**3.1 Regenerative nodules (RN)**

These lesions are well defined, with isoechoic or hypoechoic appearance and sizes less than 1 cm. They are high in numbers and have a more or less uniform distribution, involving all liver segments. They can crowd resulting in large pseudo tumors. At Doppler examination, these nodules have no circulatory signal. CEUS exploration is indicated when a nodule is different against the general pattern of restructured liver either by different echogenity or by a different size than the majority of nodules. During the arterial phase, the signal is weak or absent. During the portal venous and late phase, the appearance is persistently isoechoic. Generally, RN is not distinct from the surrounding parenchyma. CEUS examination is useful to exclude an active lesion at the moment of exploration but does not have absolute prognostic value; therefore the patient should be periodically examined at short intervals (Kojiro, 2004; Bolondi et al, 2005). Correlation with clinical status and AFP measurements is required.

Fig. 9. Regenerative nodule (CEUS). One can see the hypovascular pattern of the solid nodule, with a size <10 mm.
