Gallstones are small, hard deposits that form in your gallbladder. The gallbladder is a small, pear-shaped organ on the right side of your abdomen, just beneath your liver.

Gallstones occur when there's too much cholesterol or waste material in your bile, a digestive fluid produced by your liver.

Gallstones can be as small as a grain of sand or as large as a golf ball. Some people develop just one gallstone, while others develop many.

There are two types of gallstones:

  • Cholesterol stones. These are made up mostly of cholesterol. Cholesterol is a substance that's found in your blood and in all your body's cells. Your liver makes some cholesterol, and you get other cholesterol from the food you eat.
  • Pigment stones. These are made up of bilirubin, a yellow pigment that's a byproduct of the breakdown of red blood cells.

Most gallstones are cholesterol stones.

Gallstones can cause pain in your abdomen. If the stone moves into the duct that drains your gallbladder and liver, it can cause a blockage and severe pain.

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