This study compares different approaches to endoscopic mucosal resection (EMR) of large non-pedunculated colorectal polyps (≥20mm) in a 2 x 2 randomized design. The first randomization will assign half of patients to polyp resection with electrocautery ("hot" snare EMR) and half of patient to polyp resection without electrocautery ("cold" snare EMR). The second randomization will assign half of patients to polyp removal using Eleview as the submucosal injection agent, and the other half using placebo (normal saline with methylene blue) as the submucosal injection agent.

Electrocautery, or hot snare resection has long been considered the standard approach to polyp resection. A major limitation is a 5 to 10% risk of major adverse events. Recent studies suggest that snare resection without electrocautery - so-called cold snare EMR - may be safer than hot snare EMR. The concern with cold snare resection is a potentially lower efficacy, because cold snare resection requires the removal of a large polyp in smaller and greater number of pieces than with hot snare resection. This may lengthen procedure time and increase the risk of incomplete resection.

Furthermore, there is uncertainty about the optimal injection solution for lifting of the polyp prior to resection. Normal saline with methylene blue as the contrast agent is frequently used, but is limited by fast dissipation of the polyp lift. Eleview is a newly approved viscous solution (that contains methylene blue), which provides a longer polyp lift than normal saline. It is unclear how these two solutions compare with respect to resection efficacy and safety.

Inclusion Criteria:

• Any patient ≥18 who presents for a colonoscopy and who does not have criteria for exclusion
• Patients with a ≥20mm non-pedunculated colorectal polyp

Exclusion Criteria:

• Pedunculated polyps (as defined by Paris Classification type Ip)
• Suspected adenocarcinoma with deep submucosal invasion
• Patients with ulcerated depressed lesions (as defined by Paris Classification type III) or confirmed adenocarcinoma
• Patients with inflammatory bowel disease
• Patients who are receiving an emergency colonoscopy
• Poor general health (ASA class>3)
• Patients with coagulopathy with an elevated INR ≥1.5, or platelets <50
• Inadequate bowel preparation (Boston Bowel Prep Scale, total score ≤2)
• Pregnancy

Randomization 1 (Cold vs. hot snare group): Masking only of participants Randomization 2 (Eleview vs Placebo): Masking of all checked above