Gallstones are formed within the gallbladder, an organ that stores bile excreted from the liver. Bile is a solution of water, salts, lecithin, cholesterol, and other substances. If the concentration of these components changes, they may precipitate from solution and form gallstones.
Gallstones may be as small as a grain of sand, or they may become as large as an inch in diameter, depending on how much time has elapsed from their initial formation.
Gallstones often have no symptoms and are usually discovered incidentally by a routine x-ray, surgery, or autopsy.
Gallstones are a common health problem worldwide. They are more common in women, and people over the age of 40.
Other risk factors include ethnic and hereditary factors, obesity, diabetes, liver cirrhosis, long-term intravenous nutrition and certain operations for peptic ulcers.