The Double Scope Method (DS), performed during peroral endoscopic myotomy (POEM) for esophageal achalasia, is a technique used to objectively confirm complete myotomy of the lower esophageal sphincter (LES). Although several reports have demonstrated the usefulness of DS, no studies have investigated its association with the development of blown-out myotomy (BOM). In this study, we retrospectively evaluated the impact of DS on incomplete LES myotomy and the occurrence of BOM in POEM cases at our institution.

We included 490 patients who underwent POEM at our institution between September 2011 and November 2023 and had at least two years of postoperative follow-up. BOM was defined according to Joseph et al. (GIE 2021) as “a distal esophageal diverticulum corresponding to the previous myotomy site, characterized by a wide opening >2 cm and ≥50% dilation of the esophageal body.” Patients with pre-existing diverticula were excluded. DS was introduced in the 109th case in January 2015 and thereafter performed routinely except in technically difficult cases. Patients were divided into a DS group (n = 380) and a non-DS group (n = 108). We compared the rates of incomplete LES myotomy, overall BOM occurrence, and BOM caused by incomplete LES myotomy between groups. Fisher’s exact test was used for statistical comparisons, with p < 0.05 considered statistically significant.

The success rate of DS was 99.5% (380/382). The rate of incomplete LES myotomy was 0% (0/380) in the DS group and 3.7% (4/108) in the non-DS group, with a significantly lower rate in the DS group (p = 0.002). The incidence of BOM was 0.5% (2/380) in the DS group and 0.9% (1/108) in the non-DS group, with no significant difference (p = 0.53). BOM attributable to incomplete LES myotomy was not observed in the DS group (0%) but occurred in 0.9% (1/108) of the non-DS group; however, this difference was not statistically significant (p = 0.22). No severe adverse events associated with DS were observed.

DS is a reliable technique for objectively confirming complete LES myotomy during POEM, and routine use is advisable. The introduction of DS significantly reduced the incidence of incomplete LES myotomy. Although the overall incidence of BOM in this series was lower than previously reported and statistical significance regarding the impact of DS on BOM occurrence was not demonstrated, the reduction in incomplete LES myotomy suggests that DS may theoretically contribute to preventing BOM. Further accumulation of cases is warranted to clarify this relationship.