Ultrasound (US)

Ultrasound in routine sonographic examination of the liver allows a resolution of about 1 mm in the axial plane and 2 mm in the longitudinal plane. The maximal deepness to be reached is about 150 mm. The entire liver should be covered in two different planes, but there are still potential “blind spots” such as lesions that lie in deep areas of the liver under the diaphragm or on the surface of the liver.

Ultrasound of the liver (HCC). Courtesy of Dr. Grazioli, Brescia, Italy

Evaluation technique with US

Focal liver lesions can be evaluated by their echogenic characteristics, the distribution into the segmental model (liver segments after Couinaud), and the possible invasion of vascular structures. Doppler US, contrast-enhanced US, tissue harmonic imaging (THI) and 3D US systems can provide further information to detect and characterize focal liver lesions (Hamer et al., 2007). The prerequisite for a successful diagnostic abdominal US examination is a careful preparation of the patient. The examination time depends largely on the investigator’s skill and experience and usually should not exceed 10-15 min even in difficult-to-scan patients.

Benefits	Drawbacks
Low cost Ease of use Versatility and wide availability Color and duplex Doppler Possible demonstration of vascular involvement Hemodynamic information can be obtained noninvasively Simple	Dependence on investigator’s skill Sometimes lack of reproducibility Limitations for obtaining adequate imaging results Blind spots Lower diagnostic ability