Budd-Chiari Syndrome: Ultrasound Patterns of Hepatic Veins
Terminology and Definition
Budd-Chiari Syndrome (BCS), synonym — hepatic venous outflow obstruction. It is defined as a global or segmental obstruction of venous outflow from the liver or inferior vena cava (IVC) at the level of major hepatic veins (HV) or suprahepatic IVC.
Ultrasound Findings in the Acute Phase
In the acute phase, BCS is characterized by:
- Absence or restriction of blood flow in the hepatic veins/IVC, possible thrombosis of HV/IVC.
- Intrahepatic collateralization, 'bicolor' hepatic veins: blood flow in opposite directions in HV branches sharing a common trunk.
- Decreased velocity and continuous (monophasic) flow in the portal vein, possible hepatofugal flow.
Chronic Phase and Interpretative Pearls
Key interpretative 'pearls': narrowed or obliterated HV/IVC; 'bicolor' HV due to intrahepatic collateralization on color Doppler. These patterns reflect redistribution of outflow through intrahepatic collaterals in the presence of major vein obstruction.
| Modality | Sign in BCS |
|---|---|
| Grayscale US | Narrowed/obliterated HV or IVC; possible thrombosis |
| Color Doppler US | 'Bicolor' HV (opposite directions in branches with a common trunk); intrahepatic collaterals |
| Pulsed Doppler US | Absence/restriction of flow in HV/IVC; in the portal vein — decreased velocity, continuous, possibly hepatofugal flow |
Hemodynamic Logic of Spectrum Reading
The vein spectrum reflects what is happening above and below the location point. Reversal of the S-wave in the hepatic vein suggests systemic congestion; decreased phasicity in the vein suggests proximal obstruction. In BCS, the flow should be read like a text: direction, velocity, and phasicity allow localization of the level of venous outflow obstruction.
Frequently asked questions
What are 'bicolor' hepatic veins and why are they important in BCS?
These are blood flows in opposite directions in branches of hepatic veins sharing a common trunk on color Doppler. This sign of intrahepatic collateralization is one of the key interpretative markers of BCS.
At what level does obstruction occur in Budd-Chiari Syndrome?
At the level of major hepatic veins (HV) or suprahepatic IVC; the obstruction can be global or segmental.
What flow changes in the portal vein are expected in the acute phase?
Decreased velocity and continuous (monophasic) flow in the portal vein, possibly hepatofugal flow.
How do hepatic veins appear in grayscale mode in BCS?
Narrowed or obliterated; possible thrombosis in HV or IVC, as well as visualization of intrahepatic collaterals.