Sentence:  Portosystemic <WSD>shunts</WSD> can be congenital or acquired with congenital PSS commonly comprising a single communicating vessel between the portal venous circulation and the systemic circulation via the caudal vena cava or azygos vein. Of congenital <WSD>shunts</WSD>, 66–75% are extrahepatic. Intrahepatic portosystemic <WSD>shunts</WSD> are most commonly identified in larger breeds of dog (though we have also seen a number of terriers with intrahepatic <WSD>shunts</WSD> through our clinic). 
Meaning of the word marked with <WSD> tags:  An abnormal passage between body channels.