Colitis is inflammation of the large bowel and it is often caused by conditions known as ulcerative colitis and Crohn's disease. In these conditions, the body has an exaggerated inflammatory response against the bowel - the body attacks the bowel. Patients who have had colitis affecting most of the large bowel for more than 8 years are at increased risk of cancer of the large bowel. In view of this, many national gastroenterology organisations have recommended that such patients have regular colonoscopies to detect pre-cancerous areas and even early cancer in the large bowel. Early detection of such areas, will lead to early treatment thereby reducing the risk of developing significant large bowel cancer. These regular colonoscopies are known as surveillance colonoscopies.

Official international guidelines for surveillance in patients with ulcerative and Crohn's colitis advise to take 4 random samples of large bowel tissue (biopsies) every 10 centimeters and of any suspicious areas. Recent studies have shown that spraying dye such as indigo carmine (a type of food dye) helps highlight abnormal areas that could harbor pre-cancerous cells. This technique is time-consuming, and tedious. There are no set standards of what is considered a satisfactorily completed dye spray colonoscopy. The uptake of this technique in the UK has not been uniform. Therefore virtual chromoendoscopy has been studied as an alternative method to improve the detection of pre-cancerous tissue in patients with longstanding colitis.

Virtual chromoendoscopy systems enhances specific characteristics of the lining of the large bowel such as surface patterns and mucosal vasculature. This theoretically increases the detection of pre-cancerous tissue compared to high definition white light endoscopy alone. Narrow-band imaging or NBI (Olympus, Tokyo, Japan), Blue Laser (Fujinon, Tokyo, Japan) and OE scan (Pentax, Tokyo, Japan) use optical light filters to select particular narrow spectrums of red, green and blue light with a relative decrease in the proportion of red light. The Fujinon Intelligent Chromo-Endoscopy (FICE) system uses post hoc computer algorithms, applying different filters to the stored endoscopic images and enabling a theoretically endless number of combinations of filters that can be used. The Pentax I-SCAN system also allows post hoc modification of the images. It provides the ability to enhance the mucosal surface to better highlight mucosal changes.

These new imaging techniques have a theoretical advantage, which is extendedly used for sales purposes but so far has not been proven in the surveillance for precancerous or early cancer of the large bowel in patients with longstanding colitis.

Inclusion Criteria:

• Ulcerative Colitis or Crohn's colitis with a disease duration of >8 years for pancolitis or >15 years duration for left-sided colitis
• Aged 18 years and above
• Patients able to give informed consent

Exclusion Criteria:

• Persistent coagulopathy or platelet count <50x1012 which may preclude mucosal biopsy
• Known colonic IN or CRC
• Fulminant colitis
• Patients who have been previously randomised and withdrawn on 2 occasions due to poor bowel preparation
• Patients who are pregnant