Colorectal cancer is the second most common cause of cancer death in the US. Colonoscopy is considered the best test colorectal cancer screening. It allows resection of adenomatous polyps (a known cancer precursor) and thus, interrupt the adenoma-carcinoma sequence. Despite the potential benefit of screening colonoscopy recent studies have reported cases of colorectal cancers in a short interval after prior screening or surveillance colonoscopies. One possible cause of such interval cancers may be incomplete resection of adenomatous polyps and hence ongoing growth and cancer development in such lesions. Complete resection may be particularly important for polyps of at least 5mm in size as up 10% of such polyps higher risk lesions as villous adenoma, tubulovillous adenoma, high grade dysplasia, or early carcinoma.

Although adenoma resection of sessile and flat adenomatous polyps between 5 and 20mm is believed to be well standardized data on complete resection of adenomatous tissue are sparse. This may be related to the assumption that using a snare with electro-cautery will successfully remove the polyp and cauterize remaining marginal adenomatous tissue and hence completely remove and or destroy the lesion.

The investigators are interested in examining how often sessile adenomatous polyps between 5 and 20mm are completely removed using standard polypectomy snare. The investigation was also directed at a comparison between complete resection of polyps between 5 and 9mm and 10 and 20mm.

All patients who present for a colonoscopy and meet inclusion and exclusion criteria will be asked to participate, and all patients with resectable polyps will be included. See also inclusion and exclusion criteria.

All patients will have undergone a regular bowel preparation with polyethylene glycol lavage with 4-6 L until clear rectal fluid is evacuated.

Polyp resection will be performed by experienced endoscopists (each with over 500 colonoscopies performed). All polyps between 5 and 20mm will be removed with an electro-cautery snare. Polyp size will be estimated using the snare catheter (2.5mm) or the snare diameter (10x20mm, 15x30mm, 20x20mm) before resection. The endoscopist will grade the difficulty of resection. Following the resection, the endoscopist will closely examine the resection margins. Biopsies will be taken from resection margins: 2 biopsies will be obtained from opposite margins for polyps 5-9mm, and 4 biopsies will be taken for polyps 10-20mm from all four quadrants of the resection margins. In case of assumed incomplete resection this will be documented and further (piecemeal) resections should be done, if this is not feasible, margins can be cauterized according to standard polypectomy resection (e.g. by argon beamer coagulation) after previous biopsy. Only those polyps that are found to be adenomatous polyps will be included in the analysis.

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. Any bleeding from the margins after polypectomy will be treated by endoscopic injection using diluted epinephrine (1:10.000).

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.

Laboratory Analysis:

Polyps and biopsies will be sent to the pathology lab of each center. The polyps will be evaluated according to common practice. In addition information regarding resection margins will be provided for each polyp: R0= free of adenomatous tissue, R1=adenomatous tissue detected in the margin. This information is not routinely provided by the pathologist as there is so far no data whether this information is reliable. Only adenomatous polyps will be included in the analysis. Hyperplastic polyps will not be included. Biopsies will only be processed after the diagnosis of an adenomatous polyp was made. Biopsies will be evaluated for presence of adenomatous tissue. The additional impact for the pathology lab includes a) processing of biopsies belonging to the polyp specimens, and b) providing information on polyp margins. The VA pathology lab estimated the financial impact to be low and there will be no financial requests. The pathological diagnosis, including the reading of the biopsies, will become part of the medical record. If biopsies contain adenomatous tissue the patient will be ask to return for a follow-up colonoscopy within 1 year. This is within current standard of care to repeat a colonoscopy to assure complete adenoma resection.

Inclusion Criteria:

• Any patient ≥40 and <85 who presents for a colonoscopy and does not meet any of the exclusion criteria mentioned below will be asked to participate
• All patients who are found to have colonic polyp between 5 and 20mm in size will be included in the study

Exclusion Criteria:

• Pedunculated polyps (estimated stalk diameter < 50% polyp head diameter, stalk at least 5 mm)
• Any suspicion of perforation or deeper defects after polypectomy, irrespective whether treated or not.
• Post-polypectomy bleeding requiring hemostasis.
• Patients with known inflammatory bowel disease or active colitis
• Patients who are receiving an emergency colonoscopy
• Poor general health (ASA class>3)
• Patients on coumadin or with coagulopathy with an elevated INR ≥1.8, or platelets <50.
• Poor bowel preparation
• Patients who do not consent
• Pregnancy

Participants eligible for recruitment are patients who present for a colonoscopy to the VAMC or DHMC Gastroenterology department conducting this study. Upon arrival for a scheduled colonoscopy patient records will be reviewed to determine eligibility.