In 2015, there were approximately 1.7 million new cases of colorectal cancer（CRC）, and the deaths was close to 832,000. CRC has become the third most common malignant tumor in the world and the second leading cause of cancer death. This is mainly because adenomatous polyps can be transformed into cancer through adenoma-cancer sequences. Screening for CRC has been shown to prevent CRC and related deaths, especially colonoscopy and endoscopic resection of adenomatous polyps.

Currently, the main methods of resection for polyps below 20 mm include hot snare polypectomy (HSP) and cold snare polypectomy (CSP). Due to the use of electrocautery, HSP has been shown to cause damage to the deep submucosa, the muscularis propria and submucosal arteries, resulting in postoperative bleeding, perforation and other adverse events. Compared with HSP, the mechanical cutting method is called CSP without electrocautery. Due to the short operation time and low incidence of adverse events, especially after polypectomy, it has caused more and more attention of endoscopists. The removal of 5 mm polyps from CSP has been recommended as the preferred technique by the European Society of Gastrointestinal Endoscopy(ESGE) Guidelines. A recent multicenter, prospective study in Japan recommended CSP as the standard treatment for excision of 4-9mm polyps. However, the average diameter of polyps in this study was 5.4 mm, which was not sufficient for the safety of CSP in polyps above 5 mm. In addition, there are few prospective studies of CSP complete removal of colorectal polyps 10-15 mm. More importantly, the report pointed out that 10% of 5 to 20 mm polyps were not completely removed, and some studies have shown that the cut polyp specimens are not sufficient for adequate pathological evaluation, which the researchers do not fully recognize.

In this study, the investigators were interested in comparing the complete resection rates of large (10 -15 mm) and small (4-9 mm) colorectal polyps with CSP and HSP and improved methods for evaluating complete resection.

Participants who meet inclusion criteria will be asked to participate, investigators will include all patients with resectable polyps, but only adenomatous polyps will be included for analysis. See also inclusion and exclusion criteria.

Colonoscopy, after bowel preparation with polyethylene glycol solution was performed using standard colonoscopes (GIF-HQ290I) and polypectomy snares.

All procedures were performed by experienced endoscopists(each with over 1000 colonoscopies performed) including CSP and HSP. All patients with a colorectal 5-15 mm polyp detected will be randomized to receive HSP and CSP treatment. Polyp size will be measured using the tip of the snare catheter (2.5mm). Difficulty of resection will be grade by polyp resection time. Following the resection, jet stream of water will be used to wash mucosal defect thoroughly. After endoscopist's attestation that polyp removal was complete by carefully observe the resection margins with near focus mode, for large lesions(10-15mm)4 biopsies will be performed from all four quadrants of resection margins, for small lesions(4-9mm) biopsies were performed from two marginal sites located symmetrically on the left and right of the mucosal defects to confirm residual polyp tissue. Difficulty of resection will be grade by polyp resection time. Following the resection, jet stream of water will be used to wash mucosal defect thoroughly. After endoscopist's attestation that polyp removal was complete by carefully observe the resection margins with near focus mode, for large lesions(10-15mm)4 biopsies will be performed from all four quadrants of resection margins, for small lesions(4-9mm) biopsies were performed from two marginal sites located symmetrically on the left and right of the mucosal defects to confirm residual polyp tissue.

If polyp resection is complicated by bleeding(not self-sustained), no biopsies will be taken and any additional polyps that will be found during the remaining examination will be excluded from analysis. Severe bleeding that will complicate resection margins examination will be excluded from analysis, Endoscopic haemostasis will be performed when active haemorrhage continued for ≥30s.

A single research subject may have many eligible polyps. To avoid taking many biopsies, the investigators will not include more than 5 eligible polyps(the first 5 that are detected) per patient in the study.

Inclusion Criteria:

• Patient ≥40 and <70 years old
• Provide written informed consent
• Patients are found to have colorectal polyps between 5 and 15mm in size

Exclusion Criteria:

• History of inflammatory bowel disease
• Polyposis of the alimentary tract
• Antiplatelet or anticoagulant therapy 5 days before the procedure
• Pregnancy
• Haemodialysis
• An American Society of Anaesthesiologists class III or higher
• Depressed lesions and lesions highly suspected to be cancerous based on endoscopic appearance.

RCT-HSP-CSP