Cohort of Patients With Ulcerative Colitis or Polyps Followed in CHU de Bordeaux Associated With a Biocollection - COLIBRI

* Inclusion criteria: * General Inclusion Criteria: * Patients covered by a social security system. * French-speaking patients. * Patients aged ≥18 years. * Patients who have provided free, informed, and written consent (no later than the inclusion day and before any research-related examination). * Specific Inclusion Criteria for the UC Group: * Patients diagnosed with ulcerative colitis (UC) according to the European Crohn's and Colitis Organisation (ECCO) guidelines. * Patients undergoing lower gastrointestinal endoscopy or rectocolic surgery. * Non-UC Patients with Polyps Group: * Patients undergoing colonoscopy with resection of hyperplastic polyps in the rectum, sessile serrated lesions, or adenomas \>2 cm. * Exclusion criteria: * Patients with perianal, ileal lesions, or endoscopic features of colonic lesions suggestive of Crohn's disease. * Pregnant or breastfeeding women. * Patients under legal protection or unable to provide informed consent. * Patients deprived of liberty by judicial or administrative decision, hospitalized without consent, or admitted to a healthcare or social institution for reasons unrelated to the study.