Peranal Endoscopic Myectomy for Lower Rectal Lesions with Severe Fibrosis: A Retrospective Study

Peranal endoscopic myectomy (PAEM), also known as endoscopic intermuscular dissection, enables resection of lower rectal lesions with severe submucosal fibrosis by dissecting the inner circular muscle. We aimed to evaluate the efficacy and safety of PAEM.

This retrospective study included patients who underwent PAEM for lower rectal lesions between January 2017 and December 2024 at the Osaka International Cancer Institute. PAEM was performed intentionally after October 2023, whereas unintentional PAEM occurred during endoscopic submucosal dissection (ESD) prior to October 2023. Short-term outcomes were assessed, and negative vertical margin rates were compared between groups.

Among 242 consecutive patients who underwent ESD for lower rectal lesions, PAEM was performed in 25 patients (unintentional PAEM, 13; intentional PAEM, 12). The median age was 66 years (range, 38-89 years), and 14 patients (56%) were female. En bloc resection was performed for all 25 lesions. Histological examinations showed 19 adenocarcinomas (pTis, 3; pT1, 11; pT2, 5), 3 other tumors, and 3 non-residual tumors (salvage treatment after endoscopic resection). After PAEM, hematochezia occurred in 14 patients (56%), but most cases were self-limited and one patient had hematochezia requiring prolonged hospitalization. The negative vertical margin rate was higher in the intentional PAEM group than in the unintentional PAEM group, with similar findings observed in an additional analysis excluding salvage cases (88% vs. 33%, P = 0.007).

PAEM was feasible and generally safe. Intentional PAEM may facilitate vertical margin control in selected cases with severe fibrosis.