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State-of-the-art magnetic resonance (MR) imaging using tissue specific contrast media facilitates detection and characterization in most cases of hepatic nodules. According to the currently used nomenclature, in liver cirrhosis there are only two major types of hepatocellular nodular lesions: regenerative lesions and dysplastic or neoplastic lesions. The purpose of this clinical imaging review is to provide information on the properties of tissue-specific MR contrast agents and on their usefulness in the demonstration of the pathologic changes that take place at the level of the hepatobiliary and reticuloendothelial systems during the carcinogenesis in liver cirrhosis.

In this educational presentation, we offer an overview of acquired anomalies of the portal venous system explored by biphasic helical CT and MRI. Portosystemic collateral vessels, cavernous transformation of the portal vein, intrahepatic vascular shunts, aneurysms of the portal venous system, thrombosis of the portal venous system, and gas in the portal venous system will be discussed. For liver surgery and interventional procedures it is necessary to have a correct mapping of normal anatomy, variants, and different pathologies involving the portal venous system.

The liver has a unique dual blood supply from the hepatic artery (25%) and the portal vein (75%). Helical computer tomography (CT) and also magnetic resonance imaging (MRI) are suitable techniques for hepatic imaging. Helical CT and MR angiography allow single breath-hold scanning without motion artifacts. This article illustrates helical CT and MRI findings of different types of hepatic perfusion disorders. Because of rapid image acquisition, three-phase (hepatic arterial phase, portal venous phase and parenchymal phase) CT or MR-angiography evaluation of the hepatic parenchyma is possible, improving perfusion disorders evaluation, tumors detection and characterization in a single study. We classified hepatic perfusion abnormalities in: portal disorders, arterial disorders, hepatic veins abnormalities, intrahepatic vascular communication, hepatic lesions and perfusion disorders and other causes. Differential diagnosis and pitfalls of these entities must be known for a correct diagnosis of focal hepatic lesions.