Endoscopic Pseudo‐dilation of Esophagogastric Junction During Peroral Endoscopic Myotomy: (With Video)

ABSTRACT Background and Aim During peroral endoscopic myotomy (POEM) for achalasia, endoscopic esophagogastric junction (EGJ) opening is generally considered a sign of successful myotomy. However, in clinical practice, the EGJ may appear to open immediately after submucosal tunneling, even before myotomy is performed. We defined this phenomenon as pseudo‐dilation and evaluated changes in EGJ appearance during POEM. Methods This retrospective study included 65 consecutive patients who underwent POEM between February and June 2025. Endoscopic images obtained at three stages—before POEM, after submucosal tunneling, and after myotomy—were evaluated using a three‐tier Endoscopic Junctional Dilation (EJD) grade. Differences in EJD grade across procedural stages were analyzed using the Friedman test, with post hoc Wilcoxon signed‐rank tests and Bonferroni correction. The Bickenböller statistic was used as a complementary analysis. Two certified endoscopists independently evaluated all images, and interobserver agreement was assessed using Cohen's κ and weighted κ. Results The EJD grade increased significantly after submucosal tunneling compared with before POEM ( p < 0.001). A significant difference was observed between the post‐tunneling and post‐myotomy stages ( p = 0.002); however, most patients showed no change in EJD grade, and the overall distribution of grades remained unchanged ( p = 0.124). Overall, pseudo‐dilation occurred in 95.4% of patients. Interobserver agreement in EJD grade assessment was substantial to perfect across all procedural stages (κ = 0.889; weighted κ = 0.940). Conclusion Pseudo‐dilation of the EGJ was commonly observed immediately after submucosal tunneling during POEM. Trial Registration N/A.