Gastric lymphatic mapping for sentinel node biopsy by natural orifice transluminal endoscopic surgery (NOTES)

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Abstract
Sentinel node biopsy is proposed as sufficiently reliable in determining the lymph node status of early gastric cancer to justify curtailed resection margins if negative. Its performance by natural orifice transluminal endoscopic surgery (NOTES) could therefore expand the patient cohort able to undergo solely endoscopic resection of their primary. A transvaginal NOTES technique was utilized in six pigs (mean weight 30 kg). The posterior colpotomy and pneumoperitoneum was created by a standard double-channel flexible videoendoscope which was then used to perform peritoneoscopy. Concomitant gastroscopy allowed selection of a site along the greater curvature for lymphatic mapping by submucosal injection of methylene blue (3 ml). Furthermore, torque upon this endoscope allowed the posterior surface of the stomach and retrogastric space to become accessible to the transvaginal endoscope. In surveying the mapping in vivo, the intraperitoneal scope could follow blue-stained efferent lymphatic channels to their first-order draining nodes (i.e., sentinel nodes). Conventional instruments worked down the scope's channels were then used to perform the excisional biopsy. At procedure end, the animals underwent immediate laparotomy to ensure the safety and adequacy of the procedure. Each procedure was technically successful. Colpotomy, pneumoperitoneum, and peritoneoscopy were promptly achieved (mean 8 min). Post injection, blue efferent lymphatic channels were immediately appreciable in every animal. Five animals had sentinel nodes in their retropyloric region while the last mapped cephalad towards the esophagogastric junction. Two animals had alternative drainage channels identifying additional sentinel nodes. All blue nodes were dissected cleanly by the intraperitoneal scope and retrieved intact per vaginam. Mean lymphadenectomy time was 19 min. At laparotomy, there was no hematoma, ongoing hemorrhage, or visceral injury in any pig. There were no residual, missed stained nodes or channels. NOTES sentinel node biopsy for the stomach is technically accomplishable in this experimental model. This proof of concept should encourage serious consideration of its applicability to clinical practice.