Read about the risks and causes of bile duct cancer (cholangiocarcinoma).
What a risk factor is
Anything that can increase your risk of getting a disease is called a risk factor.
Different cancers have different risk factors. Having one or more of these risk factors doesn't mean you will get that cancer.
Your risk of getting bile duct cancer increases as you get older. It can develop at any age but most people who develop it are in their 60s and 70s. Remember, the risk is still small because this is a rare cancer.
Primary sclerosing cholangitis (PSC) is a rare type of inflammation of the bile ducts. We don't know what causes it. People who have this condition have an increased risk of developing cancer of the bile duct. Between 1 and 2 out of 10 people with PSC will go on to develop bile duct cancer.
Many years ago, doctors noticed that people with ulcerative colitis had a slightly increased risk of developing cancer of the bile duct. Around 1 in 200 people with ulcerative colitis develop it.
Up to 1 in 10 people with ulcerative colitis affecting the whole large bowel also have primary sclerosing cholangitis (PSC). Doctors now think it is more likely that the increased bile duct cancer risk is due to PSC rather than ulcerative colitis.
Choledochal cysts (pronounced kol-eh-doke-al sist) are very rare. You have them from birth. Most people born with choledochal cysts develop symptoms in early childhood. But some people do not develop any symptoms until adulthood.
Choledochal cysts are sacs that connect to the bile duct and fill up with bile. They grow slowly and can end up holding up to 2 litres of bile. The cells that line the sacs can be abnormal and occasionally show pre cancerous changes. If a surgeon does not remove the cysts, up to 2 in 10 people (20%) will go on to develop bile duct cancer.
Caroli’s disease is a similar condition to choledochal cysts. It is a very rare condition you are born with. It makes the bile ducts in the liver get wider (dilate). This can increase your risk of developing cancer in the bile ducts in the liver.
Liver flukes are parasitic worms that invade the bile ducts and increase the risk of bile duct cancer. They are not usually a cause of bile duct cancer in the UK. But flukes are a major problem in Asia where bile duct cancer is much more common. People get liver flukes through eating food that contains them.
Stones in the bile ducts can irritate the duct lining and cause inflammation. This can increase your risk of bile duct cancer. But the increase in risk is small.
Stones usually develop after infection or because of the slow movement of bile through the ducts. They tend to develop in the common or hepatic bile ducts.
Thorotrast (thorium dioxide) is a contrast dye that was used in the 1950s and 60s to make x-ray pictures clearer. Exposure to thorotrast increases your risk of developing bile duct cancer. It's no longer used.
There are a number of other factors that may be risk factors for bile duct cancer but we need more research to be sure. They include:
- liver cirrhosis
- hepatitis C infection
- HIV infection
- being overweight
- non cancerous (benign) growths in the bile duct called bile duct adenomas
- smoking tobacco
Other possible causes
Stories about potential causes are often in the media and it isn’t always clear which ideas are supported by evidence. There might be things you have heard of that we haven’t included here. This is because either there is no evidence about them or it is less clear.