of the commonest endocrine disorders in India and worldwide.[12] Depending on the definition used for mediastinal goitres, their incidence varies from 1% to 20%.[34] Nodular goitres often require surgical extirpation and most of them can be removed through the cervical approach alone. Less than 5% of the cases require thoracic surgical approach for complete removal of all thyroid nodules.[5] Anterior mediastinal goitres are approached by sternotomy or anterior thoracotomy. Posterior mediastinal goitres usually require posterolateral thoracotomy. All thoracic approaches demand considerable anaesthetic and surgical expertise. In this context, we evaluated our own experience in dealing with thoracic goitres with special emphasis on highlighting the utility of a novel technique of thoracoscopic thyroidectomy for posterior mediastinal extension (PME) of a nodular goitre.

MATERIALS AND METHODS

This is a retrospective study conducted at a tertiary care endocrine surgery department in South India over a period of 5 years from January 2010 to December 2014. We utilised a novel thoracoscopic technique for posterior mediastinal goitres instead of a more morbid thoracotomy or sternotomy. All the clinical, investigative, operative, pathological and follow-up data were collected from our prospectively filled database. Relevant clinical and computed tomography (CT) images of PME goitre are shown in Figures 1 and 2. Statistical analysis was done with SPSS 15.0 (California, Inc) version. Descriptive analysis was done. The study complied with the international ethical norms of the Helsinki Declaration — Ethical Principles for Medical Research Involving Human Subjects, 2004.

Figure 1

Axial CT image of the chest (left) showing right PME; failed intraoperative attempt to deliver PME with finger dissection through the neck (right)

Figure 2

Operative decubitus and port placements - clinical image (left); schematic diagram (right)

We termed our novel technique combined cervical and video-assisted thoracoscopic thyroidectomy (CAVATT). The anaesthetic part of this procedure is termed single lumen endotracheal tube (SLETT). The indication for thoracoscopic approach in our protocol is PME beyond T4 (thoracic vertebral level) with a narrow neck between the cervical and the thoracic components at the thoracic inlet.

Surgical technique of CAVATT

The decubitus of the patient on the operation table is supine extension and abduction of the ipsilateral arm throughout the procedure. General inhalational anaesthesia is utilised. Single lumen reinforced portex endotracheal tube is used for intubation. After draping and sterilising the neck and ipsilateral chest from the posterior axillary line to the opposite midclavicular line, the procedure starts. A long skin crease collar incision is given overlying the goitre in the lower third of the neck. Strap muscles are cut after ligation of the anterior jugular veins. Thyroidectomy of the neck part is performed in the conventional way by mobilising the thyroid gland (TG), ligating the superior, middle and inferior vascular pedicles and saving the external branch of the superior laryngeal nerve (EBSLN) and both sides of the recurrent laryngeal nerve (RLN). We try to deliver the PME through the neck. Only when it is unsuccessful, do we proceed to the thoracoscopic part of the surgery.

A 10-mm port was placed in mid-axillary line of the fourth intercostal space for camera. The pneumothorax was created with CO2 insufflation at a pressure of 6 mmHg and synchronous hypoventilation till adequate working space tantamount to 60% collapse of the ipsilateral lung. Two working ports were placed in the second intercostal space at the anterior axillary line and in the fourth intercostal space 3 cm anterior to the anterior axillary line.

PME is mobilised after dissecting and opening the mediastinal pleura overlying it. Vascular attachments and mediastinal fascia are teased away to free PME within its socket in the posterior mediastinal space. PME is carefully mobilised with a safe distance from the surrounding vital structures, i.e., the superior vena cava (SVC), phrenic nerve, azygos vein, trachea and RLN. PME is delivered in continuity with the neck goitre to the neck. Total thyroidectomy is completed through the neck. After securing haemostasis, the intercostal drain is placed, lung expansion is checked and the port wounds are closed. The schematic diagram and operative pictures of the procedure are shown in Figures 3 and 4.

Figure 3

Intraoperative thoracoscopic views – operative (left); schematic (right) showing A: SVC, B: Phrenic nerve, C: Azygos vein, D: Collapsed upper lobe of the right lung, E: PME of goitre

Figure 4

Gross ex vivo specimen – arrows pointing to PME into the chest after total thyroidectomy

