Bile is a yellow-brown fluid produced by the liver. The liver can produce as much as three cups of bile in 1 day, and at any one time, the gallbladder can store up to a cup of concentrated bile. As food passes from the stomach into the small intestine, the gallbladder contracts and sends its stored bile into the small intestine through the common bile duct. Once in the small intestine, bile helps digest fats in foods. Under normal circumstances, most bile is recirculated in the digestive tract by being absorbed in the intestine and returning to the liver in the bloodstream.
Gallstones are pieces of solid material that form in the gallbladder.
Gallstones form when substances in the bile, primarily cholesterol and bile pigments, form hard, crystal-like particles. Cholesterol stones are usually white or yellow in color and account for about 80 percent of gallstones. They are made primarily of cholesterol. Pigment stones are small, dark stones made of bilirubin and calcium salts that are found in bile. They account for the other 20 percent of gallstones.