BIL-D | Direct Bilirubin

Direct bilirubin (BIL-D) is the determination of the amount of conjugated (bound in the liver with glucuronic acid) bilirubin in the blood. Unlike indirect bilirubin, direct bilirubin dissolves in water, so it can be excreted through the bile ducts into the intestines and eliminated with urine. Under normal conditions, it enters the bloodstream only in very small amounts.

Increased direct bilirubin indicates that bilirubin metabolism is disturbed after its conjugation in the liver, usually due to bile drainage disorders or liver cell damage. This helps differentiate hepatic or obstructive jaundice from other forms of jaundice.

Test principle: The amount of direct bilirubin in serum is measured by spectrophotometric method. This test is usually performed together with the determination of total bilirubin, and indirect bilirubin is calculated as the difference between total and direct.

Recommendations:

• It is recommended to perform in case of jaundice, suspected liver diseases, bile duct stones, mechanical obstruction, acute viral hepatitis, cytomegalovirus infection, infectious mononucleosis.
• The test helps to evaluate whether increased total bilirubin is due to the conjugated (direct) or unconjugated (indirect) fraction.
• Used to monitor the course of liver diseases, especially in obstructive or infectious processes.
• It is recommended to be fasting for 8–12 hours before the test, avoiding alcohol and intensive physical activity.
• The test results should be evaluated together with other liver function markers and clinical data.