Mastering the third space: Innovations in intramural endoscopic surgery for gastrointestinal disorders

Table 1 Key differences of peroral endoscopic myotomy procedures

POEM type	Primary Indication	Target anatomy	Submucosal entry point	Myotomy site	Myotomy length
C-POEM	Cricopharyngeal bar/UES dysfunction	Upper esophageal sphincter (cricopharyngeal muscle)	2-3 cm proximal to the cricopharyngeal bar	Cricopharyngeal muscle	Approximately 2 cm
E-POEM	Esophageal achalasia	Esophageal body and LES	10-14 cm proximal to EGJ	Circular ± longitudinal layers of esophagus and LES	7-10 cm
G-POEM	Refractory gastroparesis	Pyloric sphincter	3-5 cm proximal to pylorus	Pyloric muscle ± distal antrum	2-3 cm
Z-POEM	Zenker’s diverticulum	Cricopharyngeal muscle and diverticular septum	3 cm proximal to septum or directly over it	Cricopharyngeal muscle and septum	Approximately 2 cm

All terms have been standardized; and time and distance units have been harmonized for consistency. POEM: Peroral endoscopic myotomy; C: Cricopharyngeal; E: Esophageal; G: Gastric; Z: Zenker.

Table 2 Comparative outcomes of peroral endoscopic myotomy procedures

Poem type	Sample size (range)	Technical success	Clinical success	Adverse events	Follow-up duration
C-POEM	1-27 (mostly case series)	100% (limited data)	100% (largest series)	Approximately 4%-6% (leaks, edema)	Short to mid-term (≤ 12 months)
E-POEM	Dozens to hundreds (multiple studies)	> 95% across studies	Approximately 90%-95%	9%-43% GERD (variable by myotomy length/type)	Up to 5 years in RCTs
G-POEM	30-150 per study (systematic reviews included)	Approximately 95%-100%	Approximately 70%-85% (long-term 76.6%)	5%-10% (bleeding, leak, BAG, dumping)	1-5 years
Z-POEM	30-100+ in comparative studies	Approximately 95%	90%-95%	Approximately 5%-6% (perforation, bleeding)	1-2 years

POEM: Peroral endoscopic myotomy; C: Cricopharyngeal; E: Esophageal; G: Gastric; Z: Zenker; BAG: Bile acid reflux; RCT: Randomized control trial.