Gallstones are small stones, usually made of cholesterol, that form in the gallbladder. In most cases they don't cause any symptoms and don't need to be treated. However, if a gallstone becomes trapped in a duct (opening) inside the gallbladder it can trigger a sudden intense abdominal pain that usually lasts between 1 and 5 hours. This type of abdominal pain is known as biliary colic. Some people with gallstones can also develop complications, such as inflammation of the gallbladder (cholecystitis), which can cause: persistent pain jaundice a fever