Peroral endoscopic myotomy (POEM) for achalasia.

Achalasia is an uncommon disorder that results from the degeneration of ganglion cells of the myenteric plexus in the lower esophageal wall. It is manifested by a loss of peristalsis in the lower part of the esophagus and failure of the lower esophageal sphincter (LES) to relax. Peroral endoscopic myotomy (POEM) is a minimally invasive intervention that aims to treat achalasia. It is regarded as the endoscopic equivalent of Heller myotomy. POEM is a form of natural orifice transluminal endoscopic surgery that is completed by creating a submucosal tunnel in the lower part of esophagus to reach the inner circular muscle bundles of the LES to perform myotomy, while preserving the outer longitudinal muscle bundles. The result is decreased resting pressure of the LES, facilitating the passage of ingested material. POEM was initially introduced to treat achalasia by targeting the LES. POEM has expanded to include gastric POEM (G-POEM), myotomy of the pyloric sphincter to treat gastroparesis, and per rectal endoscopic myotomy to treat adult Hirschsprung's disease.