What causes elevated direct bilirubin?

Direct bilirubin is a form of bilirubin produced in the liver when indirect (unconjugated) bilirubin undergoes glucuronidation. Elevated levels of direct bilirubin, medically known as hyperdirectbilirubinemia, typically indicate impaired hepatic excretion of bilirubin or obstruction in the biliary tract. Possible causes include liver diseases (such as hepatitis, cirrhosis, or intrahepatic and extrahepatic bile duct obstruction), gallstones, cholangitis, drug- or toxin-induced liver injury, and inherited disorders (such as Gilbert's syndrome or Dubin-Johnson syndrome). These conditions can impair the liver's ability to process bilirubin or obstruct bile flow, leading to increased levels of direct bilirubin. Physicians usually determine the underlying cause through detailed history taking, physical examination, blood tests (including liver function tests), and imaging studies (such as ultrasound, CT, or MRI), and then develop an appropriate treatment plan based on the diagnosis.