What does it mean when direct bilirubin levels are elevated?

Direct bilirubin is a component of total bilirubin. A marked elevation in direct bilirubin relative to total bilirubin suggests possible biliary tract injury—either intrahepatic or extrahepatic. Intrahepatic bile duct injury, known as cholestasis, is often caused by damage to the small bile ducts due to drugs, viral infections, or autoimmune factors; this condition may sometimes be accompanied by elevated transaminase levels. Extrahepatic biliary obstruction is another possibility, which may result from conditions such as bile duct stones, cholangiocarcinoma, or pancreatic tumors compressing the common bile duct—any of which can lead to increased direct bilirubin levels.