Your risk of developing cancer depends on many things including age, genetics, lifestyle and environmental factors. Anything that can increase your risk of cancer is called a risk factor.
Bile duct cancer is rare. It's slightly more common in men than women. Most bile duct cancers develop with no obvious cause. But there are factors that are known to increase risk, including conditions that cause long term (chronic) inflammation of the bile ducts.
Having one or more of the following risk factors doesn’t mean you'll definitely get bile duct 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 over 65. 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 with PSC have an increased risk of developing cancer of the bile ducts. Between 5 and 10 people out of 100 with PSC (5 to 10%) 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.
Less than 1 in 10 people with ulcerative colitis (less than 10%) also have 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. People with choledochal cysts have them from birth and most 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. 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 30 out of 100 people (30%) can 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 (intrahepatic bile duct cancer).
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, such as raw fish.
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.
Cirrhosis means scarring of the liver due to previous damage. This scarring can cause problems with the way the liver works. Having cirrhosis increases your risk of getting bile duct cancer. Cirrhosis can be caused by:
- infection with a virus such as hepatitis B or C
- long term alcohol drinking
Long term infection with the hepatitis B or C virus might increase the risk of developing bile duct cancer. These viruses cause damage to the liver (cirrhosis) and are also a known risk factor for primary liver cancer.
Thorotrast (thorium dioxide) is a contrast dye that was up until the 1950s to make x-ray pictures clearer. Exposure to thorotrast increases your risk of developing bile duct cancer. It's no longer used.
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.