- Gallstones are composed of either cholesterol, bile pigment, or, more commonly, a mixture of these two constituents.  Cholesterol stones form due to an altered composition of bile resulting in the precipitation of cholesterol crystals.  Most gallstones are asymptomatic; however, when they migrate down the biliary tree they can be responsible for a diverse array of complications such as: acute cholecystitis, biliary colic, cholangitis and pancreatitis.