Your risk of developing cancer depends on many factors. This includes things like whether you smoke and have a healthy balanced diet. And also genetic and environmental factors.
Anything that can increase your risk of cancer is called a risk factor.
Bile duct cancer is rare. Most bile duct cancers develop with no obvious cause. But there are factors that are known to increase the risk. This includes 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. It’s important to remember that bile duct cancer is rare, so the risk of developing it is still small.
Primary sclerosing cholangitis
Primary sclerosing cholangitis (PSC) is a rare type of inflammation of the bile ducts. Doctors don't know what causes PSC.
People with PSC have an increased risk of developing cancer of the bile ducts. Between 5 and 35 out of 100 people with PSC (5 to 35%) go on to develop bile duct cancer.
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 ducts and fill up with bile. The cells that line the sacs can become abnormal. Doctors usually remove the cysts to reduce the risk of developing 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 (parasitic worms)
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 liver 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.
Bile duct stones (hepatolithiasis)
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 right and left hepatic ducts.
A medical dye called Thorotrast
Thorotrast (thorium dioxide) is a contrast dye that was used from 1930 to 1960 to make x-ray pictures clearer. Exposure to Thorotrast increases your risk of developing bile duct cancer. This type of dye is no longer used.
Where there isn’t clear evidence
Some factors might increase the risk of bile duct cancer but there isn’t enough evidence to be sure. These include:
- liver cirrhosis
- infection with the hepatitis B or C virus
- being overweight or obese
- drinking alcohol
- a family history of bile duct cancer
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.