Ultrasound Evaluation of Fontan-Associated Liver Disease: A State-of-the-Art Review

<b>Background</b>: Fontan-associated liver disease (FALD) is a progressive condition resulting from chronic hepatic venous congestion following the Fontan procedure for univentricular heart defects. As survival improves in these patients, recognition and management of FALD have become increasingly important. <b>Objective</b>: To describe the pathophysiological mechanisms, imaging findings, and diagnostic approach to FALD, with a focus on the role of ultrasonography, including contrast-enhanced ultrasound (CEUS). <b>Methods</b>: This narrative review explores the evolution of FALD through a multidisciplinary lens, integrating cardiovascular and hepatic imaging data. Particular attention is paid to Doppler ultrasound and CEUS, both in early parenchymal changes and in the differential diagnosis of potential complications such as hepatic nodules. <b>Results</b>: FALD is characterized by progressive fibrosis due to long-standing passive congestion, resulting in a wide spectrum of imaging findings. B-mode ultrasound reveals hepatomegaly, heterogeneous parenchyma, and gallbladder wall thickening. Doppler studies show altered hepatic venous flow patterns, while CEUS provides dynamic vascular evaluation, highlighting areas of altered perfusion. In advanced stages, hypo-vascular areas in the late phase may simulate malignant lesions, emphasizing the need for careful interpretation. The role of liver biopsy, though limited by invasiveness, remains crucial in selected cases. Surveillance strategies are not standardized but require close multidisciplinary follow-up. <b>Conclusions</b>: FALD presents complex diagnostic challenges requiring integrated imaging and clinical assessment. CEUS emerges as a valuable, non-invasive tool in characterizing hepatic congestion and guiding management. Increased awareness and standardized protocols are essential for early detection and tailored care in this growing patient population.