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Understanding Gallstones -- the Basics


About a million new cases of gallstones are diagnosed in the U.S. each year. For reasons that are still unclear, women are two times more likely than men to be afflicted. Native Americans have the highest rates of gallstones in the U.S. because they have a genetic disposition to secrete high levels of cholesterol in bile (a contributing factor to gallstones.) Mexican-Americans also have high rates of gallstones.

Gallstones are also more common in people over the age of 60, in those who are obese or have lost a lot of weight in a short amount of time, in those who have diabetes, and in women who have had multiple pregnancies and who take hormone replacement therapy or birth control pills.

What Causes Gallstones?

The primary function of the gallbladder is to store bile, a brown or yellowish fluid that helps the body break down fatty food. When you eat a meal, the gallbladder releases its stored bile into the cystic duct. From there the fluid passes through the common bile duct and into the small intestine to mix with food.

Chief among the ingredients of bile are cholesterol and bile acids. Normally, the concentration of bile acids is high enough to break down the cholesterol in the mixture and keep it in liquid form. However, a diet high in fat can tip this delicate balance, causing the liver to produce more cholesterol than the bile acids are able to handle. As a result, some of this excess cholesterol begins to solidify into crystals, which we call gallstones. About 80% of all gallstones are called cholesterol stones and are created this way. The remaining 20% consist of calcium mixed with the bile pigment bilirubin and are called pigment stones.

Gallstones can form even in people who eat properly. And as researchers have found, a diet extremely low in fat can also contribute to gallstone formation: With little fatty food to digest, the gallbladder is called into play less frequently than usual, so the cholesterol has more time to solidify. Other factors that can reduce activity in the gallbladder, possibly leading to gallstone formation, include cirrhosis, the use of birth control pills or hormone replacement therapy, and pregnancy.

Family history, diabetes, sudden weight loss, and cholesterol drugs, and older age can also increase risk for gallstones.

WebMD Medical Reference

Reviewed by Jennifer Robinson, MD on March 07, 2015
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