Hepatic outflow obstruction: enhancement patterns of the liver on MR angiography

Our purpose was to present the enhancement patterns of the liver on MR angiography in patients with hepatic outflow obstruction. Twenty-three patients with Budd-Chiari syndrome (4 in acute stage and 19 in chronic stage of the disease) were examined with 3D contrast-enhanced MR angiography. During early and late portal venous phase of MR angiography the pattern of parenchymal enhancement was assessed on source images. The enhancement patterns were evaluated under 4 groups as following: (a) central (b) peripheral (c) patchy and (d) homogeneous enhancement. The morphologic changes in the liver (lobar hypertrophy or atrophy, hepatic surface irregularities) were also recorded. In the acute stage global liver enlargement (75%) with caudate hypertrophy (100%) and central enhancement of the liver (75%) were suggestive findings of the hepatic outflow obstruction. The left lobe hypertrophy (53%) associated with the caudate lobe hypertrophy (72%) and irregular surface (26%) were predominant in the chronic stage of the disease. The enhancement patterns seen in chronic disease were variable and reflected the persistent stasis of the portal blood flow (patchy enhancement in 32% of the patients) or the altered hemodynamics of the liver due to the development of subcapsular collaterals (peripheral enhancement in 21% of the patients). Homogeneous enhancement of the liver in Budd-Chiari syndrome may indicate the chronicity of the outflow obstruction (37%) and shows a more stable hepatic perfusion that occurs after the formation of intra and extrahepatic collateral veins. The morphological and perfusional features on multiphase contrast-enhanced MR angiography are valuable in understanding the effects of the hepatic outflow obstruction on the liver parenchyma.