MRI lymphography for esophageal sentinel node mapping: evolution of a NOTES technique
Epublication WebSurg.com, Mar 2011;11(03). URL: http://websurg.com/doi/vd01en2993
Introduction: Natural Orifice Transluminal Endoscopic Surgery (NOTES) may render conventionally inaccessible anatomic sites accessible in a truly minimally invasive means. Having developed expertise in esophageal mural tunneling for the purposes of endoscopic Heller’s myotomy, we now cautiously explore the feasibility of a transesophageal technique for sentinel node mapping based on MRI lymphography. Methods: two non-survival porcine models were used to demonstrate how targeted mediastinal lymph node biopsy could be performed transesophageally by a combination of endoscopic submucosal lymphatic mapping, MRI imaging and NOTES. First, lymphatic mapping of the area of interest is performed by injecting 2mls of methylene blue submucosally using a standard gastroscope inserted into the distal esophagus. This suspension of small molecular size dye particles is rapidly taken up by the submucosal lymphatic efferents and transported to the first echelon draining lymph nodes which are then detectable by their blue discoloration. After a few minutes, the endoscope is withdrawn proximally to this injection site and a mucosal incision made 15cm from the EGJ to allow creation of a submucosal tunnel using a biliary soft tipped dilatation balloon. This along with the pressure of endoscopic CO2 insufflation allows a space to be formed within the esophageal wall. A second staggered incision then allows exit of the endoscope into the mediastinum proper. Once in this anatomic space, a careful search is performed for blue discolored lymph nodes whereupon standard endoscopic dissection instruments allows selective lymphadenectomy to be performed and the salient nodes withdrawn to the exterior via to esophagotomy. The small diameter of the scope allows for easy retroflection providing good visualization even of the proximal esophagus. The last step is mucosal clip closure to reinforce the mucosal flap seal. The retrieved nodes were MRI scanned to confirm the presence of gadolinium in the dyed nodes. In the second animal the mapping was performed as described above but instead of retrieving only the sentinel nodes an en bloc esophagogastrectomy was performed to assess the sentinel nodes basin distribution at MRI. Results: The operative technique proved readily feasible in all its aspects with blue sentinel nodes being found around the distal esophagus. The gadolinium combined with methylene blue was found in the first draining nodes in both animals. Conclusions: MRI imaging may provide a new tool for sentinel node basin identification, and if proved sufficiently reliable, may represent a step further towards a solely endoscopic diagnosis and resection of the primary tumor.