People with inflammatory bowel disease (IBD), such as ulcerative colitis or Crohn's disease affecting the colon, have a higher risk of developing colon cancer over time. To catch early signs of cancer, regular colonoscopies are recommended. In this study, the investigators are comparing two advanced methods of examining the colon during these surveillance colonoscopies. One method uses a special dye sprayed inside the colon to highlight abnormal areas (called dye-based chromoendoscopy). The other method uses new technology built into the camera to enhance the view without needing any dye (called virtual chromoendoscopy). Both methods use modern, high-definition equipment.

The purpose of this study is to find out if the newer, dye-free method is as good as the traditional dye method at detecting pre-cancerous changes (called dysplasia) in people with IBD.

Adults with IBD who are due for a routine surveillance colonoscopy may be invited to take part. Participants will be randomly assigned to one of the two methods. No additional procedures are involved, and only the way the colon is viewed differs. The investigators will also look at how long the procedures take, how many biopsies are needed, any complications, and how patients experience the exam. Participants will be followed over time using national health records to check for long-term outcomes.

This research will help doctors better understand which method is most effective and comfortable for patients, and may guide future recommendations for cancer screening in people with IBD.

This is a multicenter, prospective, randomized, non-inferiority clinical trial designed to compare the diagnostic performance of two high-definition endoscopic imaging techniques used during surveillance colonoscopy in patients with longstanding inflammatory bowel disease (IBD) who are at increased risk for colorectal cancer. Participants will be randomly assigned to undergo colonoscopy using either a virtual (dye-free) chromoendoscopy method or a conventional dye-based chromoendoscopy technique. The primary objective is to evaluate whether virtual chromoendoscopy is non-inferior to dye- based chromoendoscopy in detecting dysplasia, a precancerous condition in the colon. Secondary outcomes include the number and type of lesions detected, predictive accuracy of targeted biopsies, examination times, patient-reported experience, complication rates, and biopsy frequency. Eligible participants are adults with a history of extensive colonic IBD of at least eight years, or additional high-risk factors such as primary sclerosing cholangitis or family history of colorectal cancer. Patients with previous colorectal cancer, prior colectomy, known untreated dysplasia, or contraindications to dye application will be excluded. All procedures will be performed using high-definition equipment and standardized bowel preparation protocols. The study includes long-term follow-up through national health registries to evaluate cancer outcomes and subsequent procedures at one and three years post-colonoscopy. The trial will be conducted across several academic and regional centers in Sweden, with an anticipated enrollment of approximately 480 patients to account for potential attrition. This study seeks to inform future guidelines by determining whether a less resource-intensive and potentially more patient-friendly method can provide equivalent surveillance efficacy in this high-risk population.

Inclusion Criteria:

• Age ≥ 18 years and one of the criteria beneath:
• Extensive ulcerative colitis or indeterminate colitis (IBD-U), or Crohn's colitis involving at least one-third of the colon, with a disease history of at least 8 years
• IBD or IBD-U with primary sclerosing cholangitis (PSC)
• IBD or IBD-U with a family history of colorectal cancer in a first-degree relative

Exclusion Criteria:

• History of colorectal cancer or prior colectomy
• Contraindications to dye use
• Colonoscopies for therapeutic purposes
• Pregnancy
• Inability to consent