Special note on pre-operative and post-operative care

The pre-operative preparation starts with workup and management plan. Thorough clinical evaluation is carried out to evaluate the pressure effects of goitre (potential or overt) and the extent of goitre. Thyroid function test is used to establish euthyroidism or to find the severity of hypothyroidism; in other words, hyperthyroidism is the initial step. Cross-sectional imaging with contrast-enhanced computerised tomography (CECT) scan in the axial, coronal and sagittal sections from the base of the skull to the D8 level is vital in operative planning. X-rays of the chest and neck [anterior-posterior (AP) and lateral views] to assess the tracheal architecture are important from the anaesthetic and post-operative tracheomalacia point of view. Routine investigations (haematology and clinical chemistry) and cardiac, pulmonary and metabolic assessments are carried out as with any other major general surgical case. The duration of surgical timing depends on the severity of the pressure symptoms, respiratory effects and functionality (hyper- or hyperthyroidism). Pre-operative chest physiotherapy and incentive spirometry, apart from optimisation of comorbidities (glycaemic, normotensive, haematological, coagulative and cardiac profiles), constitute the cornerstone of surgical success. Informed consent from the patients; thorough pre-anaesthetic assessment; surgeon-anaesthetic discussion on the need for intubation, extubation and tracheostomy; theatre readiness with sternotomy, thoracotomy, thoracoscopic equipment; and access to blood transfusion products are the commandments for an optimal outcome of CAVATT.

RESULTS

During the study period of 5 years, 1,446 cases of surgical goitres were treated/operated by the first author in endocrine surgery departments at two tertiary care institutes in South India. All malignant and diffuse toxic goitres were excluded and only clinically non-toxic nodular goitres were considered in this study. Of them, 72/1,446 (5%) cases had mediastinal extension qualifying for retrosternal or thoracic goitre. For the purpose of this paper, we are using the terms mediastinal goitre, PME and anterior mediastinal extension (AME) from hereon. Notably, 45/72 (62.5%) cases had AME with 14 cases on the right side, three in the midline and 28 on the left side. Only 4/45 (8%) AME cases required extracervical approach, out of which three sternotomies and one claviculotomy were carried out, along with access to the neck. One patient had sternal dehiscence with mediastinitis. Notably, 27/72 (37.5%) cases had PME with 25 on the right side and two on the left side. Also, 11/27 PMEs required thoracic approach for whom CAVATT was utilised. The rest of the 16 PMEs could be operated through the cervical approach alone. The mean age of the cohort was 51.5 ± 11.5 years (range: 34-67 years). Average duration of the goitre was 31.7 ± 14.6 months (range: 8-72 months). The clinicoinvestigative details are displayed in Table 1. Operative time of CAVATT was 179.5 ± 23.5 min (range: 140-225 min). Average operative blood loss was 85 ± 25 mL (range: 60-230 mL). The fourth and seventh cases required elective tracheostomy and delayed extubation for tracheomalacia. The operative details are elaborated in Table 2.

Table 1

Clinicoinvestigative profile of patients undergoing CAVATT

Table 2

Operative, post-operative and follow-up details

All the patients were encouraged early ambulation and they returned to normal activity and diet within 2 days (day 1-3). The intercostal drain was removed on the fourth or fifth post-operative day after confirming complete lung expansion and ruling out pleural effusion with x-ray of the chest. Majority of the patients (87.5%) were discharged by the sixth post-operative day. In this study group, there was no mortality. The post-operative course was uneventful with no pulmonary and surgical morbidities. There were no incidents of atelectasis, consolidation, or chest infection. There was one case of RLN injury and hoarseness of voice in the third case, probably due to thermal injury to the thoracic loop of RLN during thoracic dissection of PME. Histopathologies in 10 cases were benign (colloid goitre: Five; adenomatous nodules: Three; and colloid goitre with Hashimoto's thyroiditis foci: Two), out of which two had subclinical hyperthyroidism. One case had multifocal papillary microcarcinoma. None of the cases had soft tissue and vascular or cartilage invasion but two had thick adhesions probably due to Hashimoto's thyroiditis component. The mean follow-up duration was 31.6 ± 4.2 months (range: 6-62 months). Figure 1 shows radiological view. Figures 1–3 illustrates intraoperative details and retrieved specimen images are shown in Figure 4.

