MR angiography appears to offer a noninvasive method of evaluating the intra- and extrahepatic collateral pathways. Identification of intrahepatic collateral veins (Figs. 6
) is highly suggestive of Budd-Chiari syndrome [3
]. The intrahepatic collateral vessels divert blood away from the occluded hepatic vein and drain into a patent hepatic vein or a systemic vein. They can be identified by their typical tortuous course or curvilinear configuration.
The sites of extrahepatic collateral veins in Budd-Chiari syndrome are generally different from those collaterals localized at the portosystemic communication sites in cirrhosis. Extrahepatic systemic venous collateral routes in Budd-Chiari syndrome can be evaluated in four groups according to the classification proposed by Cho et al. [7
]. In Budd-Chiari syndrome, deep and central tributaries of the systemic circulation (i.e., ascending lumber veins, vertebral venous plexus, and azygos and hemiazygos veins) are the most commonly collateralized routes (Fig. 8
). The other collateral vessels seen in this syndrome are the left renal—hemiazygos pathway (Fig. 9
), inferior phrenic—pericardiophrenic collaterals (Fig. 8
), and superficial collaterals of the abdominal wall (Fig. 10
). Although collateralized abdominal wall veins are seen even at physical examination of patients, this finding may not be displayed on MR angiograms because of the limited size of the selected imaging volume.