Measuring Endoscopic ACTIvity in Patients Treated With VEDOlizumab for Ulcerative Colitis

Inclusion Criteria: * age over 18 years, * established diagnosis of ulcerative colitis for at least 3 months * moderate to severe active ulcerative colitis with a Mayo endoscopic sub-score ≥ 1 before vedolizumab introduction * patients receiving vedolizumab according to French drug labelling (previous exposure to anti-TNF, contraindicated or intolerant to anti-TNF), * possibility of concomitant therapy including corticosteroids and immunosuppressors, * patients naive to anti-integrin, * no contraindication to proctosigmoidoscopy Exclusion Criteria: * age under 18 years * ulcerative colitis not proven, Crohn's disease, or inderterminate colitis * personal history of high-grade dysplasia or colorectal cancer * surgery with ileo-anal anastomosis * patients' refusal to participate in the study