Arterioportal communications: observations and hypotheses concerning transsinusoidal and transvasal types.

Arterioportal shunting is observed angiographically in a wide variety of pathologic conditions. The route of flow has classically been considered to be via the hepatic sinusoids (transsinusoidal). This route occurs in cases of cirrhosis or the Budd-Chiari syndrome, and results in retrograde hepatofugal flow in portal branches. More recently, a transvasal route has been recognized angiographically, in which portal flow often remains hepatopetal. The transvasal route occurs in cases of hepatocellular carcinoma, metastases, shock, hepatic arterial obstruction, and many other conditions. Histologic confirmation of this route has been sought for many years, with other partial success. Nevertheless, angiographic evidence, as presented here, is sufficiently compelling to justify description of this pathway and its significance. Arterioportal flow may also occur via a post-traumatic fistula (disruption of adjacent portions of hepatic artery and portal vein), and via benign tumor vessels in hemangioma or hemangioendothelioma.