Ultrasound of Hepatocellular Carcinoma: The Important Contribution of Contrast Enhancement

Ultrasound is established as a screening method in the patient at high risk for hepatocellular carcinoma. US detection of a nodule in such a patient is frequently followed by contrast-enhanced ultrasound (CEUS) performed with the addition of a microbubble contrast agent. This allows for the evaluation of the mass in a similar manner to that on CT and MR scan where liver mass diagnosis is based on the enhancement characteristics of the mass in the arterial and portal venous phases. CEUS plays an integral role with CT and MR scan in the evaluation of the patient at risk for hepatoma. The classic enhancement characteristics of arterial phase hypervascularity and portal phase washout are shown in the majority of patients. However, well recognized is arterial phase hypovascularity and lack of washout in the portal phase especially in well-differentiated tumors. The real-time nature of CEUS gives it a unique role in the evaluation of small tumors in particular. Its versatility of performance is also invaluable for monitoring RFA and showing response to therapy.