Beyond morphology: functional imaging of the liver with gadoxetic acid-enhanced magnetic resonance imaging.

Chronic liver diseases (CLD) are highly prevalent. Early diagnosis and staging of hepatic dysfunction are essential for optimal treatment decisions. While conventional imaging primarily evaluates morphology and focal liver lesions, gadoxetic acid (GA)-enhanced magnetic resonance imaging (MRI) provides additional functional information by assessing hepatocellular uptake and biliary excretion. Hepatocyte uptake depends largely on sinusoidal membrane transporters (OATP1B1/1B3), while excretion into bile canaliculi is mediated by MRP2. In liver dysfunction and cirrhosis, both processes may be impaired, resulting in measurable changes on hepatobiliary phase (HBP). This review summarizes the biological rationale, MRI protocol, and quantitative indices, including RLE, REI, HUI, rHUI, SIR, CUI, LSI, as well as the qualitative Functional Liver Imaging Score (FLIS). It also highlights key clinical applications, including prognostication in advanced CLD, preoperative risk stratification for post-hepatectomy liver failure, evaluation in the setting of embolization and locoregional therapies, and transplant assessment, along with emerging roles in metabolic dysfunction-associated steatotic liver disease. Finally, future directions are discussed, including T1 mapping and AI-based whole-liver quantification.