Transesophageal Mediastinal Lymph Node Sampling.

1. Objective of the study: Improved minimally invasive lymph node sampling for cancer staging and diagnosis of mediastinal lymphadenopathy is desirable. Natural orifice approaches may offer improved minimally invasive options. We have previously reported on the technical feasibility and the potential low risk of transesophageal mediastinoscopy using the submucosal endoscopy with mucosal flap safety valve (SEMF) technique. In this study we evaluated the technical feasibility and safety of transesophageal mediastinal lymph node sampling.
2. Description of the methods: 2 week survival study with 4 domestic pigs. Under general anesthesia, mediastinal lymph nodes were identified by endoscopic ultrasound (EUS) and by marked with a sterile carbon particle solution by transesophageal FNA. A standard diagnostic endoscope was then advanced into the esophagus. High-pressure carbon dioxide submucosal injection followed by balloon dissection created a submucosal working space for insertion of a cap-fitted endoscope. Snare resection of the muscularis propria at the distal end of the submucosal tunnel allowed entrance into the mediastinum. Marked lymph nodes were identified by pararotic and paraesophageal dissection and either sampled with biopsy forceps or removed by snare. The muscular defect was sealed with the overlying mucosal flap, and the offset mucosal entry site was closed with clips.
3. Preliminary results: Lymph nodes were located and harvested in three pigs. The fourth animal was euthanized due to intraoperative respiratory distress. Harvested tissue was pathologically verified as nodal tissue and revealed inflammatory changes in 2 of the 3 animals. Endoscopy and necropsy were performed 2 weeks after the procedure. The SEMF technique provided successful access to the posterior mediastinum in all animals. Two pigs survived 2 weeks without clinical complications, and the defects were completely sealed by the mucosal flap. One of these animals had an asymptomatic mediastinal abscess. The third animal expired in the immediate post-operative period. Identification of lymph nodes was difficult in this animal prolonging the procedure. Necropsy of the two deceased animals did not reveal an operative cause of death.
4. Conclusions: Transesophageal mediastinal lymph node sampling using the SEMF technique proved feasible. Mechanical ventilation is required intraoperatively to prevent respiratory related morbidity. Discerning marked lymph nodes from vascular structures was challenging due to blue/black marking. New labeling techniques would improve the efficiency and safety of this procedure. Further refinement of this technique may advance cancer staging and diagnosis of lymphadenopathy by offering efficient, safe, minimally invasive tissue harvest.

Session: Poster

Program Number: P266

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