Noninvasive Insights: Magnetic Resonance Elastography and Ultrasound Liver Elastography for the Assessment of Liver Fibrosis in Fontan-Associated Liver Disease: A Comparative Study with Histology

The diagnostic performance of ultrasound (U/S) elastography and magnetic resonance elastography (MRE) of liver relative to histological assessment in Fontan patients remains uncertain. This study sought to evaluate the diagnostic accuracy and agreement of MRE and U/S elastography compared with histological congestive hepatic fibrosis score (CHFS) staging. We conducted a cross-sectional study in Fontan patients. Patients were categorized into non-significant fibrosis (≤ 2 A) and advanced fibrosis (≥ 2B) groups according to the CHFS scoring system. This study included 34 Fontan patients with a mean age of 20.2 ± 6 years, 23 (67.6%) had fibrosis ≥2B. The majority of whom had undergone an extracardiac conduit Fontan procedure. Hemodynamic parameters were similar between groups. MRE values were significantly higher in the fibrosis group (5.0 ± 0.9 vs. 4.1 ± 1.1 kPa, p = 0.018), whereas U/S elastography values did not differ significantly (p = 0.568). MRE demonstrated fair agreement with biopsy (quadratic-weighted κ = 0.468), while ultrasound showed no meaningful agreement (κ=-0.057). MRE demonstrated acceptable discriminative performance (AUC 0.77; 95% CI: 0.57-0.97), whereas ultrasound elastography showed poor discrimination (AUC 0.44; 95% CI: 0.21-0.66), both estimated from the continuous liver stiffness value in kilopascals; the two areas under the curve differed by 0.33 (95% CI: 0.06-0.60; DeLong p = 0.018). MRE demonstrates better agreement with histology and higher diagnostic performance compared with U/S elastography in Fontan patients. However, its discriminatory capacity, as reflected by AUC, remains lower than that reported in other chronic liver diseases. These findings highlight the unique pathophysiological substrate of Fontan-associated liver disease and underscore the need to establish disease-specific MRE cut-off values for each staging system to achieve more accurate fibrosis stratification and meaningful clinical application.