The purpose of this study is to assess whether the use of large screen during colonoscopy will increase adenoma detection rate.

Colorectal cancer is the 3rd most common cancer in the world. Recently in Hong Kong it has surpassed lung cancer to be the most common cancer. Hence it is essential not only to have up-to-date surgical and oncological treatment but also a need an effective preventative strategy.

In the past few decades, removal of pre-malignant colonic lesions such as adenomas have been shown to prevent development of colorectal cancers. Colonoscopy is currently the only technique which can perform both detection and treatment during the same procedure. However, 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. Most ICs are suspected to arise from missed colon lesions during colonoscopy. Factors concerning missed colonic lesions are multifactorial such as adequate bowel preparation, skill level of endoscopists, the number of endoscopy staff in the room as "eyes" to help with polyp detection and withdrawal time.

Following a pilot study in our endoscopy unit, we believe the size of the screen projecting the endoscopic image may have a positive influence on adenoma detection. Therefore, we feel that a well-designed and adequately powered randomised controlled trial may help to confirm this.

Inclusion Criteria:

• Patients aged 18 years or above
• Referred to the endoscopy unit for diagnostic or surveillance colonoscopy

Exclusion Criteria:

• Familial history of Familial adenomatous polyposis or Hereditary non-polyposis colorectal cancer
• Known history of inflammatory bowel disease
• Emergency endoscopy of any nature (such as for gastrointestinal bleeding, assessment of large bowel investigation and colonic decompression)
• Patients with colostomy
• Previously incomplete colonoscopy (not including insufficient preparation)
• Patients with known palliative colorectal malignant disease Patients with coagulopathies Inability to give informed consent