The assessment of direct bilirubin is helpful in the differentiation of hepatic disorders. The increase in total bilirubin associated with obstructive jaundice is primarily due to the direct (conjugated) fraction. Both direct and indirect bilirubin are increased in the serum with hepatitis. In the newborn patient with hemolytic jaundice and neonatal jaundice, the increase in the total bilirubin is primarily due to the indirect (unconjugated) bilirubin fraction. This jaundice may be caused by Rh, ABO, or other blood group incompatibilities, by hepatic immaturity, or by hereditary defects in bilirubin conjugation.