Cavernous transformation is a sequela of portal vein thrombosis and implies the formation of porto-portal collaterals in the setting of acquired, benign portal vein thrombosis (figure 4). It seldom occurs in patients with hepatocellular carcinoma. It can develop as early as 6 to 20 days after the thrombotic event. Collateral vessels are thought to originate from paracholedochal (bile duct wall) veins, periportal veins originating from around the pancreatic head, the blood vessels of the portal vein wall, or re-canalization of the portal vein itself. Color Doppler findings include non-visualization of the extrahepatic portal vein and/or its branches with the formation of innumerable periportal collateral vessels. These vessels frequently extend intrahepatically around the thrombosed portal vein branches. Doppler analysis shows a portal vein-like waveform. Patients with portal vein thrombosis and cavernous transformation not only develop portosystemic collaterals, (most commonly a left coronary vein or perisplenic veins), but also develop porto-portal collaterals. Reversed flow may also develop in a patent portal vein branch to supply an area with portal vein thrombosis. Pericholecystic veins may also develop to supply the posterior aspect of the right lobe of the liver.
