Cholesterol stones form in people who have an imbalance in the materials that make-up bile.
- There may be too much bilirubin and cholesterol, or not enough bile salts, compared to the amount of water in the bile. (Bile salts help to keep cholesterol dissolved in the bile.)
- Cholesterol stones also may form when the gallbladder does not empty normally, and the bile stands for long period of time.
- Pigment stones develop most often in people with cirrhosis, an inflammation of the liver; infections of the gallbladder; or inherited blood diseases, such as sickle cell anemia.
Several other factors increase the risk for gallbladder disease:
- Gender. Women between the ages of 20 and 40 are twice as likely to get
gallstonesthan men are. Estrogen, the female sex hormone, increases the amount of cholesterol in the bile. Extra estrogen from birth control pills or hormone replacement therapy may further increase bile's cholesterol content. It also may slow gallbladder emptying, allowing bile to stand for longer periods of time.
- Pregnancy. Estrogen levels increase during pregnancy. The risk may increase with the number of pregnancies, since women who have been pregnant several times are at especially high risk for gallstones.
- Obesity. Being overweight tends to reduce the amount of bile salts in bile, so that less cholesterol can stay dissolved. Obesity also slows the rate at which the gallbladder empties. Some studies suggest that being even moderately overweight can increase the risk of gallstones.
- Rapid weight loss. "Crash diets" and fasting make the body burn, or metabolize, fat very rapidly. The liver reacts by releasing extra cholesterol into the bile. Fasting slows gallbladder emptying, since no food is present in the
small intestineto signal the need for bile.
- Age. Although gallstones occur in younger people, especially women, most cases are diagnosed in people over age 60.
- Ethnic heritage. Native Americans have the highest rate of gallbladder disease in the U.S. Mexican-Americans also have an unusually high risk. Scientists believe these groups have a genetic tendency to produce bile with large amounts of cholesterol.
- Taking cholesterol-lowering drugs. Drugs that lower blood cholesterol may increase the amount of cholesterol passed out of the body in the bile.