Colorectal cancer is a maior cause of morbidity and mortality worldwide.Colonoscopy and removal of all adenomas is the most efficient method to prevent colorectal cancer.The most colorectal polyps detected are small(<10mm) and diminutive(≦5mm) during colonoscopy.At that size,the are overwhelmingly hyperplastic or adenomatous,and rarely harbour high-grade dysplasia,cancer or sessile serrated adenoma/polyp.Traditional white-light endoscopy cannot reliably distinguish between small adenomatous and hyperplastic polyps,thus,real-time recognition of the polyp histology during colonoscopy has the potential to minimize both the costs and complications associated with endoscopic biopsy and polpectomy.Linked color imaging(LCI),a new system for endoscopy modality,creates clear and bright endoscopic images by using short-wavelength narrow-band laser light combined with white laser light on the basis of magnifying blue laser imaging(BLI) technology. it is easier to recognize a slight difference in color of the mucosa. This is a study to investigate the impact of Linked color imaging endoscopes on the in vivo histology prediction of colonic polyps.

This is a prospective study comparing the accuracy of linked color imaging(LCI) and standard white light colonoscopes in the diagnosis of small and diminutive colorectal polyps.

Inclusion Criteria:

- 1.ability to provide written informed consent and undergoing colonoscopy. 2.The patient is undergoing colonoscopy for screening, for surveillance in follow-up of previous polypectomy or for diagnostic work-up.

3.detection and retrieval for histologic examination of at least one polyp< 10mm in size and/or 5mm in size

Exclusion Criteria:

• Patients were previous colon resection
• Patients were a diagnosis of inflammatory bowel disease,familial polyp syndromes or poor bowel preparation
• suspected chronic stricture potentially precluding complete colonoscopy
• Patients had polypectomy or had coagulopathy/thrombocytopenia
• Patients had diverticulitis or toxic megacolon;previous radiation therapy to the abdomen or pelvis;severe cardiovascular,pulmonary,liver,or renal disease;and coagulation disorders or use of anticoagulants.
• all of polyps could influence surface pattern or/and color assessment

Consecutive adult patients who were referred for elective outpatient colonoscopy will be asked to enroll into this trial if the candidate meets the study inclusion and exclusion criteria.