[Liver hyperdensity during arterial phase on CT exams]

The use of helical CT, infusing pump and non-ionic contrast media has enabled the evaluation of different hepatic circulatory phases during contrast injection. Starting the acquisition of scans 20 to 30 seconds after the injection at a rate of 3 to 4 ml/sec the arterial enhancing of the liver is depicted. THROMBOSIS OR COMPRESSION OF THE PORTAL VEIN: Hypervascular triangle-shaped was with peripheral base can be seen, secondary to the increased arterial flow to compensate for the diminished portal flow. ARTERIOPORTAL SHUNTS: This condition can be caused by tumors such hepatocellular adenocarcinomas and hemangiomas, trauma, interventional procedures, cirrhosis, AVMs and surgery. INFLAMMATORY LESIONS: Hypervascular areas can be seen during the arterial phase in abscesses or cholecystitis, returning to their normal condition in the arterial phase. ANATOMIC VARIANTS: Third veins coming from the periphery (capsular veins, accessory cystic vein and an aberrant gastric vein) supply enhanced blood earlier than the portal circulation. OTHER CAUSES: In liver cirrhosis diffuse hyperattenuated areas can be seen during the arterial circulation. In right-sided heart failure, pericardial disease and Budd-Chiari Syndrome, "mosaic areas" can also be noted. In other patients these perfusion disorders were considered unknown. TUMORS: The well-differentiated hepatocellular carcinoma is a lesion with a predominant arterial blood supply, thus appearing in general hyperdense in this phase. Hemangiomas may appear as highly hyperdense lesions in the arterial phase and can be misinterpreted as HCC if smaller than 2 cm. (30% of cases). Focal nodular hyperplasia is a benign lesion (vascular malformation associated with focal nodules of hepatocellular hyperplasia) with increased arterial blood supply. Hepatic adenomas show an important hypervascularity during the arterial phase and, if large, they may present a small central scar and or capsule. Low or high-grade dysplastic nodules can sometimes be seen as hypervascular areas during the arterial phase. Although most metastasis are depicted as hypodense lesions sometimes they can show arterial hypervascularity such as carcinoid and pancreatic islet cell metastasis.