To assess intraoperative changes in pyloric distensibility during gastric peroral endoscopic myotomy (G-POEM) using the Functional Lumen Imaging Probe (FLIP), and to determine whether FLIP can provide reliable real-time guidance on the adequacy of pyloromyotomy.

A first analysis of a prospectively maintained G-POEM database was performed (n = 9). FLIP measurements at 50-ml balloon volume were obtained immediately before tunnel creation and after completion of the pyloromyotomy. Recorded parameters included distensibility index (DI, mm²/mmHg), minimal luminal diameter (mm) and cross-sectional area (CSA, mm²). All procedures were performed under total intravenous anesthesia. Adverse events and clinical data were documented. Follow-up at 3–6 months included the Gastric Cardinal Symptom Index (GCSI) and the ¹³C-sodium-octanoate breath test.

The DI increased from a mean of 4.5 to 7.8 mm²/mmHg (Δ +3.3 mm²/mmHg). Minimal diameter increased from 12.8 to 15.2 mm (Δ +2.4 mm), and CSA from 146 to 210 mm² (Δ +64 mm²). No intraoperative complications occurred. Mean procedure time was 78 minutes. In one patient (11.1%), balloon positioning was challenging due to a hook-shaped antrum. Early follow-up data (n = 3) indicate symptomatic improvement accompanied by continued increases in FLIP parameters.

Intraoperative FLIP assessment provides a reproducible, quantitative evaluation of pyloric distensibility during G-POEM. The observed increase in pyloric compliance confirms the technical effectiveness of the myotomy. Early follow-up findings suggest a consistent trend toward clinical improvement and further distensibility gain. FLIP may serve as an intraoperative guidance tool and help determine the adequate extent of pyloromyotomy during the procedure. Further data, particularly long-term correlations and protocol standardization, are required