Bile Metabolism and Lithogenesis: An Update.

Bile is composed of multiple macromolecules, including bile acids, free cholesterol, phospholipids, bilirubin, and inorganic ions that aid in digestion, nutrient absorption, and disposal of the insoluble products of heme catabolism. The synthesis and release of bile acids is tightly controlled and dependent on feedback mechanisms that regulate enterohepatic circulation. Alterations in bile composition, impaired gallbladder relaxation, and accelerated nucleation are the principal mechanisms leading to biliary stone formation. Various physiologic conditions and disease states alter bile composition and metabolism, thus increasing the risk of developing gallstones.