Focal liver lesion: nonlinear contrast-enhanced ultrasound imaging

Enhancement Patterns of Benign Focal Lesions

Abscess

Abscesses of different etiology, pyogenic or amoebic, may present different features due to the varying degree of liquefaction and location. Furthermore, vascularity depends on evolution stage; usually it is located at the periphery of the lesion, whereas liquefied areas are positioned in the central zone. Conventional US can demonstrate an inhomogeneous echo-structure with peripheral hyper-echoic aspects and central hypo-echoic features. Color Doppler may detect vascular signals at periphery or in the septa of the lesion. Contrast-enhanced ultrasound shows as described below (Catalano et al., 2005):

• Typical features:
  • Arterial phase: rim enhancement, no enhancement;
  • Portal Vein phase: hyper- / iso- enhancing rim, no central enhancement;
  • Parenchymal phase: hypo- enhancing rim, no central enhancement.
• Additional features:
  • Arterial phase: enhanced septa, hyper-enhanced liver segment;
  • Portal Vein phase: hypo- enhancing rim, enhanced septae.

Tuberculosis is an uncommon liver infection which occurs in the miliary form. On conventional ultrasound single or multiple hypo-echoic, well-defined nodules spread throughout the liver are generally observed (Brauner et al., 1989; Levine 1990). Contrast-enhanced ultrasound reveals hypo-enhancing well-defined nodules, especially in the later phase. Clinical findings are mandatory for the diagnosis (Akhan and Pringot, 2002) and differentiation from hepatic metastases is necessary.