<qa>  What is the endoscopic score of Mayo Clinic?Male or female, 18 years of age or older. Ulcerative Colitis described according usual criteria, diagnosed for at least 1 year. Oral maintenance treatment with 5-aminosalicylic acid 5-ASA only for at least 3 months with a dosage of 2 to 3 gday. Clinical remission for at least 3 months Mayo Clinic score and endoscopic remission endoscopic score of Mayo Clinic at the inclusion. Signed informed consent form. 