Ultrasonography of portosystemic shunts in dogs and cats.

Ultrasonography is a rapid, accurate, noninvasive diagnostic test for primary (congenital) and secondary (acquired) portosystemic shunting in dogs and cats. Two-dimensional, gray-scale ultrasonography alone enables diagnosis of most congenital portosystemic shunts and determination of intra- versus extrahepatic location. Use of duplex- and color-flow Doppler ultrasonography aids detection of congenital and acquired extrahepatic portosystemic shunts. The underlying cause of acquired portosystemic shunting is portal hypertension; this may be documented by finding either hepatofugal or reduced velocity hepatopetal portal blood flow by duplex-Doppler. Also, ultrasonography may enable detection of lesions involved in the pathogenesis of portal hypertension, for example, hepatic arterioportal fistula, hepatic parenchymal lesions, and portal vein thrombosis.