Background:The optimal technique for removal of diminutive or small colorectal polyps is debatable.

Objective:To compare the complete resection rates of cold snare polypectomy (CSP) and hot snare polypectomy (HSP) for the removal of adenomatous polyps(3-9mm).

Design：Prospective randomized controlled study. Setting：Three tertiary referral hospitals. Patients：we will recruit a total of 330 polyps(3-9mm). Interventions:Enrolled patients were randomly assigned to one of the two polypectomy protocols (CSP vs. HSP) using a computer-generated random sequence. If a patient had one or more polyps, all eligible polyps were removed using the initially assigned polypectomy protocol. After the initial polypectomy, additional EMR was performed at the polypectomy site to assess the presence of residual polyp tissue.

Main Outcome Measurements:The primary study outcome was to compare the complete polyp resection rate between groups. Secondary outcomes included rate of postpolypectomy adverse events, including bleeding, perforations,infection and rate of tissue retrieval(Complete resection was defined as the absence of residual polyp tissue in the EMR sections of the polypectomy site).

1、study objective and Contents

Study objective:

Compare cold snare polypectomy with cold forceps polypectomy with respect to their efficacy and safety for endoscopic resection of small colorectal polyps: a randomized controlled trial.

Study content:

1. Main Outcome Measurements: The primary study outcome was to compare the complete polyp resection rate between groups. Secondary outcomes included rate of postpolypectomy adverse events, including bleeding, perforations,infection and rate of tissue retrieval(Complete resection was defined as the absence of residual polyp tissue in the EMR sections of the polypectomy site).
2. Collect the pre-operation and post-operation data of patients who underwent a colonoscopy in the digestive disease center of Wulumuqi General Hospital of Lanzhou Militery Cammand from December 2015. to December 2016.Collect patients clinical data,Laboratory examination data, baseline data.

2、Key technical indicators and Solutions

1. key technique: After each polypectomy, additional EMR was performed at the polypectomy site, including an additional 1 to 2 mm clear margin, was resected by the snare,to evaluate for the presence of residual polyp tissue.
2. the implementation of colorectal polypectomy: the polypectomy will be performed by experienced clinician, our Department of Gastroenterology and Hepatology has conducted nearly thousand colorectal polypectomy,and is a national leader in this technology. All the operation done by our team, all the members of our team has been trained to operate according to the operation standardization.All points mentioned above can ensure the smooth implementation of the operation.

3、Research methods and technical routes to be used

1. The study was a multicenter, prospective,single-blind, randomized controlled study involving patients who underwent a colonoscopy from February 2016 to December 2016. It was conducted according to the Declaration of Helsinki Principles and was approved by the institutional review board of our hospital (2016LL001). The study was reported according to the CONSORT guidelines and was registered at www.clinicaltrials.gov. Written informed consent for this study was obtained from all patients.
2. Patients: Patients come to the digestive disease center of Wulumuqi General Hospital between 2016.02-2016.12 Inclusion criteria：

(1)patients aged >18 years who undergo a screening, surveillance, or diagnostic colonoscopy and are subsequently found to have colorectal polyps measuring 3-9 mm in size.(2) Patients who signed an informed consent.

Exclusion criteria:(1)patients taking antiplatelet or anticoagulant therapy during the past 1 week of the procedure;(2) known coagulopathy;(3) history of inflammatory bowel diseases;(4)polyposis syndrom;(5)Type IV shantian colorectal polyps;(6)American Society of Anesthesiology class III or more;(7) pregnancy;(8)Unable to provide informed consent.

(3)Random method: Enrolled patients were randomly assigned to one of the two polypectomy protocols (CSP vs. HSP) using a computer-generated random sequence. If a patient had one or more polyps, all eligible polyp swere removed using the initially assigned polypectomy protocol. (4)data collection:Laboratory data and previous colonoscopy data.Preoperative baseline data included:Patient entry sequence number,Operation method（CSP or HSP）,age,gender, take anticoagulant drugs or not(Warfarin , aspirin, clopidogrel), cause of desease, operation indications(Screening, inspection, polypectomy, fecal occult blood test positive, perianal rectal bleeding, other); Correlation check: 1.Blood routine, urine routine, stool routine + Occult Blood; 2,Liver and kidney function, electrolyte, blood sugar, blood coagulation, blood type, Rh factor, infection disease screening (hepatitis B, hepatitis C, HIV, syphilis and other); 3.Digestive tract tumor marker screening (CA19-9, CA24-2, CEA, etc.); 4.Abdominal ultrasound, electrocardiogram, chest X-ray. The postoperative data were: Bowel preparation (using the Boston Bowel Preparation Scale),Whether to insert the coloscope to the cecum, time of insertion,Whether to send the coloscope to the terminal ileum,Time from the insertion of the coloscope to thececum to Exit the colonoscope. Total time from the insertion of the colon to the exit of the colonoscopy.The number of polyps (per patient), polyp size (mm), anatomical (cecum, ascending colon, transverse colon, hepatic flexure, splenic flexure, descending colon, sigmoid colon, rectum), shape (flat, sessile,pedunculated ) , the number of polyps resected, Whether the naked eye view (NBI) is completely removed, the total operation time,whether the polyps were retrieved, postoperative hemorrhage (postoperative bleeding, hematochezia, delayed bleeding), Whether or not perforate, whether the use of hemostatic clip ( number), pathological diagnosis (tubulovillous adenoma, sessile serrated adenoma, hyperplastic polyp and other non neoplastic polyps), whether the additional EMR success after polypectomy, EMR operation time, the pathological results of EMR tissues (normal intestinal mucosa,tubulovillous adenoma, sessile serrated adenoma, Hyperplastic polyps, other non neoplastic polyps), whether the histological complete resection.

