Mediastinoscopic Subaortic and Tracheobronchial Lymph Node Dissection With a New Cervico-Hiatal Crossover Approach in Thiel-Embalmed Cadavers Open Access

We developed a method for performing complete mediastinoscopic esophagectomy as a radical operation via the transcervical and transhiatal approach in 6 Thiel-embalmed human cadavers. The cadavers were donated to the Department of Anatomy, Tokyo Medical and Dental University. Before the patients died, they signed documents agreeing to donate their body for use in clinical studies. The format of the document meets the criteria for the Japanese “Act on Body Donation for Medical and Dental Education.”

All cadavers were embalmed using the method described by Thiel.^5,6  The cadavers were embalmed in a water-based solution consisting of salt with a small amount of formaldehyde for fixation, boric acid for disinfection, glycol, chlorocresol, and ethanol; this precipitation results in tissue homogenization. The skin is life-like, and the joints are fully flexible. We chiefly applied this method for upper mediastinal dissection. The procedures were performed using a pneumoperitoneum apparatus system (Evis Lucera Spectrum WM-NP1; Olympus, Tokyo, Japan). In addition, the thoracic and abdominal aorta was inflated by the agar gel injection method in order to imitate live patient conditions.

The Thiel-embalmed human cadavers were placed in the supine position. For “mediastinoscopic esophagectomy with lymph node dissection” (MELD), two approaches were used: the transhiatal approach and the bilateral transcervical approach. We first performed the transhiatal approach.

Hand-assisted laparoscopic surgery (HALS) was used for gastric conduit mobilization according to the method previously reported.⁷  An upper abdominal incision was created approximately 7 cm for the insertion of the left hand. Then, five 10-mm trocars were inserted into the left subcostal, infraumbilical, left and right lower quadrant of the abdomen following the induction of pneumoperitoneum with CO₂ to a pressure of 10 mmHg (Fig. 1). Gastric mobilization was carried out as in open surgery conserving the right gastroepiploic vessels. Dissection was performed using the ENSEAL (Ethicon Endo-surgery, Cincinnati, Ohio) when needed. The central tendon of the diaphragm was subsequently divided in order to enlarge the hiatus. Then, we used the Lone Star Retractor System (Yufu Itonaga Co Ltd, Tokyo) at the bilateral crura of the diaphragm to obtain a wide view. First, transhiatal dissection was performed between the pericardium and esophagus, then between the aorta and the esophagus, next between the left pleura and the esophagus, and finally the remaining right side of the esophagus was dissected. The pericardium, inferior bilateral pulmonary vein, inferior border of the carina tracheae is clearly exposed and lymph nodes at the bifurcation (107) and left main bronchus (109L) were dissected (Fig. 2).

We now demonstrate the transcervical approach. First, a left cervical collar incision was made and a sufficient working space was made between the tracheoesophageal and the left carotid sheath. Open surgery on the left side was subsequently changed to the pneumomediastinum method after identifying the left recurrent nerve. The Alexis wound retractor (Applied Medical, Rancho Santa Margarita, California) was placed at the above-mentioned space and deployed, a single-port laparoscopic access device (Free Access; Top Corporation, Tokyo, Japan) were attached and three 5-mm trocars were placed in a triangle configuration. A pneumomediastinum was then established with CO₂ to a pressure of 10 mmHg, and the 106recL lymph nodes were dissected along the left common carotid artery, subclavian artery, thoracic duct, and only dorsal area of the left recurrent nerve for the safety of the operation from the right cervical area. We can determine the ramus cardiacus of sympathetic nerve and the thoracic duct (Fig. 3). Finally, the esophageal wall was divided from the membranous trachea in order to be followed by dissection of the 106tbL lymph nodes via the right cervical approach.

Then, a right cervical incision was made, and a flap was created as described for the left side. Open surgery on the right side was changed to the pneumomediastinum method after identifying the right recurrent nerve, similar to that performed on the left side. The right recurrent nerve was dissected, and the ventral side of the right cervical paraesophageal lymph nodes (101R) only was dissected for the safety of the right recurrent nerve. The presence of the right recurrent nerve at the subclavian artery and the region of the right vagus nerve was confirmed. A single-port laparoscopic access device was then placed beneath the above-mentioned area and deployed, and three 5-mm trocars were placed in a triangle configuration, as carried out on the left side. Using the pneumomediastinum method, the 101R and 106recR lymph nodes were dissected along the right mediastinal pleura, proximal portion of azygos vein and right bronchial artery (Fig. 4). The esophagus was dissected from the prevertebral layer in the posterior region, left main bronchus, and aortic arch on the left side.

For dissection of the 106tbL lymph nodes, we used the the “cross-over technique.” First, the front wall of the left main bronchus was dissected and depressed downward using the transhiatal approach, thus obtaining a good view between the aortic arch and cartilage of the left bronchus. The 106tbL lymph nodes were then dissected until the aortic arch was reached (Fig. 5A). Simultaneously, the lymph nodes were dissected via right cervical incisions (Fig. 5B). The left recurrent nerve around the trachea can be observed via the transhiatal approach (Fig. 6). In another case, a mark is left between the aortic arch and left recurrent nerve via the left cervical approach (Fig. 7A). It is possible to detect both the mark and pulmonary artery as well as the left recurrent nerve above the aortic arch via the transhiatal approach (Fig. 7B). The shema is shown in Fig. 7C. Finally, the 106recL lymph nodes on the ventral side were dissected from the left cervical side.

