Analysis of factors associated with operative difficulty in thoracoscopic esophageal cancer surgery in the left-decubitus position: a single-center retrospective study

Our findings showed the importance of the positional relationships of intrathoracic organs with intraoperative injury and postoperative complications in MIE performed in the LDP. Previously, it has been reported that smoking history, comorbidities, operation time, and intraoperative blood loss are important factors associated with the postoperative complications after esophagectomy [11‐14]. In recent years, MIE has been induced in many institutions and its effectiveness and less invasiveness have been reported worldwide [5, 14, 15]. In esophageal cancer surgery, thorough mediastinal lymph node dissection is essential, with the left wall of the aorta and left mediastinal pleura chosen as the left border and the anterior surface of the aorta and vertebral body chosen as the dorsal border [5]. However, in clinical practice, we have often experienced procedural difficulties and an increase in intrathoracic operation time in MIE performed in patients with a narrow mediastinal space. In cases with a narrow mediastinal space and deep aorta, our experience has shown that the external force needed to manipulate the surrounding organs often increases because of the difficulty in obtaining a good operative field that enables a thorough mediastinal lymph node dissection. Even if enough lung collapse is achieved by performing isolated lung ventilation during MIE in the LDP, the procedure is greatly affected by the anatomical position and movements of the intrathoracic organs due to the compression and traction performed by the assistant. Consequently, intraoperative direct injury to the lung surface and mediastinal tissues by the retractor or the operator’s forceps can occur.

Only a few reports have demonstrated a mathematical correlation between procedural difficulty and intrathoracic anatomical features. Fujiwara et al. and Okamura et al. reported technical difficulties in performing MIE caused by the position of the descending aorta or width of the mediastinal space, which were related to the ventral–dorsal distance between the sternum and vertebra [7, 16]. Uchihara et al. reported that a left-sided esophagus can increase the MIE procedural difficulty and postoperative incidence of morbidity in the LDP [6]. Especially in patients with a narrow mediastinum and deep esophagus, it is assumed that the quality of the surgical technique is greatly affected by the ability of the assistant to maintain a good view of the operative field of the mediastinum by manipulating the organs. Additionally, procedures involving the mediastinal organs or vessels that are performed in a poor operative field can cause organ injury or bleeding. Contusions of the lung surface and internal damage caused by excessive external force against the lung, trachea, and bronchus caused by a retractor are thought to cause injuries that can lead to postoperative pneumonia and sputum expectoration disorder. Therefore, it is suggested that minimizing compression and retraction manipulations may reduce respiratory complications. In fact, the α value, which is an indicator of deep aorta, and the β value, which is an indicator of distant aorta, are significantly associated with intraoperative organ injuries, so the importance of these anatomical indices cannot be ignored. We believe that the distant aorta indicates the distant periesophageal tissue to be dissected. We have performed MIE with artificial pneumothorax by CO₂ insufflation to protect the right lung from the potential damage caused by the forceps and retractor. In our experience, intrathoracic CO₂ insufflation itself is theoretically beneficial to make a satisfactory operative field and reduce intrathoracic blood loss and secondary organ injury in the LDP [9]. It has been reported that physical characteristics, including a left-sided esophagus and strong lordosis, can correlate with aging and cardiovascular or pulmonary comorbidities and the onset of pulmonary complications after esophagectomy [6, 12, 17, 18]. Okamura, et al. reported that there was a significant correlation between the intraoperative time with the tumor depth, the presence of NAC, thoracic duct resection, and intrathoracic blood loss [16]. In addition, Guo et al. have reported that unplanned intraoperative events such as bleeding, intrathoracic adhesions, and serious tumor invasion that could not be anticipated preoperatively could be risk factors of postoperative pulmonary complications and chylothorax [19]. And inflammation, local edema, and sclerotic changes in the mediastinum following neoadjuvant chemoradiotherapy can increase intraoperative tracheal injury [20]. In our experience, we have sometimes encountered procedural difficulty in highly advanced cases, but cT, cN, cM, cStage, the presence of NAC, and tumor resectability were not independent predictive factors of intraoperative organ injury. On the other hand, conversion to open thoracotomy was frequently observed in the patients with longer α and shorter β. This finding means that secondary injury itself is frequent in patients with a shallow and non-distant aorta. It is possible that forceps tend to stick into the aortic wall, so care should be given to the usage and vector of the right-hand forceps.

To minimize the influences of a deep and distant aorta, narrow mediastinum, and presence of the right lung, MIE in the prone position has become popular in recent years [21‐23]. Otsubo et al. reported that MIE in the prone position is more effective for improving postoperative oxygenation and reducing pulmonary complications than MIE in the LDP [22]. In the prone position, even with double-lung ventilation, the heart, lung, and esophagus are pulled downward by gravity, and it is possible to maintain a better operative field view without the need for the assistant to retract the right lung and because blood pools to the bottom of the mediastinum [23, 24]. Operating on the dorsal side of patients may present several challenges due to poor ergonomics and an increased risk of intraoperative events. Alternatively, conducting the operation on the ventral side of the patient with a prone or semi-prone position might be more suitable for dissection of the mid-to-lower thoracic esophagus. In cases where dissection involves the recurrent laryngeal nerve, both dorsal and ventral stances should be considered viable options. In addition, the anteroposterior distance may be longer in the mediastinum than in the LDP. Higuchi et al. reported that it is possible to predict the intrathoracic procedural difficulty by performing a preoperative CT scan in the prone position [25].

Furthermore, robotic surgery technology has been recently introduced for esophageal cancer surgery and is gradually becoming popular worldwide [26, 27]. By making good use of the multi-joint function of robotic arms, it is possible for a surgeon to gently manipulate organs and tissues during mediastinal dissection and maintain the operative field by themselves and may alleviate the procedural difficulty of MIE. On the other hand, transmediastinal surgery can also resolve this problem. Yoshimura et al. reported that postoperative pneumonia was significantly decreased in transmediastinal esophagectomy relative to that in transthoracic esophagectomy (0% vs. 24.3%; P = 0.008) [28]. Compared with transthoracic esophagectomy, transmediastinal esophagectomy may place less stress on the thoracic organs and not be affected by deep and distant esophagectomy. It is suggested that advances in devices and surgical techniques may eventually contribute to further development of esophageal cancer surgery.

There were several limitations in this retrospective study because of several influential factors, such as the surgeons’ and assistants’ proficiency, the use of artificial pneumothorax, and the stage of esophageal cancer. In addition, the preoperative CT imaging was performed in the supine patient position, which differs from the actual patient position, such as the LDP or prone position. However, we believe that the anatomical features obtained from preoperative CT in the supine position undoubtedly reflect the degree of procedural difficulty of MIE. From our results of the present study, we suggest setting the position of the surgeon’s right-hand port more cranial or more ventral in cases with deep or distant aorta and narrow mediastinum in order to reduce the difficulty of surgical procedures of MIE. And we also suggest selecting the prone position and using the artificial pneumothorax to reduce the influences of the narrow mediastinum and the presence of the right lung in order.