Gallstones form when cholesterol or bile, which is stored in the gallbladder, hardens into pieces of stone-like material. Gallstones are made of about 75% cholesterol salts. The remaining 25% is made up of bilirubin salts, a bile pigment and calcium carbonate. Gallstones can be as small as a grain of sand or as large as a golf ball. The gallbladder can develop just one large stone, hundreds of tiny stones, or almost any combination.
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Gallstones can block the normal flow of bile if they lodge in any of the ducts that carry bile from the liver to the small intestine. Bile trapped in these ducts can cause inflammation in the gallbladder, the ducts, or, rarely, the liver.
Gallstones can cause several related problems including:
Gallstones are a common medical problem. About 10% to 15% of the adult population of the United States has gallstones. However, about 80% of people who have gallstones have no symptoms. This condition is referred to as silent gallstones and usually does not require treatment.
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Gallstones. EBSCO DynaMed website. Available at:
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Updated October 23, 2013. Accessed December 5, 2013.
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Last reviewed September 2014 by Michael Woods, MD
Last Updated: 9/17/2014