The procedure includes four steps: a) a transversal mucosal incision was performed at the proximal antrum. b) a submucosal longitudinal tunnel was created across the pyloric ring. c) full-thickness pyloromyotomy was performed, with a little extension of the antrum. After pyloromyotomy, an ultrathin gastroscope was used to inspect the mucosa and pyloric outlet. d) after careful hemostasis, the mucosal entry was closed by clips.

Per-oral pyloromyotomy (POP), also named as gastric per-oral endoscopic myotomy (G-POEM), for treating infantile hypertrophic pyloric stenosis (IHPS) has the following steps: mucosal incision, creation of submucosal tunnel, full-thickness pyloromyotomy, closure of the mucosal entry.

Primary outcomes included episodes of postoperative vomiting in times.

Primary outcomes included major complication in times (based on lexicon and Clavien-Dindo classification, eg, vital-sign instability, ICU stay, hospital readmission, conversion to laparoscopic or open pyloromyotomy, invasive postoperative procedure, haemorrhage, blood transfusion, or prolonged hospitalization due to functional impairment).

Secondary outcomes included operating and anaesthetic time in minutes.

Secondary outcomes included myotomy length in centimeters