Gastroparesis is a functional disease affecting 4% of the population, which is consecutive to diabetes in 30% of cases and considerably alters the patients' quality of life. The diagnosis is based on gastric fullness symptoms, endoscopy and gastric emptying scintigraphy. The therapeutic alternatives including drug therapies (Metoclopramide, Erythrocin), surgery (Electric gastric stimulation) or endoscopy (Botulinic toxin), are insufficiently effective. Two surgical series suggested an interesting efficacy of laparoscopic pyloroplasty, which remains invasive for a motility disorder. More recently, an US team performed the first case of G-POEM with an excellent outcome and no adverse event. This promising result was confirmed by a Brazilian case, a short retrospective series (7 patients) and the first European case performed and published by our team that has performed 5 cases since. Based on experience, it is proposed a prospective monocentric study to evaluate the efficacy of the G-POEM technique on refractory gastroparesis. This study will include 40 patients on a period of three years, whom suffer from refractory gastroparesis, confirmed by clinical evaluation (GCSI and analogic visual scale), upper GI endoscopy and gastric emptying scintigraphy at the inclusion.