Gallstones

Gallstones are common in humans in developed countries.  Gallstones consist of small, hard, concretions, formed in the gallbladder. The majority are composed of cholesterol, (more than 50% cholesterol monohydrate crystals) and the rest are a mixture of calcium salts, and/or bile pigments. They are formed with progressing age, obesity and are associated with the female gender in humans. Genetic susceptibility and inborn errors of metabolism also contribute to the formation of gallstones. When cholesterol concentrations exceed the solubilizing capacity of bile, cholesterol can no longer remain dispersed and nucleates into solid cholesterol monohydrate crystals. Pigment gallstones are complex mixtures of abnormal insoluble calcium salts of unconjugated bilirubin along with inorganic calcium salts. Increased levels of unconjugated bilirubin result after infections of the biliary tract with bacteria or with parasites.There are rare reports of gallstones in chimpanzees.