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World J Gastrointest Endosc. Dec 16, 2020; 12(12): 521-531
Published online Dec 16, 2020. doi: 10.4253/wjge.v12.i12.521
Recent advances in third space or intramural endoscopy
Akshay B Shanbhag, Prashanthi N Thota, Madhusudhan R Sanaka
Akshay B Shanbhag, Prashanthi N Thota, Madhusudhan R Sanaka, Department of Gastroenterology, Cleveland Clinic Foundation, Cleveland, OH 44195, United States
Author contributions: Shanbhag AB, Thota PN and Sanaka MR contributed equally to this work; Shanbhag AB, Thota PN and Sanaka MR analyzed the data, wrote and approved the manuscript.
Conflict-of-interest statement: All authors declare no conflict of interest for this article.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Madhusudhan R Sanaka, FACG, FASGE, Director, Department of Gastroenterology, Cleveland Clinic Foundation, 9500 Euclid Ave, Cleveland, OH 44195, United States. sanakam@ccf.org
Received: July 19, 2020
Peer-review started: July 19, 2020
First decision: September 17, 2020
Revised: October 18, 2020
Accepted: November 28, 2020
Article in press: November 28, 2020
Published online: December 16, 2020
Processing time: 146 Days and 13 Hours
Abstract

Third space endoscopy or intramural endoscopy is based on the principle that the deeper layers of the gastrointestinal tract can be accessed by tunneling in the submucosal space and maintaining the integrity of the overlying mucosa. The era of third space endoscopy started with peroral endoscopic myotomy (POEM) for treatment of achalasia and has expanded to treat various other gastrointestinal disorders. The technique is also currently used for treatment of refractory gastroparesis, Zenker’s diverticulum (ZD), resection of subepithelial tumors and early cancers of the gastrointestinal tract and Hirschsprung’s disease (HD). These procedures are rapidly emerging as minimally invasive alternatives to conventional surgery. They are safe and effective with excellent outcomes. This review focuses on the evolution and current applications of third space endoscopy in various gastrointestinal disorders. Key points: (1) Third space or intramural endoscopy initially started with the POEM procedure for treatment of achalasia; (2) Advancements in procedural techniques have expanded its application to treat other gastrointestinal disorders such as refractory gastroparesis, ZD, HD, resection of subepithelial tumors and early gastrointestinal cancers; (3) These procedures are highly effective with excellent outcomes and low complication rates; and (4) Third space endoscopic procedures are rapidly emerging as minimally invasive alternatives to conventional surgery.

Keywords: Third space endoscopy; Peroral endoscopy myotomy; Endoscopic submucosal dissection; Per-oral pyloromyotomy; Per-rectal endoscopic myotomy

Core Tip: Endoscopic techniques and procedures are rapidly evolving with the use of third space endoscopy in various gastrointestinal disorders. Initially starting with the peroral endoscopic myotomy procedure for treatment of achalasia, advances in third space endoscopy have expanded to treat other disorders such as gastroparesis, Zenker’s diverticulum, Hirschsprung’s disease and subepithelial tumors. In this review article, we show how the management of gastrointestinal disorders continues to evolve with third space endoscopy and how various studies have revealed superior outcomes of third space endoscopy when compared to conventional therapy.