Radiological primary sclerosing cholangitis in incident inflammatory bowel disease- a prospective Copenhagen IBD Inception Cohort study.

BACKGROUND & AIMS: Primary sclerosing cholangitis (PSC) is a chronic liver disease associated with long-term ulcerative colitis (UC) and Crohn's disease (CD). We aimed to determine its prevalence, clinical features, and impact in newly-diagnosed UC and CD. METHODS: In a prospective population-based inception cohort, all adult patients with newly-diagnosed UC or CD in a defined region of Denmark (2021-2023), were offered magnetic resonance cholangiopancreatography (MRCP). Primary outcome was the prevalence of radiological PSC. Patients were followed-up prospectively for a median of 2.0 years (IQR: 1.6-2.0, range 1.0-2.0). RESULTS: Of 527 patients, 389 patients (73.8%) (UC: 242; CD: 147) underwent MRCP, of whom 31 (8.0%) were diagnosed with radiological PSC (UC: 16 [6.6%]; CD: 15 [10.2%]), while seven (1.8%; UC: 5 [2.1%] and CD: 2 [1.4%]) had non-diagnostic PSC-like lesions, yielding a combined prevalence of 9.8%. Only 51.6% (16/31) presented with abnormal liver biochemistry. PSC prevalence was higher in patients with extensive colitis (9/73 [12.3%] vs. 7/164 [4.3%], p=0.02), but did not differ by age or sex, and was associated with higher rates of IBD-related hospitalization (41.9% vs. 23.4%, p=0.03) and biological therapies (38.7% vs. 21.4%, p=0.03) during follow-up. CONCLUSION: Radiological PSC or PSC-like lesions were present in 1 in 10 patients with incident IBD, often without biochemical abnormalities. These findings suggest a higher burden of radiological PSC at IBD onset than previously anticipated, although their long-term clinical significance remains uncertain. While MRCP at IBD diagnosis may prove clinically beneficial, confirmation from long-term follow-up and cost-effectiveness analyses is required before it can be recommended for screening.