Patients with colitis require regular 'surveillance' colonoscopy as their risk of developing colon cancer is at least 2.5 times that of the general population. However, cancer in colitis develops as flat lesions called dysplasia, that can be easily missed at routine colonoscopy. As a result NICE guidelines for colitis surveillance recommend the use of a technique called chromoendoscopy (CE) in which a water-soluble blue dye is sprayed through the colonoscope to coat and highlight the lining of the bowel, making dysplasia easier to see. Although CE is accepted as best practice for surveillance it is time-consuming, technically difficult and requires expertise to interpret the appearances. For these reasons, its use is not widespread and the vast majority of patients still receive the inferior 'routine' colonoscopy without CE.

New technology means that the video image obtained during colonoscopy can be digitally enhanced and coloured at the press of a button - termed virtual chromoendoscopy (VCE). This could make surveillance colonoscopy shorter, more comfortable and cleaner (resulting in a more 'dignified' experience) as well as cheaper and less technically difficult.

The main objectives to be explored in this feasibility study (and the larger trial) were informed by a PPI meeting, which placed the ability to detect dysplasia at equal importance with the participant's experience of the procedure in terms of speed, comfort and dignity.

This is primarily a feasibility study to assess patient experience, recruitment and retention rates to the investigators' specified trial design, to support the development of a larger crossover trial to compare VCE to CE during surveillance colonoscopy for colitis.

In the recruitment period, 60 patients will be approached when they are invited to attend for scheduled surveillance colonoscopy. Eligible patients (18-75 yrs) who agree to participate will be randomised to undergo CE or VCE as the first procedure. Data will be captured by an Observer using a bespoke Access-based program.

The site and number of any biopsy samples taken will be recorded alongside the Endoscopist's prediction, based on visual appearance, of whether they think the area biopsied is actually dysplasia.

After an agreed interval (no more than 8 weeks, usually 3-6), participants will undergo a second colonoscopy with the second technique, performed by an Endoscopist blinded to the results of the first test, and data captured as before. For each procedure, a questionnaire assessing immediate patient experience will be administered in the Endoscopy department, after the participant has recovered from the procedure. Participants will also be given a second questionnaire assessing their overall experience to take home and complete 48 hours after the procedure, which will be returned by post.

Inclusion Criteria:

Any patient eligible for colitis surveillance colonoscopy by British Society of Gastroenterology guidelines:

• Ulcerative pan-proctocolitis or Crohn's colitis of 8 or more years duration
• With or without co-diagnosis of primary sclerosing cholangitis

Exclusion Criteria:

• Inability to provide informed
• Written consent

Patient level data will not be shared. Cohort results will form publication/output