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Thoracoscopic removal of benign esophageal tumors
PRINCIPLES AND JUSTIFICATION
The application of thoracoscopic techniques to the excision of benign esophageal lesions provides a minimal access approach to these lesions that avoids the need for an open thoracotomy incision. Benign esophageal lesions, which are usually leiomyomata, or less commonly esophageal wall (bronchogenic) cysts or gastrointestinal stromal tumors, are found within the esophageal wall musculature. In the case of leiomyoma, the tumor can at times be densely adherent to the underlying esophageal mucosa. Thoracoscopic excision entails dissecting the tumor from the surrounding esophageal wall muscle, while at the same time taking care to avoid opening the mucosa if possible. As this is not always feasible, the mucosa, if breached, can be repaired by thoracoscopic suturing.
The indications for surgical removal of lesions using a thoracoscopic approach include:
- Lesions more than 2 cm in diameter
- Enlarging lesions
- Symptomatic lesions
Malignant transformation in leiomyomata is very rare, and there is no indication for prophylactic removal to prevent this problem.
Before thoracoscopic techniques were developed, it was generally accepted that lesions that exceeded 5 cm in diameter should be removed in fit patients, irrespective of symptoms. However, with the development of less “invasive” thoracoscopic approaches, the size cut-off has been reduced to 2 cm, with lesions less than 2 cm in diameter generally managed conservatively.
Endoscopic ultrasound (EUS) facilitates accurate measurement of size and is the preferred follow-up method. Leiomyomata tend to grow very slowly and often remain stable for many years, but if they enlarge progressively, resection is indicated. Very large tumors require more extensive dissection and may not be suitable for thoracoscopic enucleation.
When tumors exceed 7-8 cm there is a much greater chance that resection will entail esophagectomy. At the other end of the size spectrum, some very small lesions (<1 cm) confined to the submucosal layer of the esophageal wall can be dealt with by endoscopic techniques using an intraluminal approach.
Tumors that cause symptoms such as dysphagia are usually large (>5 cm), whereas smaller tumors are usually asymptomatic. Surgeons need to be aware that dysphagia in patients with a small tumor is often due to a different problem.
PREOPERATIVE ASSESSMENT AND PREPARATION
Patients should undergo full cardiorespiratory evaluation, if necessary with the addition of pulmonary function testing and echocardiography. Patients unsuitable for an open thoracotomy approach should not undergo thoracoscopic surgery, as conversion to an open procedure is occasionally necessary if significant intraoperative difficulties are encountered. Computed tomographic scanning and endoscopy provide important information that helps determine the location of the tumor and ascertains the presence or absence of mucosal involvement or ulceration. If feasible, EUS should also be performed, as it will provide additional diagnostic information and confirm which layers of the esophageal wall are affected. EUS-guided needle biopsy can also be used to obtain a tissue diagnosis, but as the needle crosses the mucosa, needle biopsy can render dissection in the plane between the tumor and mucosa more difficult, thereby increasing the risk of mucosal perforation during surgical enucleation. In addition, as a tissue diagnosis usually does not change surgical decisionmaking, biopsy is probably best avoided in most patients with these tumors. However, if a very large lesion is present and not suitable for enucleation, then needle biopsy can be considered to confirm the diagnosis before esophagectomy.
36.1
Unlike traditional open surgical approaches via a left thoracotomy, thoracoscopic excision can be performed through either a rightor left-sided approach to the esophagus. The choice is determined by the anatomy demonstrated preoperatively by computed tomographic scanning (i.e., if the lesion is in the right esophageal wall, then a right thoracoscopic approach is easiest). For example, for the leiomyoma of the esophagus shown in Figure 36.1, the best access for thoracoscopic excision entailed a right thoracoscopic approach (the arrow shows the direction of access for the endoscopic dissecting instruments). If the tumor is within the anterior or posterior esophageal wall (i.e. potentially suitable for either left or right thoracoscopic resection), the choice of approach is influenced by the proximity of the tumor to the esophageal hiatus and the aortic arch. Distal lesions (within 5 cm of the hiatus) may best be approached from the left, as the elevation of the right hemidiaphragm can restrict access from the right. On the other hand, more proximal lesions are often better accessed from the right side, as the heart and aortic arch can restrict access from the left. From the right side, these structures do not encroach on the operative field.
OPERATION
Anesthesia and position of patient
Two patient positions for thoracoscopic esophageal surgery can be used. Based on open surgical experience, many surgeons position their patients in the lateral position. This necessitates the placement of a double-lumen endotracheal tube to enable the lung to be collapsed. The alternative patient position (which the author prefers) is the prone position. This position provides excellent access to the posterior mediastinum and enables thoracoscopic surgery to be performed without the need for lung retraction. In addition, good access to the esophagus can be obtained in this position using low-pressure (8 mmHg) insufflation of the pleural cavity without collapse of the lung. This allows thoracoscopic surgery to be performed while using a single-lumen endotracheal tube if it is known preoperatively that the lung will not need to be collapsed. Low-pressure insufflation rarely creates anesthetic difficulties. (See Figure 36.2.)
36.2
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