Submucosal tunneling endoscopic resection technique with intermuscular dissection for a rectal gastrointestinal stromal tumor

A 54-year-old woman was referred to our center for evaluation of a subepithelial tumor located in the posterior wall of the rectum, 1 cm proximal to the anal verge. Endoscopic ultrasonography showed a 15-mm hypoechoic homogeneous submucosal lesion. Submucosal tunneling endoscopic resection (STER) was performed (Video 1) under monitored anesthesia care, using CO2 insufflation, a standard gastroscope (GIF-H190) with a transparent cap (D-201-10704), DualKnife J 1.5 mm (Olympus, Tokyo, Japan), and a VIO 200D (Erbe, Tübingen, Germany). The submucosal lift was achieved with a mixture of saline solution and indigo carmine. A small horizontal incision was made at the distal margin and a submucosal pocket was created. After dissecting the subepithelial tumor from the submucosa (Fig. 1), an intermuscular dissection assisted by a water-jet injection into the intermuscular space was performed (Fig. 2, Fig. 3). Finally, the larger vessels were coagulated with a bipolar forceps (HS-D2622; Pentax, Tokyo, Japan) and the mucosal defect was closed with four 11-mm through-the-scope clips (MED-204-CLP; Meditalia, Palermo, Italy). The technical duration of the procedure was 30 minutes. The patient was discharged 2 hours later with the indication to take prophylactic oral antibiotic therapy for 5 days. No complications were reported. Histology showed a 12-mm gastrointestinal stromal tumor (GIST) surrounded by thin smooth tissue, with free margins (R0) and mitotic index <5/mm2 (Fig. 4).