Bilirubin is the catabolic product of heme, the oxygen binding complex of erythrocytes. Approximately in each 120 days, erythrocytes die and leave their contents into the bloodstream. Heme molecule is also released in the blood stream, to be converted to bilirubin. Bilirubin is not soluble in water, so it needs a glucuronic acid conjugation to become soluble in order to be clarified by the kidneys and intestines. This protein binding is realized in the liver from where it is secreted into the bile duct In this way, it is carried into the urine (urobilinogen) and feces (sterkobilinogen). After the conjugation with the protein, bilirubin is called ‘direct bilirubin’ (Conjugated bilirubin). Before the conjugation, it is called the ‘indirect bilirubin’ (Unconjugated bilirubin). Indirect bilirubin is bound to albumin in the blood. Direct+Indirect bilirubin gives Total Bilirubin.
Interpretation: Bilirubin is routinely excreted as the erythrocytes are degraded. After the heme in the erythrocytes is converted intobiliverdin an to bilirubin which is insoluble in water. It conjugates with albumin to be carried to the liver for conjugation with glukuronic acid. The albumin bound bilirubin is called the Indirect Bilirubin. This conjugation in the liver is for the excretion preocess through bile and to the urine and feces…If bilirubin amount exceeds liver conjugation capacity, indirect bilirubin increases in the bloodstream. This is either the increased production of bilirubin or decreased capacity of liver for conjugation. Neonatal jaundice, where liver conjugation enzmes are still immature, is an example of low liver conjugation capacity. This high indirect bilirubin values in newborns results in life threatening kernicterus. Unconjugated bilirubin can cross blood-brain barrier and deposit in the basal ganglia or cerebellum. Reduced hepatic blood flow (congestive heart failure and portosystemic shunt), liver diseases such as hepatitis, cryhosis, cancer of the liver and some drugs also represent decreased liver capacity for conjugation. Some types of inherited or acquired hemolytic anemias as large hematomas, dyserythropoesis (megaloblastic or sideroblastic anemias), Gilbert’s Syndrome, Crieglar Najar Syndromes type I and II result in increased unconjugated hyperbilirubinemia. High direct bilirubin levels, reflect high degradation of erythrocytes or high production of red blood cells due to hematological diseases Low values are nonimperpretable
Sample: Arm vein blood. Nonfasting
Working day: Everyday
Result Time: 2 hours
