Many studies have described MIE based on traditional parenchymal organ anatomy. This is the first study to describe MIE with a focus on PEL anatomy. Human lacuna anatomical study indicates that the PEL is a kind of soft tissue lacuna that is usually filled with loose connective tissue, nerves, blood vessels and lymphangion. Esophagectomy aims to achieve radical tumor resection and should also guarantee patient safety. For this to occur, the tissues and organs of the PEL should be properly treated during esophageal mobilization. These tissues and organs include the vagus nerve, bilateral RLNs, bilateral bronchial arteries, the azygos vein arch, the thoracic duct and the lymph nodes around the esophagus (group 2R, 2L, 4R, 7, 8U, 8M, 8L, 9R, 10R and 15 (AJCC & UICC)) [15, 16].
Combining published work on human lacuna anatomy with our clinical practice has enabled us to design a practical method for esophagus dissection. First, we chose to use the left lateral decubitus rather than the prone position [17–19], which was based on our experience in open esophagectomy. In the left lateral prone positon, it is difficult to mobilize the esophagus if it is located on the left side of the thoracic aorta, and sheltered by the spine and aorta. In the left lateral position with the bed inclined forward 30 degrees, we had good surgical vision and avoided this esophageal sheltering [20–23]. For clearer exposure of PEL tissues such as the nourishing arteries, nerves and lymph nodes, an artificial pneumothorax was used to expand the PEL facilitating radical resection and improving surgical safety [12, 24–26]. This is consistent with the role of an artificial pneumoperitoneum in surgeries involving the liver, stomach, intestine and kidney [8, 12, 13, 27]. Finally, we designed a sequence for dissection of different parts of the PEL. The middle and lower PEL (below the azygos vein arch) was dissected prior to the upper PEL (above the azygos vein arch), because the middle and lower PEL were bigger than the upper PEL. Several nourishing esophageal arteries in the posterior PEL (between the esophagus and spine) arise from the thoracic aorta. We dissected the posterior PEL before the anterior PEL (between the esophagus and pericardium) to decrease the possibility of bleeding.
After transection of the azygos vein arch, mobilization of the esophagus at its left side became easier while pulling up the gastric conduit in the following steps became safer. After ligation of the bilateral bronchial arteries, bleeding during dissection of the subcarinal lymph nodes and accidental bleeding after surgery would both decrease. We kept the lung branches of the vagus nerve to decrease posterior pulmonary complications. We avoided using electrically powered instruments near the RLNs to decrease posterior hoarseness. We preferred to modularly dissect lymph nodes in the PEL. We dissected some groups of esophageal lymph nodes including group 8M, 8L, 9R and 15 (Module 1) and group 8U and 4R (Module 2), which were easier than other groups of lymph nodes (Module 3, group 2R and Module 4, group 7). The most difficult procedure was to expose the left RLN, so we dissected lymph nodes along the left RLN (Module 5, group 2L) at the last step.
In our series of 147 consecutive patients, thoracoscopic esophagectomy was shown to be feasible with (group 2) or without (group 1) expanding the peri-esophageal space. Most operation features were better in group 2, while most postoperative complications were similar in the two groups. This showed that expanding the peri-esophageal space facilitates mobilization of the esophagus and dissection of the lymph nodes within mediastinum. The higher frequency of hoarseness complications in group 2 was thought to be because more lymph nodes were dissected in this group with the possibility of more nerve injury during lymph node dissection along both RLNs. The survival curve showed that one-year and three-year survival rates were better in group 2 although this was not statistically significant.
Our study has some limitations. First, we had a relatively small population in our study. Second, there were more patients with non-squamous carcinoma and more advanced disease staging in group 1. Third, more operations were performed earlier in group 1 than in group 2. Fourth, the surgeons’ experience might lead to bias. However, other studies have also shown advantages in terms of visibility and accessibility of the surgical field, with better subsequent surgical outcomes by expanding the PEL .