Budd-Chiari Syndrome

General characteristics

Budd-Chiari Syndrome Budd-Chiari syndrome is a disorder with numerous causes, resulting from obstruction to hepatic venous outflow.

Morphology

Obstruction of venous outflow from the liver results in portal hypertension, ascites, and progressive hepatic failure. Causes of intraluminal venous obstruction include polycythemia vera, pregnancy, postpartum state and intra-abdominal cancer, especially HCC.

Budd-Chiari syndrome most often results in atrophy of peripheral liver, which experiences severe venous obstruction, and hypertrophy of the caudate lobe and central liver, which are relatively spared.

Absence of hepatic veins may be demonstrated by time-of-flight techniques or portalphase gadolinium-enhanced gradient-echo sequences. Generally, a combination of both approaches results in the highest diagnostic accuracy. However, bright-blood technique is the most accurate and usually suffices. On immediate post-gadolinium MR images, the peripheral atrophic liver in Budd-Chiari syndrome may enhance to a greater or lesser extent than normal or hypertrophied liver, which provides insight into the chronicity of the disease process.

Acute-onset Budd-Chiari

In acute-onset Budd-Chiari syndrome, the peripheral liver enhances less than central liver. This is associated with moderately high signal intensity on T2-weighted images and low signal intensity on T1-weighted images reflecting associated edema.

Subacute Budd-Chiari syndrome

In subacute Budd-Chiari syndrome, reversal of flow in portal veins and development of small intra- and extrahepatic venovenous collaterals occurs. Many of the collaterals are capsule-based. Signal of the peripheral liver is mildly increased on T2-weighted images and mildly decreased on T1-weighted images, similar to acute Budd- Chiari syndrome. On dynamic gadolinium-enhanced MR images, mildly increased and heterogeneous enhancement is apparent in the peripheral liver relative to central liver on hepatic arterial dominant-phase images that, over time, becomes more homogeneous with the remainder of the liver. Caudate lobe hypertrophy is mild to moderate, and collateral vessels are not prominent in the subacute setting (Noone et al. 2000).

In chronic Budd-Chiari syndrome, hepatic edema is not a prominent feature and fibrosis develops. Fibrosis results in decreased signal of peripheral liver on T2- and T1-weighted images. Enhancement differences between peripheral and central liver on serial post-gadolinium images become more subtle.

Venous thrombosis, appreciated in acute and subacute disease, is usually not observed in chronic disease. Massive caudate lobe hypertrophy, massive enlarged bridging intrahepatic collaterals, extrahepatic collaterals, and regenerative nodules are all features observed in chronic Budd-Chiari syndrome. Curvilinear intrahepatic collaterals and capsule-based collaterals are characteristic of chronic Budd-Chiari syndrome.

Varices are usually prominent in chronic Budd- Chiari syndrome and are well shown on interstitial-phase fat-suppressed images. Extensive portosystemic varices, as observed in other chronic liver diseases, are also present.

The development of nodular regenerative hyperplasia in the chronic setting is the result of hepatic ischemia caused by hepatic venous obstruction. The nodules are isointense or of low signal intensity on T2-weighted images, and have high signal intensity on T1-weighted images similar to macroregenerative nodules. These nodules reveal moderately intense enhancement on immediate postgadolinium gradient-echo images (Noone et al. 2000).