Introduction:Endoscopic submucosal dissection (ESD) allows the en bloc resection of colorectal epithelial tumors regardless of size. Although ESD is minimally invasive and yields favorable outcomes, it is technically difficult and requires a long procedure time. In addition, colorectal ESD is associated with a particularly high risk of complications, due to the thin bowel wall, bowel flexion, and peristalsis.Direct visualization of the submucosal layer by traction of the lesion after mucosal dissection would make ESD performance easier. S-O clips traction lesions toward the lumen, facilitating direct visualization of the submucosal layer, resulting in efficient dissection due to the traction effect and adequate dissection depth. Use of this traction device can contribute to shortening the procedure time and reducing the risk of complications. This multicenter randomized controlled trial will evaluate the usefulness of the S-O clip in colorectal ESD and assess the procedure time and frequency of complications associated with the procedure.Methods/design:This multicenter, randomized control trial will enroll 200 patients at 4 hospitals in Japan undergoing ESD for colorectal epithelial tumors. Patients who meet the inclusion and exclusion criteria will be randomized to undergo ESD using S-O clips or conventional ESD. Patients will be randomized by a computer-generated random sequence with stratification by operator experience (trainee or expert), tumor location (colon/rectum), and institution. The primary endpoint will be ESD procedure time, defined as the time from the start of the local injection into the submucosal layer to the end of dissection. Other outcomes will include the rates of procedural complications, en bloc resection and cure.Discussion:ESD using the S-O clip is expected to shorten procedure time, reduce the incidence of adverse events, and standardize the procedure. This study may resolve clinical questions about whether ESD using the S-O clip traction device is more effective and safer than conventional ESD.