Lectures

Focal liver lesion: nonlinear contrast-enhanced ultrasound imaging

Enhancement Patterns of Benign Focal Lesions

Adenoma

Adenoma is an uncommon primary benign tumor that has hepatocellular origin. Young females who use hormonal medication are the most frequently affected patients (Karhunen, 1986). An adenoma may be asymptomatic or may present abdominal pain. This tumor has a marked tendency to intra-lesional or intra-abdominal high risk bleeding, although very rare potential malignant transformation could be considered. Hepatic adenoma presents (80% of cases) as a solitary well-defined or encapsulated tumor. This is a hypervascular lesion composed of cords of proliferating hepatocytes without portal venous tracts, terminal hepatic veins, and bile ductules, but with typical large sub-capsular tributary arteries originating from the hepatic arterial system. In larger masses necrotic and hemorrhagic changes are frequently observed (Ros et al., 2001, Bartolozzi et al., 2001). On conventional US, depending on lipid contents in the hepatocytes, HA appears as iso or Hyper-echoic a reasonably large, well-circumscribed focal lesion. When intralesional hemorrhages or necrosis occur, an inhomogeneous pattern is prevalent (Grazioli et al., 2000). Color Doppler demonstrates large peripheral sub-capsular arteries and veins (Golli et al., 1994). Contrast-enhanced ultrasound can be summarized as follows (Bleuzen and Tranquart, 2004; Catalano et al., 2005):

  • Typical features:
    • Arterial phase: hyper-enhancing, complete;
    • Portal Vein phase: hypo-enhancing;
    • Parenchymal phase: iso-enhancing.
  • Atypical features:
    • Arterial phase: non-enhancing areas (hemorrhage);
    • Portal Vein phase: hyper-enhancing, non-enhancing areas (hemorrhage);
    • Parenchymal phase: non-enhancing areas (hemorrhage).