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A risk factor is anything that affects your chance of gettinga
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.
- Ulcerative
colitis is a condition that results in inflammation of the
large intestine. Some people with ulcerative colitis also develop
inflammation in the bile duct, which puts them at increased risk for
bile duct cancer.
- 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.
- Other
abnormalities of the bile ducts: Some people have
abnormalities where the bile duct and pancreatic duct normally meet
that 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.
These people are at higher risk of bile duct cancer.
- Cirrhosis
is damage to the liver due to irritants such as alcohol and diseases
such as hepatitis that causes scar tissue to form. Some 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).
Liver fluke
infections
In
some Asian countries, infection by liver
flukes, which are food or water-borne parasite worms that invade the
bile duct, is a major cause of 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.
Aging
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.
Obesity
Being overweight or obese can increase the risk of developing
cancers
of the gallbladder and bile ducts. This may 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.
Family history
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.
Other possible
risk factors
Studies have found several other possible
risk factors for bile duct cancers. More research is needed to confirm
these possible links:
- Smoking
- Diabetes
- Pancreatitis (inflammation of the pancreas)
- Infection with hepatitis B virus or hepatitis C virus
- Exposure to asbestos
- Exposure to radon or other radioactive chemicals
- Exposure to dioxin, nitrosamines, or polychlorinated
biphenyls (PCBs)
Last Medical Review: 01/21/2010
Last Revised: 01/21/2010
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