One investigator is out-of-service due to carrying out another task.

The primary aim of this study is

- to explore the usefulness of Endocuff Vision in colonoscopy on adenoma detection rate (ADR).

Other aims include to explore the data below when Endocuff Vision is used.

Mean adenomas detected per procedure, MAP Proximal Adenoma detection rate, pADR Polyp detection rate, PDR Proximal polyp detection rate, pPDR Mean polyps detected per procedure, MPP Withdrawal time, WT Cecal intubation rate, CIR Cecal intubation time, CIT

Colorectal cancer is common in China. Most colorectal cancers happen when an adenoma becomes cancerous. Doctors use colonoscopy to look inside the colon and rectum and find adenomas and remove them. Removing adenomas is known to reduce the chances of a person developing colorectal cancers. The ability of colonoscopists finding adenomas varies, and there is a lot of researches into how to improve "adenoma detection rates".

A new device, called the Endocuff Vision has been shown to improve the rate of polyp detection at colonoscopy, and to make polyp removal easier. Previous studies have shown that there is a significant improvement in detection of adenomas when an Endocuff Vision is used (with the rate of detection of adenomas rising from 49% to 66%). Colonoscopists who have used the Endocuff Vision before also feel that polyp removal is easier when it is on the colonoscope. This study will randomise patients coming for colonoscopy to have their procedure performed as usual or as an Endocuff Vision-assisted colonoscopy. The investigators will record polyp and adenoma detection rates, duration of procedure, participant comfort levels, and complications. All patients referred for colonoscopy will be invited in 5 centres, recruiting a total of 1200 participants.

Inclusion Criteria:

• All patients referred for screening, surveillance, or diagnostic colonoscopy
• All patients must be able to give informed consent

Exclusion Criteria:

• Patients with any absolute contraindications to colonoscopy
• Patients with established or suspicion of large bowel obstruction or pseudo-obstruction
• Patients with known colon cancer or polyposis syndromes
• Patients with known colonic strictures
• Patients with known severe diverticular segments (that is likely to impede colonoscope passage)
• Patients with active colitis (ulcerative colitis, Crohn's colitis, diverticulitis, infective colitis)
• Patients lacking capacity to give informed consent
• Pregnancy
• Patients who are on clopidogrel, warfarin, or other new generation anticoagulants who have not stopped this for the procedure.
• Patients who are attending for a therapeutic procedure or assessment of a known lesion