Reply to Yang et al.

We acknowledge Yang et al. for their detailed comments to our recently published paper [1] [2].

We totally agree with Yang et al. that superficial needle insertion and injection can lead to inadvertent intramural esophageal dissection (IED) during peroral endoscopic myotomy (POEM), especially in patients with long-standing achalasia and a thickened esophageal wall. However, the following aspects indicate that the IED in our patient was not caused by the initial superficial injection. First, rapid formation of a bleb toward the lumen was noted after initial injection, which was a reliable sign of good expansion of the submucosal space, as mentioned by Yang et al. [2]. Second, the endoscopic view at initial mucosal incision and at the beginning of tunnel creation were consistent with a regular submucosal layer; thus, the IED in this patient did not develop at the very beginning of the procedure. Third, the unusual-looking visual field developed before we accessed it, and disruption of the muscularis mucosa was noted in this field, so inflation during the procedure and weakness of the muscularis mucosa may be the causes of IED in this case.

In addition, we have further comments about some of the tell-tale signs proposed by Yang et al. First, staining of the tunnel with injection was based on the solution for submucosal injection. We usually add a small amount of methylene blue (≤ 1 mg) to physiological saline (250 mL) for submucosal injection considering the potential harm of submucosal injection of methylene blue [3]. It is unlikely that we would notice obvious staining of the submucosal tunnel using such diluted methylene blue. Second, inadequate expansion of the tunnel with repeated injections may be attributed to submucosal fibrosis, which is more common than IED. According to our experience, this is the first case of IED among all 244 POEM procedures we performed since 2012.

^* Co-first authors.

• References

• 1 Ye L, Jiang J, Ngamruengphong S. et al. Intramural esophageal dissection during peroral endoscopic myotomy. Endoscopy 2019; 51: E197-E198
• 2 Yang D, Draganov PV. Tips and tricks for avoiding the dreaded intramural esophageal dissection during peroral endoscopic myotomy: recognize!. Endoscopy 2019; 51: 996
• 3 Chan EP, Kaltenbach T, Rouse RV. et al. Potential hazards of submucosal injection of methylene blue. Am J Gastroenterol 2012; 107: 633-634