The aim of this international multicenter study is to compare the adenoma detection rate and adenoma miss rate of conventional and Endocuff Vision-assisted colonoscopy.

Rationale: Population screening programs for colorectal cancers (CRC) are increasingly adapted as a public health initiative with the primary goal to prevent CRC and CRC related deaths. [2-4] The ultimate benefit of CRC screening relies on the detection and resection of (pre-)malignant colon lesions, and for this colonoscopy is the preferred modality. Recently, concerns have been raised about the effectiveness of colonoscopy in the prevention of CRC after several studies reported unexpected high incidence rates of interval carcinomas (IC), especially in the proximal colon.[5-9] Most ICs are suspected to arise from missed colon lesions during colonoscopy. The retrograde approach of colonic inspections may contribute to colon lesions remaining undetected as it limits visualization of the proximal sides of haustral folds and flexures. Endocuff Vision® is a single-use, disposable medical device designed to improve the detection of colon lesions. The 'finger-like' projections of the device provide fold retraction allowing the visualization of otherwise hidden anatomical areas. Additionally, Endocuff Vision® may improve scope tip stability and prevent scope slippage.

Objectives:

1. To compare adenoma miss rates (AMR) between Endocuff Vision®-assisted colonoscopy (EAC) and conventional colonoscopy (CC)
2. To compare adenoma detection rates (ADR) between EAC and CC
3. To assess whether a proposed increased ADR and reduced AMR with EAC is indeed due to the fold-flattening device or merely a consequence of the second colonoscopy procedure performed.
4. To assess the clinical relevance of the polyps missed during the first colonoscopy procedure.

Study design: This multicenter, randomized, same-day, back-to-back tandem colonoscopy trial will include four separate study groups: group A; CC followed by CC, Group B; CC followed by EAC, Group C; EAC followed by CC, and group D; EAC followed by EAC.

Study population: Patients between the ages of 40 and 75-years referred for screening (non-IFOBT based), diagnostic or surveillance colonoscopy.

Main study parameters/endpoints: The primary endpoint of the study will be AMR.

Secondary endpoints include; ADR, mean number of adenomas detected per colonoscopy procedure, number of sessile serrated polyps, the total number of colon lesions found during the first and second examination (which will be compared for size, colon distribution, morphologic and histopathological characteristics), cecal intubation rates, bowel cleansing levels, procedure times, sedation use, (severe) adverse events, patient reported outcome (pain) and post-colonoscopy surveillance intervals applying European and United states surveillance guidelines.

Inclusion Criteria:

• Patients, aged between 40 and 75-years old, referred and scheduled for either screening (non-FIT/gFOBT based), diagnostic or surveillance colonoscopy.

Exclusion Criteria:

• Prior surgical resection of any portion of the colon or a history of radiotherapy for any abdominal or pelvic disease.
• Personal history of colon cancer or polyposis syndrome.
• Familial adenomatous polyposis (FAP)
• Known colitis or suspicion of colitis (ulcerative colitis, Crohn's colitis, diverticulitis, infective colitis).
• Lower gastro-intestinal bleeding requiring acute intervention.
• Suspicion of large bowel obstruction or toxic megacolon.
• Prior incomplete colonoscopy (not including insufficient preparation).
• Patients referred for a therapeutic procedure or assessment of a known non-resected lesion.
• Not sufficiently corrected anticoagulation disorders
• Poor general condition (>3 American Society of Anesthesiologist)
• Overweight (>120 kg)
• Inability to provide informed consent.

Participants will be blinded for the allocation. Physicians can not be blinded for the use of Endocuff, but during the first procedure they will be blinded for the second procedure method to limit observer related bias.