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| Detailed Guide: Bile Duct Cancer |
What Are the Risk Factors for Bile Duct Cancer? |
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A risk factor
is anything that increases your chance of getting a disease such as
cancer. Different cancers have different risk factors. For example,
unprotected exposure to strong sunlight is a risk factor for skin
cancer and smoking is a risk factor for cancers of the lung, larynx,
colon, as well as many other organs. Researchers have identified
several risk factors that increase a person's chance of developing bile
duct cancer.
Disease of the bile ducts:
People who have chronic (long-standing) inflammation of the bile duct
have an increased risk of developing bile duct cancer. Sometimes this
inflammation occurs for no known reason and is called sclerosing cholangitis.
Cholangitis
is the medical term for bile duct inflammation. Sclerosing cholangitis
means that the bile duct inflammation leads to scar tissue formation.
Ulcerative colitis
is a condition that results in inflammation of the large intestine.
Some people with ulcerative colitis also develop sclerosing cholangitis
and are at increased risk of developing bile duct cancer.
Stones in
the bile duct, similar to, but much smaller than gallstones can also
cause inflammation that increases the risk of developing bile duct
cancer.
There are several other diseases of the liver and bile duct that
increase the risk of developing bile duct cancer. These include polcystic liver disease,
choledochal cysts, congenital dilation of the intrahepatic bile ducts
(also known as Caroli
syndrome), and cirrhosis
(damage to liver tissue that causes scar tissue formation in the
liver). Cirrhosis due to long-standing sclerosing cholangitis is more
likely to lead to bile duct cancer than cirrhosis from other causes. On
the other hand, cirrhosis caused by long-standing viral hepatitis has a
greater impact on a person's risk of developing hepatocellular cancer.
In Asian countries, infection by liver flukes, food- or water-borne
parasites 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: As in
most cancers, older people are more likely to get bile duct cancer.
More than 70% of patients with bile duct cancer are older than age 65.
Obesity:
Obesity: Being overweight can increase the risk of developing cancers
of the gallbladder and bile ducts. A big part of this association is
that obesity increases the risk of developing gallstones and bile duct
stones. However, there may be other ways that being overweight can lead
to bile duct cancers, such as changes in certain hormones.
Family
history: Although most bile duct cancers develop in people
without a
strong family history of this disease, this type of cancer is more
common in some families. Bile duct cancer is also associated with
inherited conditions (hereditary nonpolyposis colon cancer and familial
adenomatous polyposis) that can increase the risk of colorectal cancer.
Other factors:
A substance called Thorotrast
(thorium dioxide), which was used as a contrast agent in
x-ray diagnosis many years ago, can lead to bile duct cancer, as well
as to other types of liver cancer (hepatocellular
cancer and angiosarcoma).
For this reason, Thorotrast is no longer used. Other radioactive
chemicals also can be a risk factor. Other chemicals that may cause
this cancer include dioxin,
nitrosamines,
and polychlorinated
biphenyls (PCBs). Smoking may increase the bile duct
cancer
rate in people with sclerosing cholangitis.
Viral hepatitis:
Infection with either hepatitis B or hepatitis C virus has been linked
to intrahepatic cholangiocarcinoma. In a US study, the risk was about 6
times greater than normal in people infected with hepatitis C virus.
Non-viral cirrhosis:
This
is inflammation and scarring that occurs in the liver due to irritants
such as alcohol. A recent study found this to be a risk factor for
intrahepatic cholangiocarcinoma.
Revised: 04/17/2006
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