Risk stratification in primary sclerosing cholangitis: comparison of biliary stricture severity on MRCP versus liver stiffness by MR elastography and vibration-controlled transient elastography.

Objectives: To compare biliary stricture severity on magnetic resonance cholangiopancreatography (MRCP), magnetic resonance elastography (MRE), and vibration-controlled transient elastography (VCTE) liver stiffness (LS) for evaluation of risk stratification and prognostication in primary sclerosing cholangitis (PSC).

Materials And Methods: Eighty-seven patients (31-61 years; 34 female/53 male) prospectively underwent biochemical testing, VCTE, MRCP, and MRE between January 2014 and July 2016. Correlation between the MRCP grading of PSC based on biliary stricture severity, LS on MRE and VCTE, and the Mayo Risk Score as well as the Amsterdam Oxford Prognostic Index (AOPI) were evaluated and compared. Stricture severity was classified according to previous classification systems based on ERCP. Spearman's correlation and Kruskal-Wallis tests were performed.

Results: MRE-LS and intrahepatic stricture severity combined demonstrated higher discriminatory ability among risk categories based on Mayo Risk Score (AUROC = 0.8). MRE-LS alone demonstrated excellent discriminatory ability among risk categories based on AOPI using cutoffs of 1 and 2.7 and was superior to intrahepatic stricture severity (AUROC = 0.9, AUROC = 0.6-0.7). There was a weak correlation between intrahepatic stricture severity and MRE-LS (rho = 0.3; p = 0.011). VCTE-LS values were not correlated with stricture severity and were noncontributory to differentiate patients across risk groups. Intrahepatic stricture severity alone was a poor discriminator of advanced liver fibrosis on MRE (AUROC = 0.7); however, combining intra- and extrahepatic stricture severity and controlling for cholestasis and disease duration improved results (AUROC = 0.9).

Conclusion: This study demonstrates a significant discriminatory ability of LS values on MRE to distinguish between early to moderate and advanced liver fibrosis. LS values on MRE may add value to risk prognostication and further studies including clinical outcomes are needed.

Key Points: • Risk stratification was excellent for liver stiffness measurements on MRE and poor for VCTE and biliary stricture severity. • Risk stratification was further improved when liver stiffness measured on MRE was combined with intrahepatic and extrahepatic stricture severity and indicators of cholestasis were controlled for. • Liver stiffness measurements on MRE correlated with prognostic scores better than measurements performed on VCTE.