RESUMEN
BACKGROUND: The introduction of biologic therapies and the 'treat-to-target' treatment strategy may have changed the disease course of ulcerative colitis (UC). AIMS: To describe the early disease course and disease outcome at 1-year follow-up in a population-based inception cohort of adult patients with newly diagnosed UC. METHODS: The Inflammatory Bowel Disease in South-Eastern Norway (IBSEN) III study is a population-based inception cohort study with prospective follow-up. Patients newly diagnosed with inflammatory bowel disease during 2017-2019 were included. Patients ≥18 years at diagnosis of UC who attended the 1-year follow-up were investigated. We registered clinical, endoscopic and demographic data at diagnosis and 1-year follow-up. RESULTS: We included 877 patients with UC (median age 36 years (range: 18-84), 45.8% female). At diagnosis, 39.2% presented with proctitis, 24.7% left-sided colitis and 36.0% extensive colitis. At the 1-year follow-up, 13.9% experienced disease progression, and 14.5% had received one or more biologic therapies. The colectomy rate was 0.9%. Steroid-free clinical remission was observed in 76.6%, and steroid-free endoscopic remission in 68.7%. Anaemia and initiation of systemic steroid treatment at diagnosis were associated with biologic therapy within the first year after diagnosis. CONCLUSION: In this population-based inception cohort, colectomy rate in the first year after diagnosis was low, and a high proportion of patients were in remission at 1-year follow-up. The use of biologic therapy increases, consistent with findings from previous studies.