Inclusion Criteria:

- Diagnosis of ulcerative colitis, crohn's colitis or indeterminate colitis

- Disease duration ≥ 8 years

- Inflammation of at least 30% of colonic mucosa at some point between IBD diagnosis
and inclusion

- Age 18 - 70 years

- Signed informed consent

Exclusion Criteria:

- High grade dysplasia or colorectal cancer before inclusion

- subtotal or total colectomy before inclusion

- Clotting disorder or use of anticoagulants that can not be temporarily discontinued

- Serious comorbidities which prevent performing a colonoscopy

- Limited life expectancy

- Clinical or endoscopical disease activity (at the discretion of the treating
physician)