A risk factor is anything that may increase your chance of having a disease. Risk factors for a certain type of cancer might include smoking, diet, family history, or many other things. The exact cause of someone’s cancer may not be known. But risk factors can make it more likely for a person to have cancer.

Things you should know about risk factors for cancer:

• Risk factors can increase a person's risk, but they do not necessarily cause the disease. 

• Some people with one or more risk factors never develop cancer. Other people can develop cancer and have no risk factors.

• Some risk factors are very well known. But there is ongoing research about risk factors for many types of cancer. 

Some risk factors, such as family history, may not be in your control. But others might be things you can change. Knowing the risk factors can help you make choices that might lower your risk. For example, if an unhealthy diet is a risk factor, you may choose to eat healthy foods. If excess weight is a risk factor, your healthcare provider may check your weight or help you lose weight.

Risk factors for gallbladder cancer include:

• Gallstones. This is the most common risk factor. At least 3 out of 4 people with gallbladder cancer also have gallstones and an inflamed gallbladder. Cancer is more likely to grow if you have one large stone rather than several small ones. Doctors believe that large gallstones grow over a long time, irritating the gallbladder wall and increasing the risk for cancer. Gallstones are common, but most people with gallstones don’t have gallbladder cancer.

• Porcelain gallbladder. The wall of the gallbladder becomes hardened from calcium buildup. The calcium buildup in the gallbladder changes how the gallbladder looks on X-rays. This is why it is called porcelain gallbladder. This condition can be linked with long-term (chronic) inflammation of the gallbladder (cholecystitis) from gallstones.

• Being female. Gallbladder cancer occurs more than twice as often in women as in men in the United States.

• Being an older adult. Gallbladder cancer occurs more often in people older than 65 years. But it can be found in younger people.

• Ethnicity. In the U.S., Hispanics of Mexican descent and American Indians have the highest rates of gallbladder cancer. African-Americans have the lowest rate. 

• Contact with carcinogens. Carcinogens are substances that can cause cancer. Toxic substances are often filtered by the liver and excreted into the bile. Bile flows through the gallbladder. This exposes the gallbladder to these substances. Workers in rubber plants and textile factories have a higher rate of gallbladder cancer. But because gallbladder cancer is relatively rare, it's hard to know if contact with the substances actually causes gallbladder cancer. 

• Obesity. Studies have shown a link between gallbladder cancer and obesity. This may be because obesity also increases the risk of gallstones. 

• Gallbladder polyps. Polyps are growths in the gallbladder wall. Polyps bigger than 1 centimeter (about 1/2 inch) are more likely to become cancer.

• Bile duct abnormalities. Bile ducts are tubes that carry bile from the liver and gallbladder through the pancreas to the small intestine. Bile is a liquid used by the body to break down fats in foods that you eat. Abnormal bile ducts may slow the flow of bile from the gallbladder or they may let pancreatic juices enter the gallbladder. This seems to increase the risk of gallbladder cancer. Cysts along the bile duct can also increase risk.

• Primary sclerosing cholangitis. This disease causes inflammation and scarring in the bile ducts and increases the risk of gallbladder cancer.

• Chronic typhoid or paratyphoid infection. If you have been regularly exposed to these infections, you have a higher risk of gallbladder cancer. Typhoid is very rare in the U.S.

• Family history. A family history of gallbladder cancer seems to raise a person's risk. But most people with gallbladder cancer do not have a family history of the disease. 

There are no routine tests to screen for gallbladder cancer. It’s a rare disease often confused with other more common gallbladder problems. People often don't notice any problems until the cancer is large or has spread. There are no blood tests to find gallbladder cancer. It's often hard to see with ultrasound or CT scan. This makes it hard to find the cancer early. Talk with your healthcare provider about your risk factors for gallbladder cancer and the best ways to reduce your risks.