Focal nodular hyperplasia is the second most common benign solid hepatic focal lesion. It occurs more commonly in young women than men (2-4 females to 1 male ) in the third and fifth decade (Volk et al., 2001), and is a hypervascular hyperplasic lesion caused by preexisting vascular malformation. It is characterized by abnormally arranged hepatocytes, Kupffer’s cells, bile duct elements and vascularized fibrous septae. A peripheral pseudo capsule and a central or eccentric fibrous scar radiating to the periphery and containing arteries can be found. Usually it is smaller than 5 cm (Ros et al., 2001). On conventional US iso-, hypo-, hyper-echoic appearances may be found. A hypo-echoic stellate central scar can be identified in 18% of cases. Color Doppler can depict flow signals within the central and radiating vessels (Tanaka et al., 1990). Contrast- enhanced ultrasound may show typical and atypical features as described below (Migaleddu et al., 2004, Catalano et al., 2005).
Arterial phase: hyper-enhancing complete;
Portal Vein phase: hyper-enhancing;
Parenchymal phase: iso- hyper-enhancing.
Arterial phase:, early “central spider” or "spoke wheel” arteries and centrifugal filling , feeding artery;
Portal Vein phase: hypo- enhanced central scar;
Parenchymal phase: hypo-enhanced central scar.
Focal liver lesion between 2-3 segment, solid hypoechoic, show central vessels at color-power Doppler.
In arterial and portal phase show an hyper-enhancing complete, and in parenchymal phase iso-echoic enhancement to the rest of parenchyma.
In arterial phase early presence of a center-lesion vessel and aspect to spider central sign. In progressive portal phase enh of centrifugal type. In late parenchymal phase light hyper-enhancement regarding the surrounding parenchyma.