Endoscopic intermuscular dissection for rectum-sparing resection of a refractory rectal lesion

Endoscopic intermuscular dissection (EID) is an emerging technique that enables deeper mural resection beyond the submucosa, offering a rectum-sparing approach for fibrotic or superficially invasive rectal lesions. We describe the use of EID after multiple failed EMRs in a patient with a rectal laterally spreading tumor (LST).

A 79-year-old man with a 3-cm rectal LST located 3 cm from the anal verge underwent EID after 4 previous unsuccessful resection attempts. Preprocedural evaluation with narrow-band imaging and indigo carmine chromoendoscopy suggested a fibrotic lesion with possible muscular layer involvement. The procedure was performed with the patient under general anesthesia using a therapeutic gastroscope fitted with a transparent tapered hood, and the saline-immersion technique was used to enhance layer visualization.

After submucosal injection and mucosal incision, a submucosal tunnel was created from the anal side. A targeted myotomy of the inner circular muscle layer exposed the longitudinal muscle, allowing intermuscular dissection. En bloc resection was achieved in 92 minutes. Histopathologic analysis confirmed a tubulovillous adenoma with high-grade dysplasia and R0 resection. The use of the saline-immersion (underwater) technique enhanced visualization of tissue planes and facilitated controlled dissection in the fibrotic area. The patient was discharged the same day without adverse events.

EID enabled curative resection of a fibrotic rectal LST refractory to conventional EMR, and the application of the saline-immersion technique may represent a novel technical modification that improves visualization and safety in challenging fibrotic cases.