Marker of liver and biliary tract disorders

Direct bilirubin is a compound of free bilirubin and glucuronic acid called bilirubin glucuronide. Direct bilirubin is synthesized in the liver, and then part of it is passed with bile into the small intestine. In case of hyperbilirubinemia, direct bilirubin accumulates in elastic tissue, mucous membranes, and skin. An increase in the level of direct bilirubin is observed in parenchymal and obstructive jaundice due to impaired bile flow. Patients with elevated serum levels of direct (bound) bilirubin have bilirubinuria.