BILIRUBINE Total & Direct 4 + 1 Approximately 80-85% of the bilirubin produced is deliver from the hemi moiety of the hemoglobin released from aging erythrocytes in the reliculoendothelial cells. Bilirubin, bound to albumin, is transported into the liver where it is rapidly conjugated with glucuronide to increase its solubility, then it is exvreted into billiary canaliculi, and hydrolyzed in the gastrointestinal tract. Unconjugated bilirubin serum concentration increase in case of overproduction of biliubin (a cute or chronic hemolytic anemias) and in case of disorders of bilibubin metabolism and transport defects ( impaired uptake by liver cells: Gilberts syndrome: defects in the conjugation reaction: Crigler-Najjar syndrome) Reduced excretion (hepatocellular damage: hepatitis cirrhosis …………Dubin Jonhson and Rotor syndrome) and obstruction to the flow of bile (most often produced by gallstones or by tumours) induce an important elevation of conjugated bilirubin and in aminor extent and increase of un conjugated bilirubin (conjugated hyperbilirubinemia).