Portal vein reflectors: duplex sonographic appearance

Duplex sonography has established utility in the noninvasive evaluation of the portal venous system. Recently, the duplex sonographic features of suspected portal venous air have been described. We report on an experimental study in dogs undertaken to establish if the same sonographic features could be reproduced in a laboratory setting and to determine if small fragments of clot emboli could produce similar gray-scale and Doppler findings. Injections of microbubbles of air and clot fragments into the portal venous system were monitored using duplex ultrasound. The gray-scale and Doppler features of flow in the main portal vein were indistinguishable in both microbubble and clot injections. Superimposition of high-amplitude spikes on the normal portal venous waveform was seen in 19 of 24 (79%) microbubble and 13 of 23 (56%) clot fragment injections. We conclude that the appearance of rapidly moving, bright intraluminal echoes coupled with spike-like aberrations of the portal venous waveform can be associated with portal venous air bubbles or small blood clot emboli.