Diagnostic approach to focal liver lesions at cross-sectional imaging: a primer for beginners

Liver imaging encompasses a broad spectrum of diseases in different clinical backgrounds. The available literature is vast and reported data often lacks standardization. Because of all these issues, the differential diagnosis and the characterization of liver lesions can be challenging for the beginner. The aim of this narrative review is to provide the basics for an algorithm approach to liver lesions on cross-sectional imaging. First, some tips for the optimization of Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) protocols will be provided. Liver Imaging Reporting and Data System (LI-RADS, version 2018) working group is proposing the adoption of their standardized lexicon beyond the original target population of LI-RADS (i.e., liver cirrhosis). Thus, the main imaging findings will be defined following the LI-RADS lexicon. Since the contrast study is the most important for lesion characterization, this narrative review separates the lesions into avascular, hypovascular, and hypervascular, with a focus on chronic liver disease (CLD) and hepatocellular carcinoma (HCC).