What happens normally?

A lot of blood passes through the liver. It flows out through the hepatic veins and into the inferior vena cava. This is a large blood vessel that carries blood back to the heart.

What goes wrong in Budd-Chiari syndrome?

In Budd-Chiari syndrome, the blood flow out of the liver is partially blocked. This is sometimes called ‘an obstruction of hepatic venous outflow’.

This means blood is flowing into the liver faster than it can flow out. So blood build-ups (congestion) in the liver. The liver becomes swollen, and this can cause tenderness or pain. It can also cause complications such as ascites (swelling of the tummy caused by fluid build-up).

Back to top

What causes Budd-Chiari syndrome?

There are two types of Budd-Chiari syndrome.

Primary Budd-Chiari syndrome

Primary Budd-Chiari syndrome is caused by a problem with blood clotting. Or by inflammation of the blood vessels.

Your blood needs to be able to flow freely through your body. But it also needs to form clots quickly when you get a cut or bruise.

A complicated system balances these two different needs. It has lots of different parts and usually they work well together. But a problem with any one of them could affect the whole system.

In some cases, this can mean there are dangerous blood clots where they are not needed. This is called thrombotic disease. Clots in blood vessels are called thromboses.

There are lots of different causes of thrombotic disease. In some cases, it might be a problem in the genes passed down in the family. Finding the cause might be helpful for treatment. But it is not always possible.

Some inflammatory conditions are also linked to Budd-Chiari syndrome. This includes:

• Behçet disease
• Sjögren syndrome

• inflammatory bowel disease (IBD)

Secondary Budd-Chiari syndrome

The other type of Budd-Chiari syndrome is called secondary Budd-Chiari. This is caused by something pushing on the veins from outside.

This can include:

• a type of liver cancer called hepatocellular carcinoma (HCC)
• very large liver cysts or abscesses
• large benign liver tumours

A number of other conditions or factors are linked to BCS, including:

• pregnancy
• high-dose oestrogen from using oral contraception.

But in some cases the cause of Budd-Chiari syndrome is unknown.

Back to top