Fontan-associated liver disease: a Croatian national experience and current clinical practice.

AIM: To assess the characteristics of patients with Fontan-associated liver disease (FALD) and its clinical correlates within contemporary multidisciplinary practice at the national tertiary referral center in Croatia. METHODS: This cross-sectional study included all adult patients with Fontan circulation followed at University Hospital Centre Zagreb between 2023 and 2025. Data from the most recent comprehensive cardiology and hepatology evaluation were analyzed. Liver assessment included laboratory testing, transient elastography, and structured imaging surveillance with alternating ultrasound and magnetic resonance imaging. Advanced FALD was defined as liver stiffness measurement (LSM)>22 kPa combined with indirect markers of portal hypertension. RESULTS: The study enrolled 37 adults (median age 24 years; 64.9% male), with a median of 21 years since Fontan completion. The median LSM was 18.5 kPa (interquartile range 14.6-23.1), and 27% of participants had LSM>22 kPa. Thrombocytopenia was present in 40.5% of patients. LSM was moderately negatively correlated with platelet count (Spearman's ρ=-0.490, P=0.0038). Conventional liver biochemistry was only mildly abnormal in most patients. One patient (2.7%) was diagnosed with hepatocellular carcinoma during surveillance and treated with locoregional therapy. CONCLUSION: FALD is common and clinically heterogeneous in adults with long-standing Fontan circulation, frequently affecting young patients decades after surgery. Conventional laboratory markers alone may underestimate disease severity. These findings support structured, multidisciplinary surveillance in this complex population. This first national experience from Croatia contributes region-specific data to the growing body of evidence on FALD.