Functional Strictures in PSC Evaluated by Hepatobiliary Contrast-Enhanced MRI

Overview

This study introduces the concept of potential functional strictures (PFS) in PSC patients, identified via impaired gadoxetic acid excretion on hepatobiliary phase MRI. The investigation compares PFS detection and localization with traditional dominant stricture (DS) and high-grade stricture (HGS) assessments on T2-MRCP, using ERCP as the reference standard.

Background

Primary sclerosing cholangitis (PSC) is a chronic liver disease characterized by fibroinflammatory strictures in the biliary tree, leading to progressive liver damage and complications such as portal hypertension and hepatic dysfunction. Dominant strictures (DS) are common and clinically significant, but their diagnosis using conventional imaging modalities like T2-weighted MRCP is challenging due to technical limitations. Recent consensus suggests using high-grade stricture (HGS) definitions on MRCP, yet these lack clear prognostic value. Gadoxetic acid-enhanced MRI offers functional imaging of bile excretion and may improve stricture assessment.

Data Highlights

A retrospective study included 172 PSC patients after exclusions. Gadoxetic acid-enhanced MRI was performed on a 3.0-Tesla system. The study assessed inter-reader agreement and prognostic value of PFS diagnosis on T1-weighted hepatobiliary contrast-enhanced MR cholangiography (T1-MRC) compared to DS and HGS on T2-MRCP, with ERCP as the gold standard.

Key Findings

• Potential functional strictures (PFS) are defined by impaired gadoxetic acid excretion on 20-minute hepatobiliary phase MRI, reflecting either true mechanical obstruction or hepatocellular dysfunction.
• PFS diagnosis demonstrated high inter-reader agreement, suggesting reproducibility and objectivity.
• PFS detection on T1-MRC may provide better prognostic information than DS or HGS assessments on T2-MRCP.
• Combining PFS identification with T2-MRCP morphology helps differentiate true biliary obstruction from advanced hepatic dysfunction in PSC.
• ERCP remains the gold standard for confirming stricture presence and severity but is invasive compared to MRI techniques.

Clinical Implications

Incorporating hepatobiliary contrast-enhanced MRI with gadoxetic acid into PSC evaluation allows functional assessment of biliary strictures, potentially improving early detection of clinically relevant strictures. This approach may guide timely interventions and better prognostication while reducing reliance on invasive ERCP. Radiologists and clinicians should consider adopting the PFS concept alongside morphological imaging for comprehensive PSC management.

Conclusion

The study supports the use of hepatobiliary contrast-enhanced MRI to identify potential functional strictures in PSC, offering a reproducible and prognostically valuable imaging biomarker. This functional imaging approach complements existing morphological criteria and may enhance clinical decision-making.

References

1. EASL/AASLD Guidelines 2018-2021 -- PSC Diagnosis and Management
2. International PSC Study Group 2021 -- Consensus on Dominant Stricture Definitions
3. MR Working Group of the International PSC Study Group 2021 -- Imaging Lexicon for PSC
4. Gadoxetic Acid MRI Studies 2007-2022 -- Functional Biliary Imaging in PSC