Hepatic perfusion and hemodynamic effects of transjugular intrahepatic portosystemic shunts.

The liver depends on a dual blood supply from the hepatic artery and the portal vein. The normal liver receives 70% portal flow and 30% hepatic arterial flow, with most arterial blood feeding the biliary tree. As cirrhosis robs the liver of its regenerative capacity, the portal flow decreases and intrahepatic portosystemic shunting increases with a variable increase in arterial flow across arterioportal shunts. This compensation mechanism attempts to reperfuse remaining sinusoids. Transjugular intrahepatic portosystemic shunts (TIPS) or surgical portosystemic shunts may acutely diminish portal perfusion further, leading to hepatic failure. Small-diameter TIPS or surgical shunts reduce the incidence of complications by preserving nutritive portal flow. Although the inverse relationship of arterial and portal flow is physiologically valid, there is individual variation in the ability to substitute one blood supply for another. This variability may result from anatomic or functional factors influencing the flow across arterioportal shunts. Hepatic perfusion curves derived from enhanced imaging studies can subtype cirrhotic patients into favorable versus unfavorable perfusion patterns. Patients with high arterial flow to the liver or patients with retained portal-type flow curves have better survival and morbidity compared with those patients with unfavorable flow manifest by diminished arterial-type curves on hepatic perfusion analysis.