This Randomized, Single-center Trial Aims to Evaluate the Advantages of Underwater ESD (U-ESD) in Comparison to the Conventional ESD (C-ESD).

Large nonpedunculated colorectal lesions are increasingly detected thanks to screening programs worldwide. ESD is the technique which provides a high-quality resection of these large polyps. Nevertheless, colorectal ESD is burdened by technical difficulties and several adverse events affecting its outcomes. The adverse events could be life-threatening, call for or prolong the hospitalization, require blood transfusion, additional endoscopic or surgical procedures and increase costs. Failure of endoscopic resection requiring surgery for benign lesions could affect patients' quality of life and increase healthcare systems' costs. Thus, improving colorectal ESD outcomes is an important clinical and medico-economic objective. The underwater setting with saline has been already established as a better option than conventional CO2 insufflation for EMR of large colonic polyps. Moreover, use of the underwater approach for colorectal ESD has been increasingly reported with good results in the last few years. However, a randomized comparative trial between conventional and underwater colorectal ESD clarifying which should be the preferred approach is lacking. Expected benefits are a decrease of adverse events and an increase of successful R0 resection rate of colorectal ESD.