[KASID Guidelines for the Medical Treatment of Ulcerative Colitis: 2026]

Ulcerative colitis (UC) is a chronic immune-mediated inflammatory bowel disease with an expanding therapeutic landscape and increasing clinical complexity. This guideline was developed by the Korean Association for the Study of Intestinal Diseases (KASID) to provide updated, evidence-based recommendations for the medical management of adult patients with UC in Korea. Guideline development used the GRADE-ADOLOPMENT approach, with source guidelines appraised using AGREE II. Key questions were formulated using the PICO framework, source guidelines and consensus documents published from 2017 through 2025 were appraised, and targeted literature searches covering January 2020 through April 2026 were conducted in PubMed, Embase, the Cochrane Library, and KoreaMed. The guideline addresses induction and maintenance therapy for mild-to-moderate and moderate-to-severe UC, management of acute severe UC, indications for surgery, use of biosimilars and subcutaneous formulations, and treatment optimization and sequencing. Recommendations were formulated based on structured evidence review and Evidence-to-Decision considerations, and were finalized through a modified Delphi consensus process and external review. The final recommendations emphasize objective disease control, individualized treatment selection, timely escalation or surgery in acute severe UC, and shared decision-making based on efficacy, safety, comorbidities, prior treatment exposure, patient preference, drug accessibility, and the Korean healthcare context. This guideline is intended to support consistent, practical, and patient-centered care and to improve long-term outcomes for adults with UC.