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Gallstones form in the gallbladder, a small organ located under the liver. The gallbladder aids in the digestive process by storing bile and secreting it into the small intestine when food enters. Bile is a fluid produced by the liver and is made up of several substances, including cholesterol, bilirubin, and bile salts.

What Are Gallstones?

Gallstones are pieces of solid material that form in the gallbladder. These stones develop because cholesterol and pigments in bile sometimes form hard particles.

The two main types of gallstones are:

  • Cholesterol stones: Usually yellow-green in color, approximately 80% of gallstones are cholesterol stones.
  • Pigment stones: These stones are smaller and darker and are made up of bilirubin.


What Causes Gallstones?

Several factors may come together to create gallstones, including:

  • Genetics
  • Body weight
  • Decreased motility (movement) of the gallbladder
  • Diet

Gallstones can form when there is an imbalance in the substances that make up bile. For instance, cholesterol stones may develop as a result of too much cholesterol in the bile. Another cause may be the inability of the gallbladder to empty properly.

Pigment stones are more common in people with certain medical conditions, such as cirrhosis (a liver disease in which scar tissue replaces healthy liver tissue) or blood diseases such as sickle cell anemia.

What Are the Risk Factors for Gallstones?

Risk factors for getting gallstones include:

  • Genetics. If other people in your family have had gallstones, you are at increased risk of developing gallstones.
  • Obesity . This is one of the biggest risk factors. Obesity can cause a rise in cholesterol and can also keep the gallbladder from emptying completely.
  • Estrogen . Estrogen can increase cholesterol and reduce gallbladder motility. Women who are pregnant or who take birth control pills or hormone replacement therapy have higher levels of estrogen and may be more likely to develop gallstones.
  • Ethnic background. Certain ethnic groups, including Native Americans and Mexican-Americans, are more likely to develop gallstones.
  • Gender and age. Gallstones are more common among women and older people.
  • Cholesterol drugs . Some cholesterol-lowering drugs increase the amount of cholesterol in bile, which may increase the chances of developing cholesterol stones.
  • Diabetes . People with diabetes tend to have higher levels of triglycerides (a type of blood fat), which is a risk factor for gallstones.
  • Rapid weight loss . If a person loses weight too quickly, his or her liver secretes extra cholesterol, which may lead to gallstones. Also, fasting may cause the gallbladder to contract less.
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