This randomized, multi-center trial aims to evaluate the advantages of underwater cold endoscopic mucosal resection technique (CS-EMR) in comparison to the conventional endoscopic mucosal resection technique (EMR) for laterally spreading colorectal lesions exceeding 20 mm in size. More precisely, our hypothesis posits that underwater cold EMR is non-inferior to conventional EMR in terms of recurrence rates, resection completeness and safety.

Endoscopic mucosal resection stands as one of the most commonly employed techniques for the removal of gastrointestinal lesions, particularly within the colon. "Piece-meal" endoscopic mucosal resection is the preferred approach for large colonic polyps without signs of deep infiltration. This method consists of the removal of lesions in multiple fragments.

The conventional procedure starts with the initial submucosal infiltration of the submucosal layer using a physiological solution and methylene blue, forming a cushion that facilitates tissue transection with the assistance of a diathermic snare. The goal is to remove the lesions in larger fragments whenever possible.

In contrast, the "cold" procedure, employs a specialized snare that enables tissue transection without the need for electrical current. This approach yields the same outcome as the conventional procedure but offers the advantage of reducing the risks associated with the use of diathermic current. Subsequently, the lesion fragments are retrieved for histological examination.

Inclusion criteria:

• all patients ≥ 18 years of age undergoing colonoscopy for any indication (screening, anaemia, surveillance)
• patients who were able to give informed written consent.

Exclusion criteria:

• lesions suspicious for submucosal invasion (e.g. Kudo V or Paris 0-IIa-IIc with nongranular surface).
• lesions with large (>10 mm) Paris 0-Is component that could compromise the nodular en-bloc resection and increase risk of submucosal invasion.
• suspected sessile serrated adenomas (SSAs) according to traditional features such as adherent surface mucus, cloud-like surface, interruption of mucosal vessels, Kudo II-o pit pattern.
• pedunculated polyps
• active/quiescent colitis
• patients with other lesions resected by hot snare during the same procedure.
• rectal lesions
• residual or recurrent adenoma after endoscopic mucosal resection