What are the risk factors for bile duct cancer?
A risk factor is anything that affects your chance of getting a disease like cancer. Different cancers have different risk factors. For example, exposing skin to strong sunlight is a risk factor for skin cancer. Smoking is a risk factor for cancers of the lung, larynx (voice box), colon, bladder, kidney, and many other organs.
But risk factors don't tell us everything. Having a risk factor, or even several risk factors, does not necessarily mean that a person will get the disease. And many people who get the disease may not have had any known risk factors.
Researchers have found several risk factors that make a person more likely to develop bile duct cancer.
Certain diseases of the liver or bile ducts
People who have chronic (long-standing) inflammation of the bile duct have an increased risk of developing bile duct cancer. Several conditions of the liver or bile duct may cause this.
- Primary sclerosing cholangitis is a condition in which inflammation of the bile duct (cholangitis) leads to the formation of scar tissue (sclerosis) and an increased risk of bile duct cancer. The cause of the inflammation is not usually known. Many people with this disease also have inflammation of the large intestine called ulcerative colitis.
- Bile duct stones, which are similar to, but much smaller than gallstones, can also cause inflammation that increases the risk of bile duct cancer.
- Choledochal cysts are bile-filled sacs that are connected to the bile duct. (Choledochal means having to do with the common bile duct.) The cells lining the sac often have areas of pre-cancerous changes, which increase a person's risk for developing bile duct cancer.
- Liver fluke infections occur in some Asian countries when people eat raw or poorly cooked fish that are infected with these tiny parasite worms. In humans, these flukes live in the bile ducts and can cause bile duct cancer. There are several types of liver flukes. The ones most closely related to bile duct cancer risk are called Clonorchis sinensis and Opisthorchis viverrini. Liver fluke infection is rare in the US, but can affect people who travel to Asia.
- Abnormalities where the bile duct and pancreatic duct normally meet can allow digestive juices from the pancreas to reflux (flow back "upstream") into the bile ducts. This backward flow also prevents the bile from being emptied through the bile ducts as quickly as normal. People with these abnormalities are at higher risk of bile duct cancer.
- Cirrhosis is damage to the liver from irritants such as alcohol and diseases such as hepatitis that cause scar tissue to form. Studies have found it raises the risk of bile duct cancer.
Other rare diseases of the liver and bile duct that may increase the risk of developing bile duct cancer include polycystic liver disease and Caroli syndrome (a dilation of the intrahepatic bile ducts that is present at birth).
Inflammatory bowel disease
Inflammatory bowel disease includes ulcerative colitis and Crohn’s disease. People with these diseases have an increased risk of bile duct cancer. This is not explained by the link between ulcerative colitis and primary sclerosing cholangitis.
Older people are more likely than younger people to get bile duct cancer. More than 2 out of 3 patients with bile duct cancer are older than age 65.
Being overweight or obese can increase the risk of developing cancers of the gallbladder and bile ducts. This could be because obesity increases the risk of gallstones and bile duct stones. But there may be other ways that being overweight can lead to bile duct cancers, such as changes in certain hormones.
Exposure to Thorotrast
A radioactive substance called Thorotrast (thorium dioxide) was used as a contrast agent for x-rays until the 1950s and can lead to bile duct cancer, as well as to some types of liver cancer. This is why Thorotrast is no longer used.
A history of bile duct cancer in the family seems to increase a person's chances of developing this cancer, but the risk is still low because this is a rare disease. Most bile duct cancers are not found in people with a family history of the disease.
When taken together, the data from many different studies show that people with diabetes have a higher risk of bile duct cancer. This increase of risk is not high, and the overall risk of bile duct cancer in someone with diabetes is low.
Long term infection with either hepatitis B virus or hepatitis C virus increases the risk of intrahepatic bile duct cancers. This may be at least in part due to the fact that infections with these viruses can also lead to cirrhosis.
People who drink alcohol are more likely to get intrahepatic bile duct cancer. The risk is higher in those that have liver problems from drinking alcohol.
Other possible risk factors
Studies have found several other risk factors that might increase the risk of bile duct cancer, but the link between these risk factors and bile duct cancer is not as clear. They include:
- Pancreatitis (inflammation of the pancreas)
- Infection with HIV
- Exposure to asbestos
- Exposure to radon or other radioactive chemicals
- Exposure to dioxin, nitrosamines, or polychlorinated biphenyls (PCBs)
Last Medical Review: 10/30/2013
Last Revised: 10/30/2013