This is a retrospective observational cohort study. All interventions described are part of routine clinical care for acute severe ulcerative colitis (ASUC). Treatment decisions were made by treating clinicians per standard of care; the investigator did not prospectively assign, modify, or control any therapeutic interventions. Participants did not receive any intervention specifically for the purpose of this study. The study only involves retrospective analysis of existing medical records to compare real-world outcomes between different treatment exposure patterns.
