Abstract
Third space or submucosal space is a potential space which on expansion allows the
endoscopist to execute a multitude of therapeutic procedures for various gastrointestinal
diseases like achalasia, subepithelial tumors, Zenker’s diverticulum, and refractory
gastroparesis. Third space was first utilized for performing endoscopic myotomy in
cases with achalasia cardia about a decade ago. Since then, the field of submucosal
endoscopy has witnessed an exponential growth. The present review focuses on recent
advances in the field of third-space endoscopy. With regard to per-oral endoscopic
myotomy (POEM) in achalasia cardia, several recent studies have evaluated the long-term
outcomes of POEM, compared endoscopic myotomy with pneumatic dilatation (PD) and surgical
myotomy, and evaluated the outcomes of short- versus long-esophageal myotomy. In addition,
the utility of multiple dose antibiotic prophylaxis to prevent infections after POEM
has been questioned. Overall, the results from these studies indicate that POEM is
a durable treatment modality, equally effective to Heller’s myotomy and superior to
PD. With regard to gastric-POEM (G-POEM), recent studies suggest only modest efficacy
in cases with refractory gastroparesis. Therefore, quality studies are required to
identify predictors of response to optimize the outcomes of G-POEM in these cases.
Another third-space endoscopy procedure that has gained popularity is endoscopic division
of septum in cases with esophageal diverticula including Zenker’s POEM and epiphrenic
diverticula POEM (Z-POEM and D-POEM, respectively). The technique of diverticulotomy
using the principles of submucosal endoscopy appears safe and effective in short term.
Data on term outcomes are awaited and comparative trials with flexible endoscopic
myotomy required. Per-rectal endoscopic myotomy (PREM) is the most recent addition
to third space endoscopy procedures for the management of short-segment Hirschsprung’s
disease. Limited data suggest that PREM may be a promising alternative surgery in
these cases. However, quality studies with long-term follow-up are required to validate
the outcomes of PREM.
Keywords
submucosal endoscopy - achalasia - gastroparesis - Zenker’s diverticulum
