Bilirubin, Direct

Bilirubin is a product of hemoglobin breakdown by the reticuloendothelial system and exists in two forms. Unconjugated (indirect) bilirubin is transported to the liver bound by albumin where it becomes conjugated (direct) with glucuronic acid and excreted. Elevated serum bilirubin is indicative of impairment of the liver, excessive hemolysis, or obstruction of the biliary tract.