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.

Some people with gallstones can also develop complications, such as inflammation of the gallbladder.

Gallstones are thought to develop because of an imbalance in the chemical make-up of bile inside the gallbladder. In most cases the levels of cholesterol in bile become too high and the excess cholesterol forms into stones.