The investigators plan to conduct a multi-center, randomized controlled trial to investigate the efficacy of cap-assisted chromoendoscopy as a screening test for detection of colorectal polyp. This study will be performed using web-based research network, e-VELOS in Korea.

Various endoscopic tools have been tried to reduce polyp missing rate which has been reported to be 20-25%. Transparent cap-assisted colonoscopy has been suggested to improve visualization of the lesion that are difficult to access, such as tangentially located lesions and those located within a limited luminal space. Chromoendoscopy with indigocarmine spraying was reported to increases the detection rates of polyp, especially in right colon and rectum. However, there also have been mixed results regarding polyp detection rates of the endoscopic methods. Moreover, there is no data regarding the impact of the screening tools on longterm recurrence rate of colorectal polyp. Therefore, in this study, we intend to perform a multi-center, randomized controlled trial to investigate the efficacy of cap-assisted chromoendoscopy as a screening test for detection of colorectal polyps. This study will be performed using web-based research network, e-VELOS in Korea.

Inclusion Criteria:

• All asymptomatic colonoscopic examinees

Exclusion Criteria:

• Familial history of hereditary colorectal cancer
• History of colorectal cancer
• Patients had received colonoscopy examination before
• Familial or past history of FAP(familiar adenomatous polyposis)
• Colonic polyposis syndrome
• Prior colonic resection of any part of the colon
• Allergy to indigo carmine
• Inflammatory bowel disease
• Pregnancy
• Inability to provide informed consent