Blown-out myotomy: emerging phenotype in post-myotomy failure after POEM and Heller myotomy.

Blown-out myotomy (BOM) is an underrecognized but increasingly acknowledged long-term structural complication following both laparoscopic Heller myotomy (LHM) and peroral endoscopic myotomy (POEM) for achalasia. Characterized by a localized pseudo-diverticulum or eccentric dilation at the prior myotomy site, BOM often manifests with recurrent dysphagia, regurgitation, and food stasis, and may mimic treatment failure or other anatomic abnormalities. Radiologically, BOM is defined as a > 50% increase in distal esophageal diameter, best visualized on barium esophagogram, with corresponding endoscopic findings including mucosal outpouching or septum formation. The true incidence of BOM is likely underestimated but recent studies report rates ranging from 18 to 30%. Although some cases may remain asymptomatic, BOM is increasingly recognized as a significant contributor to late symptom recurrence post-myotomy and may account for up to a quarter of post-POEM failures. Diagnosis requires a multimodal approach including barium imaging, endoscopy, high-resolution manometry, and EndoFLIP. Management is individualized and ranges from conservative strategies to re-do POEM with diverticulotomy and, in severe cases, surgical intervention such as esophagectomy. Emerging tools like FLIP panometry may provide superior assessment of distensibility, improving both diagnosis and therapeutic planning. Increased awareness and standardization of diagnostic criteria are essential to identify BOM early and guide appropriate intervention, thereby improving long-term outcomes. This review aims to summarise current knowledge on the definition, pathophysiology, diagnostic criteria, clinical relevance, and therapeutic approaches to BOM.