Gallstones form when cholesterol or bile, which is stored in the gallbladder, hardens into pieces of stone-like material.

• About 75% of all stones have solid cholesterol. They can either be pure (all cholesterol) or mixed (at least half cholesterol).
• About 20% are pigment gallstones made of calcium bilirubinate, a bile pigment. Some cholesterol may also be mixed in.
• About 5% are brown pigment stones which form in infected bile and are made of calcium bilirubinate plus calcium fatty acid soaps.
• 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.

Gallstones

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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:

• Biliary colic—Pain caused by a gallstone stuck in the bile duct, a tube that carries bile to the small intestine.
• Cholangitis—An infection of the bile ducts.
• Gallstone pancreatitis—A gallstone blocks the opening to the pancreatic duct, and digestive enzymes become trapped in the pancreas causing extremely painful inflammation.
• Rare complications include:
  • Gallbladder cancer
  • Complete blockage of the common hepatic duct, which drains bile from the liver
  • Gallstone ileus—The gallbladder attaches to the small intestine, creating an abnormal opening through which a large stone can travel and cause an obstruction of the small bowel
  • Formation of opening from the gallbladder to other nearby structures, like the intestines.

Gallstones are a common medical problem. About 10% to 25% of the adult population of the US 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.