(5) Operation procedure：①Bowel preparation consisted of patients drinking a total of 4 L of polyethylene glycol solution before their procedures.Until the discharge of clean liquid (colorless or yellow transparent water samples). ②Total colonoscopies were prospectively performed by using a high-definition endoscope (CF-H260AL; Olympus Co, Tokyo, Japan) by 7 highly experienced endoscopists. All polyps found during colonoscopy were photographed, and their characteristics, including size,shape and anatomic location, were documented. The size of the polyp was assessed with the width of the biopsy forceps before the polyps were removed. ③Polyps that were deemed neoplastic (vessels surrounding oval, tubular, or branched pits under observation by high-definition white-light endoscopy and narrow-band imaging endoscopy) were subjected to polypectomy. Polyp size was defined by using the opening width of the biopsy forceps. If the size of the polyp was eligible for the study (3-9mm), polypectomy was performed by one of two randomized methods.④ Two kinds of operation methods are adopted: 1.CSP was performed by using a disposable oval snare with a diameter of 10 mm (SD-210U-10; Olympus) under gentle suction to reduce colon wall tension. The tip of the endoscope was deflected toward the polyp base to ensnare 1 to 2 mm of normal mucosa surrounding the polyp.2.HSP, which is using electrocoagulation on the basis of using cold snare.⑤After the polyps were removed, the ulcers were washed with saline lavage fluid. After that, another independent endoscopic surgeon judged whether the endoscopic eradication was successful. ⑥Afterward, additional EMR was performed at the polypectomy site to evaluate for the presence of residual polyp tissue.For histologic assessment of residual polyp tissues, the polypectomy site, including an additional 1 to 2 mm clear margin, was resected by the snare and Endocut current (VIO300D; Erbe Elektromedizin GmbH, Tubingen, Germany) after submucosal injection of a mixed solution (normal saline solution + 0.01% epinephrine). In the event that no tissue could be removed (e.g., if the original resection achieved a wide resection), or if EMR failed to get in situ mucosal specimens. At least four cold biopsies using forceps on the remaining margins were obtained. The primary polyp specimen and the specimen from the base of the polyp were placed in separate jars.⑦After each procedure, the polypectomy site was observed for 30 seconds to confirm the absence of immediate bleeding, the specimens were retrieved and stored in formalin.⑧The retrieved specimen was fixed on a plate by using pins. After indigo carmine solution was applied, the specimen was studied under a stereomicroscope with 8-power magnification to assess the presence of residual tissue by the endoscopist who performed the polypectomy. The presence of residual tissue was documented, and the plate was marked with a pen to indicate the most probable site of residual tissue. Cross-sections of the EMR specimens were collected at 1-mm intervals; accurate tissue section of the marked site was ensured. ⑨All tissue samples were cross-reviewed by 2 experienced pathologists who were blinded to the clinical information. Histological identification was carried out and the comprehensive analysis was carried out. The process is shown in Figure 1. ⑩The patients returned 1 week after each polypectomy to be informed of their pathology results and to be assessed for postprocedural adverse events, such as delayed bleeding. Complete resection was defined as the absence of residual polyp tissue in the EMR sections of the polypectomy site.

(6)Statistical analysis: card square test and Fisher exact test were used to compare categorical variables, the p value less than 0.05 was considered statistically significant, between groups of continuous variables and discrete variables were compared with a two sample t test, or Z test. All the data analysis by SPSS windows system.

(7)sample size estimation: according to Hyun-Soo Kim et al: a randomized controlled study of an GASTROINTESTINAL ENDOSCOPY: cold snare versus hot snare polypectomy for the complete resection of 5-9 mm sized colorectal polyps; a randomized controlled trial, according to the CSP with HSP complete resection rate was (79.1% vs 92.2%), the alpha value of the significant level of 0.05, grasp the degree 1 beta 0.9, according to pass (11.0) software calculated sample size for 300 cases. Taking into account the possible 10% of the rate of loss of access, sample size of 330 cases.

Cold snare polypectomy (CSP) has been shown to be safe and effective for the removal of polyps ≤10 mm in size， and is regarded as the ideal procedure for removal of small polyps. Hot snare techniques for diminutive polypectomy are still popular, but their use has decreased steadily in practice because of limited effectiveness and several drawbacks associated with the use of electrocautery,such as inadequate histologic interpretation and significant risk of complications. However, there have been few randomized controlled trials demonstrating complete resection rate by CSP or HSP for diminutive and small polyps. There are a paucity of data regarding which polypectomy technique is recommended according to polyp size and shape. The polypectomy techniques in the removal of small colorectal polyps in the 3-9 mm size range are not consistent. The study aimed at the direct comparison of the histologic polyp eradication rate of cold snare polypectomy (CSP) with that of hot snare polypectomy (HSP) in 3-9 mm sized flat or sessile colorectal polyps and the efficacy and safety of CSP to HSP in the removal of polyps 3-9 mm in size. In order to guide clinical practice.

Inclusion Criteria:

• patients aged ≥20 years who undergo a screening, surveillance, or diagnostic colonoscopy and are subsequently found to have colorectal polyps measuring 3-9 mm in size
• Patients who signed an informed consent

Exclusion Criteria:

• patients taking antiplatelet or anticoagulant therapy during the past 1 week of the procedure
• known coagulopathy
• history of inflammatory bowel diseases
• polyposis syndrom
• Type IV shantian colorectal polyps
• American Society of Anesthesiology class III or more
• pregnancy
• Unable to provide informed consent.

there is a plan to make individual participant data (IPD) available.