This ASG video tip is brought to you by an educational grant from Braintree, a part of Cebella Pharmaceuticals, makers of SUTAB. Endoscopic intermuscular dissection with intermuscular tunneling for local resection of rectal cancer with deep submucosal invasion. The introduction of population-based screening has resulted in an increased incidence of early invasive rectal cancer. In recent years, primary treatment for these tumors has been shifting from major surgery towards local organ-preserving resection techniques. Recent studies suggest that it's also important to maximize the chance of achieving complete a zero resection for rectal cancers with deep submucosal invasion. In this report, we present a video of the removal of such a tumor using endoscopic intermuscular dissection with intermuscular tunneling. Endoscopic intermuscular dissection, or EID, is a resection technique which involves dissection in the intermuscular plane that is the space between the inner circular and outer longitudinal muscle layer. The technique was first described in 2017 by Rani and others. A recent preliminary study suggested that EID has favorable safety and feasibility outcomes. EID is mainly useful for resecting rectal cancers with suspected deep submucosal invasion. For these tumors, it has become clear that maximizing the chance of achieving complete a zero resection is also important. This is because SM2 and 3 lesions, without other high-risk factors, are associated with a negligible risk of lymph node metastasis that is less than 2%. In other words, complete local resection of deeply invasive tumors by EID could be curative in some cases. There are no special requirements for performing EID. The equipment and preparation are completely similar to conventional endoscopic submucosal dissection. This also makes the EID technique preferred over local surgical resection techniques, which often require more expensive equipment and general anesthesia. In this case report, a 70-year-old man underwent a screening colonoscopy after a positive fecal occult blood test. Colonoscopy revealed a rectal tumor with a diameter of 25 mm located 2 cm above the dentate line. Virtual chromoendoscopy of the depressed area showed a Q-5N pit pattern. MRI staging showed a CT12N0M0 rectal lesion in the anterior wall of the rectum, 3 cm above the anal verge. After obtaining informed consent from the patient, it was decided to perform an EID under proper falcidation. We will now demonstrate the EID procedure. First we marked the parameter of the lesion and injected a mixture of hydroxyethyl starch, inococarmine and adrenaline. Then a short mucosal incision was made at the oral side, followed by creating a mucosal incision at the anal side. Submucosal dissection was then started at the anal incision. Shortly thereafter, the inner circular muscle layer was reached and carefully incised to enter the intermuscular space. We then started intermuscular tunneling, that is dissection between the inner circular and outer longitudinal muscle layer. To facilitate safe intermuscular dissection, optimal counter-traction was obtained using gravity and the transparent hood. Proper identification of the different layers is also essential for safely performing EID. The goal of intermuscular tunneling is to create a tunnel from the anal to the oral incision. When the oral incision was almost reached, we identified the submucosal space and continued the dissection in this plane. After completing the intermuscular tunnel, the lateral margin was incised. Dissection was then continued from the lateral incision. After lateral dissection, the lateral edge of the muscle layer was mobilized. The other lateral edge of the lesion was mobilized in a similar manner. Lastly, the resection was completed and the specimen was retrieved for histological evaluation. After the resection, we carefully inspected the resection site to identify possible perforations. The resection site was left open and the patient was discharged the same day with oral antibiotics for 5 days. Histological evaluation showed a PT1-SM3 adenocarcinoma with negative lateral and vertical resection margins. In conclusion, we provided a step-by-step video explanation of EID with intermuscular tunneling. The EID technique may be particularly useful for local treatment of rectal cancers with deep submucosal invasion, as it enables complete R0 resection of these tumors with minimal interference with the TME plane. www.ottobock.com

endoscopic intermuscular dissection

intermuscular tunneling

rectal cancer

deep submucosal invasion

surgical resection