After these operations, I confirm how many lymph nodes dissected in 106tbL area by thoracotomy. It is revealed that these lymph nodes are almost completely dissected in MELD as well as in open esophagectomy and the pulmonary artery, the left recurrent nerve at the aortic arch and the bronchial artery are safely exposed and reserved (Fig. 8).

Conventional transhiatal esophagectomy is recognized as a minimally invasive surgery.^8,9  In this method, the upper mediastinal lymph nodes are usually not dissected. It has traditionally been very difficult to dissect the 106tbL lymph nodes using the mediastinoscopic method because the mediastinal area is narrow and contains very important structures, such as the bilateral main bronchus, recurrent nerve, aortic arch, and pulmonary artery. Previous reports have described the use of mediastinal esophagectomy. For example, Bumm and colleagues recently used an endodissector to eliminate “blind” mediastinal dissection.^10,11  In that method, endodissection is performed via the left cervical approach. At the tip, the instrument provides a tissue dilatator and several openings for the fiber optic bundle, a working channel, and flushing and suction devices. Instruments such as monopolar thermocautery devices, biopsy forceps, and microscissors can be applied through the working channel. Meanwhile, the other team dissects the terminal esophagus from the hiatus and prepares the interposition graft. This method is very convenient and useful for dissecting the esophagus and does not require the use of pneumomediastinum during surgery. However, this method cannot be used to perform complete dissection of the upper mediastinum, including the 106tbL lymph nodes; therefore it is inadequate for upper mediastinum dissection. Tangoku and colleagues reported the application of mediastinoscope-assisted transhiatal esophagectomy (MATHE) with a mediastinoscope and 5-mm-diameter mirror scope attached to a retractor with a transparent flat tip via the left neck.¹²  However, this method is also inadequate for achieving complete upper mediastinum dissection. In another article, the transcervical (left side only) approach with transhiatal esophagectomy using pneumomediastinum for either high-risk patients or for those with early esophageal carcinoma alone.¹³  However, this method is not sufficient for upper mediastinum dissection. Ikeda and colleagues reported the same mediastinum method in which an additional transthoracic procedure is performed, if necessary, for further dissection, including dissection of the lymph nodes.^14,15  Therefore, a transthoracic approach for radical esophagectomy is needed.

We considered whether transhiatal esophagectomy is adequate for radical esophagectomy. Performing transhiatal dissection of the lower mediastinal field is possible, although carrying out such dissection of the upper field is difficult according to conventional methods. Additionally, the degree of motion of the endoscopic forceps suffers from increasing limitations, such as that observed in single-incision laparoscopic surgery (SILS), in which the right- and left-hand devices are parallel to one another. Mori thus reported the use of robotic-assisted transhiatal lymphadenectomy as radical esophagectomy,¹⁶  which can be performed in a few limited institutions. However, we consider that the hiatus of the esophagus should be widely opened in order to improve the surgical view. Therefore, we applied the Lone Star Retractor System to the bilateral crura of the diaphragm. When the bilateral crura are widely opened, the stability of the scope is increased, and the right- and left-hand devices are no longer parallel. It is therefore possible to dissect the 106tbL lymph nodes from the ventral side of the left main bronchus to the aortic arch via the transhiatal approach.

The pneumomediastinum method can be used to enlarge the range of dissection among the bilateral cervical field over that obtained with the transhiatal approach. It is thus possible to dissect the lymph nodes in the area of the left recurrent nerve at the aortic arch via a left cervical incision. Dissection of the 106tbL lymph nodes can be easily performed in the right cervical area. In this region, the adipose tissue adheres only on the caudal side of the aortic arch, as the ventral side of the left main bronchus has already been dissected via the transhiatal approach. We emphasize that obtaining traction for the trachea in the ventral direction from the left cervical area is very important. We named this procedure the “cross-over technique” due to the importance of cooperation in the bilateral cervical and transhiatal area (Fig. 1). We subsequently cut the esophagus in the left cervical area and pulled the tissue in the caudal direction. This demonstrated that the esophagus was totally separated, allowing the lymph nodes, including the 106tbL lymph nodes, to be dissected from the upper to lower mediastinum. Although 3-field lymphadenectomy is needed to perform radical esophagectomy for esophageal cancer, dissecting the 106tbL lymph nodes is very difficult without the use of the transthoracic approach. We herein demonstrated that the “cross-over technique” under pneumomediastinum from the transhiatal and bilateral cervical approach can be applied to dissect the 106tbL lymph nodes relatively easily. The key success factors regarding this treatment modality include 3 points as follows:

1. It is the use of a combined transhiatal and transcervical operation, in which the transhiatally and transcervically lymph nodes are both removed at the same time.

2. It is increasing the size of the mediastinal working space by establishing pneumomediastinum.

3. The 106tbL lymph nodes are dissected from the front wall of the left main bronchus, but not from the dorsal wall of one.

This new method represents a dramatic change in the way of thinking when dissecting the 106tbL lymph nodes.

Using this method, radical esophagectomy can be performed without both robotic procedures and the transthoracic approach. Therefore, a truly minimally invasive procedure for performing radical esophagectomy that does not require transthoracic surgery is now established. We believe that our initial experience with this procedure is a breakthrough that will lead to the development of truly minimally invasive surgery for thoracic esophageal cancer.

We conclude that performing MELD under pneumomediastinum using the bilateral transcervical and transhiatal approach is a useful modality based on our experience with Thiel-embalmed human cadavers.

We thank the staff of Department of Clinical Anatomy for their excellent anatomic assistance. We have no conflicts of interest.