Liver tumors are often incidentally found during ultrasound examinations. The decision on further diagnostic imaging depends on the clinical context and the appearance in B mode ultrasound. This review highlights the role of grey scale and contrast-enhanced ultrasound (CEUS) and summarizes the ultrasonographic key features of the most common benign and malignant liver tumors. Conventional grey scale ultrasound is recommended in several guidelines for screening and follow-up of liver tumors in certain risk populations but its ability to characterize liver tumors is limited in most cases. The CEUS has an excellent tolerability and enables liver tumor characterization with a high sensitivity and specificity. The diagnostic value of CEUS is comparable to magnetic resonance imaging. In the case of unclear lesions, inconclusive findings by different imaging methods or if molecular targeted treatment is pursued, ultrasound-guided biopsy is often mandatory. Ultrasound is a rapidly and ubiquitously available method for the detection of liver tumors and CEUS is the only imaging method that enables real-time examination of all contrast phases in the liver. It should therefore be used as the first line imaging method for liver tumor characterization.
Keywords: Contrast-enhanced ultrasound; Focal nodular hyperplasia; Hemangioma; Hepatocellular adenoma; Hepatocellular carcinoma.