Cold or Hot Snare Endoscopic Mucosal Resection for 10-19mm Non-pedunculated Colorectal Polyps

Inclusion Criteria: * 18-80 years of age; * undergo colonoscopy in the Digestive Endoscopy Center of Peking Union Medical College Hospital, Beijing Tsinghua Changgung Hospital or Seventh Medical Center, General Hospital of the Chinese People's Liberation Army; * volunteer to participate in this study and sign informed consent; * at least one polyp sized 10-19 mm (Paris classification Is or IIa) by colonoscopy. Exclusion Criteria: * American Society of Anesthesiologists (ASA) status class 3 or above; * poor bowel preparation (Boston bowel preparation scale \< 6 points); * known or endoscopic features indicating the submucous infiltration or malignancy; * oral anti-coagulants, or antiplatelet agents, or known blood coagulation disorders, or bleeding tendency (platelets\<50000 cells/mm3 or INR\>1.5); * a history of colorectal resection; * emergency colonoscopy (hemodynamic instability and/or continued active gastrointestinal bleeding and/or requiring intensive care patients); * inflammatory bowel disease, familial polyposis, and colorectal cancer; * pregnancy or lactation; * severe cardiopulmonary dysfunction, liver cirrhosis, chronic kidney disease, other malignant tumors, or severe infectious diseases.