DISCUSSION

Incidence of nodular goitres of the thyroid is as high as 5-12% in large population studies both in the developing world and the Western world.[12] As the size of goitre increases, depending on neck anatomy and direction of nodular growth, some of them extend to the thorax becoming a mediastinal goitre. The incidence of mediastinal goitres (retrosternal goitres) are quoted over a wide range from less than 1% to 20%[34] in the literature due to multiple definitions on its extent. Nodular goitres often require surgical extirpation and most of them can be removed through the cervical approach alone. Less than 5% of the cases require thoracic surgical approach for complete removal of all thyroid nodules[5] though a few series have quoted higher rates of thoracic approach.[6] Though the surgical indications for extracervical approach are variedly mentioned in the literature, the underlying message is the inability to deliver PME safely through neck incision alone. Accordingly, though our indication for thoracoscopic approach is PME beyond T4 with narrow neck between the cervical and thoracic components at the thoracic inlet, we do try to deliver the thoracic goitre via the neck in all cases before resorting to CAVATT. The utility of this criterion aids us in being prepared for the thoracoscopic approach. The manoeuvre that we use to deliver PME is identifying the RLN, incising ligaments in the sternal notch, teasing of the pre-tracheal fascia and gentle manipulation of the goitre staying anterior to RLN (pushing rather pulling). Whenever undue force is required or resistance is encountered or bleeding from an unknown source occurs during the delivery of PME into the neck, we abandon and resort to CAVATT. Anterior mediastinal goitres are approached by claviculotomy, sternotomy, or anterior thoracotomy.[5] Posterior mediastinal goitres usually require posterolateral thoracotomy.[7] All thoracic approaches demand considerable anaesthetic and surgical expertise.[8] Sternotomy is associated with both short-term and long-term morbidities in a considerable proportion of the cases.[9] We even had sternal dehiscence with mediastinitis in one of the cases of the sternotomy group. Conventional anaesthesia for thoracotomy usually necessitates double lumen endotracheal tube with single lung ventilation, which is associated with significant pulmonary morbidity and is expensive too.[1011]

PME can be operated by sternotomy (partial or total), claviculotomy, anterior thoracotomy, posterolateral thoracotomy, or by video-assisted thoracoscopy.[5] Combined cervical, thoracotomy and thoracoscopy approach were utilised for successful intrathoracic goitre delivery in large PME or composite mediastinal goitres. Further, total lung collapse and hypoventilation in single lung ventilation may lead to post-operative atelectasis and hypoxia, especially in the elderly and those with pre-existing lung disease.[811] Thoracoscopic surgery using SLETT was successfully employed in various procedures of esophagectomy, lobectomy, mediastinal biopsy and empyema.[12] Robotic thoracoscopic thyroidectomy was done in quite a few centres and appears to be a promising development but is very expensive and not available or affordable to the majority of our patients.[13]

In this study, partial lung collapse under carbothorax was enough for this technique. We did not use more than 6 mmHg, which is enough to expose PME by collapsing the upper lobe and part of the middle and lower lobes of the lung. Apart from technical and evidential basis, financial concerns instigated us to innovate a cost-effective approach such as CAVATT for PME. In developing countries, thoracic approach under single lung ventilation is an expensive ordeal for most patients. To put it more accurately, each CAVATT procedure till the discharge of the patient on an average was 80,000 while thoracotomy under single lung ventilation costs more than 100,000 for surgery alone. Post-operative care and medications are additional. More hospital stay and any pulmonary morbidity will increase the expenses to the prohibitive level. The advantages of using CAVATT are routine anaesthetic expertise and lower cost as it avoids costly equipment and medications needed to maintain and reverse single lung ventilation. Moreover, placing the patient in a supine posture during the entire procedure prevents any malposition of the endotracheal tube due to frequent movement/tilting of the patients for thoracotomy. These technical and ergonomical simplicities significantly reduce the operating time. Thoracoscopic dissection ensures delivery of the goitre under magnified vision without the fear of bleeding or damage to vital mediastinal structures such as the phrenic nerve, azygos vein, posterior intercostal vessels, or aberrant vasculature due to blind finger dissection during conventional neck approach. We found very scant studies on thoracoscopic approach for thyroidectomy in spite of its obvious advantages. Anectodatal reports of mediastinoscopy, in addition to cervical approach for PME, were found to be reported.[14] As this procedure is carried out with partial lung collapse, major ventilation-perfusion mismatch and its attendant morbidity are obviated.[15]

We did not have any left-sided PME large enough to warrant CAVATT. Probably, the aortic arch toward the left paramedian position resists PME, facilitating its preferential dextrotropism. On the contrary, AME is more common on the left than the right side due to a more capacious anterior mediastinum on the left side, anterosuperior to the aortic arch. Even our data justify this hypothesis of mediastinal structural anatomy guiding mediastinal direction of thoracic goitres. As we see in these data, AMEs are twice more common on the left side and PMEs are predominantly on the right side. Due to this skewed distribution, we cannot comment on the technical aspects of CAVATT for left-sided PME. But we opine that it is equally feasible on the left side as in the case of video-assisted thoracic surgery (VATS) thymectomy. We consider invasive thyroid cancer as the only contraindication for this procedure.

CONCLUSION

This novel thoracoscopic technique appears to be an optimal approach for posterior mediastinal goitre.

Thoracoscopic approach for PME presents a feasible alternative to conventional open approaches such as sternotomy or thoractomy due to its safety and simplicity. Proper case selection, expertise in minimal access surgery and extensive experience in thyroid surgery are keys to the success of this surgery.

Financial Support and Sponsorship

Nil.

Conflicts of Interest

There are no conflicts of interest.