At sonography, portal vein thrombus may appear echogenic, isoechoic, or anechoic, and may be obstructive or non-obstructive (figure 3). At color Doppler, there will be no detectable flow or partial flow if the thrombus is non-occlusive. It is important to always examine the vessels with gray scale before performing color Doppler so as not to miss a subtle non-occlusive thrombus.
When a portal vein thrombus is present, it is important to distinguish benign from malignant thrombosis. The presence of a hepatofugal arterial signal within the thrombus is very specific for a malignant thrombus and is due to tumor vessels growing into the portal vein. However, this finding is not always seen.
