Selective inner muscle layer myotomy is associated with lower pain and same clinical efficacy that full-thickness myotomy in patients treated by POEM for achalasia: A multicenter retrospective comparative analysis of 158 patients

•POEM for achalasia: Selective myotomy targeting inner circular layer equals full thickness in efficacy.•Full thickness myotomy was associated with longer hospital stays and more pain relief use.•No significant difference in reflux rates between selective and full thickness myotomy.•Selective circular myotomy should be preferred over full thickness in POEM for achalasia. The aim of this study was to compare the impact of the depth of myotomy (selective inner layer myotomy (SIM) vs. full-thickness myotomy (FTM)) on the outcome of patients treated with POEM for achalasia. This was a retrospective, observational, conducted in two tertiary centers between October 2018 and September 2022. Patients were divided into two groups: SIM and FTM. The primary endpoint was clinical efficacy at 6 months, while secondary endpoints were postoperative criteria (such as pain, length of hospital stay, complications) and occurrence of gastroesophageal reflux disease (GERD) (esophagitis at 6 months, heartburn, and pH-metry). 158 patients were included in the study (33 in the FTM group and 125 in the SIM group). The success rates at 6 and 12 months were similar in both groups, with 84 % and 70 % in the SIM group versus 90 % and 80 % in the FTM group, respectively (p = 0.57 and p = 0.74). However, more opioid analgesics were consumed in the FTM group compared to the SIM group (41% vs 21 %, p < 0.01). The length of hospitalization was longer in the FTM group than in the SIM group (2.17 ± 2.62 vs 2.94 ± 2.33, p < 0.001). The rate of esophagitis at 6 months was comparable (16 % in the SIM group vs 12 % in the FTM group, p = 0.73). There was no significant difference in terms of heartburn at 6 or 12 months between the SIM and FTM groups (18.5% vs 3.8 %, p = 0.07 and 27% vs 12.5 %, p = 0.35, respectively). There was no significant difference in terms of clinical efficacy and GERD occurrence between FTM and SIM. However, full-thickness myotomy was associated with more postoperative pain and a longer length of hospital stay. Therefore, selective internal myotomy should be preferred over full-thickness myotomy.