The bilirubin level does not usually rise above 200 μmol/L and the baby remains well. The condition requires early surgical treatment to avoid the need for liver transplantation. Their bodies cannot keep up with this breakdown and the patient becomes jaundiced as a result. This condition is called jaundice (icterus). Unconjugated bilirubin is fat soluble however conjugated bilirubin is water-soluble and hence can be excreted through kidneys. Bilirubin passes through two phases. The unconjugated bilirubin builds up in the body giving liver failure patients their yellow glow. Unconjugated bilirubin also known as indirect bilirubin, is a fat-soluble form of bilirubin that is formed during the initial chemical breakdown of hemoglobin and while being transported in the blood, is mostly bound to albumin to the liver. If the conjugated bilirubin levels are higher than the unconjugated bilirubin, this is typically due to a malfunction of the liver cells in conjugating the bilirubin.
Malformation of the bile ducts (biliary atresia) obstructs the flow of bile, damaging the liver and causing raised concentrations of conjugated bilirubin. The unconjugated bilirubin is then sent to the liver, which conjugates the bilirubin with glucuronic acid, making it soluble in water. Unconjugated bilirubin is a waste product of hemoglobin breakdown that is taken up by the liver, where it is converted by the enzyme uridine diphosphoglucuronate glucuronosyltransferase (UGT) into conjugated bilirubin. Jaundice is the discoloration of body tissues caused by abnormally high blood levels of bilirubin.
It has been shown that bilirubin production in a term newborn is 2-3 times higher than in adults. Jaundice is a yellowish discoloration of the skin and sclerae that is an important symptom of elevated serum bilirubin, which is caused by an abnormality of bilirubin metabolism or excretion.
It can be caused by many disorders ranging from benign to life-threatening conditions such as Gilbert's syndrome and pancreatic cancer respectively.
Upon increase of serum bilirubin between 22-35 mmol/l, some people may notice slightly yellowish sclera pigmentation, referred to as a subicterus. However, the bilirubin level may go much higher if the baby is premature or if there is increased red cell breakdown - eg, extensive bruising, cephalohaematoma. Direct & Indirect Bilirubin. Hemolytic anemia: Some patients have a rapid destruction of red blood cells. Bilirubin in this phase is called “indirect” or “unconjugated” bilirubin . Most of this conjugated bilirubin goes into the bile and out into the small intestine. Unconjugated bilirubin still produces Azobilirubin whereas conjugated bilirubin only produces it if dye is added.
Indirect and direct bilirubin together make up total bilirubin. Indirect bilirubin is the unconjugated form of bilirubin in the blood. Jaundice is a leading, though sometimes late, symptom in most diseases of the liver, gallbladder ducts, hemolytic anemias, and many inborn and acquired disorders of bilirubin metabolism. Similarly, the causes of pathologic unconjugated hyperbilirubinemia are also due to increased bilirubin production, decreased bilirubin clearance, and increased enterohepatic circulation. Gilbert's syndrome is a common cause of isolated unconjugated hyperbilirubinemia, and is the most common cause of hereditary jaundice [Sticova and Jirsa, 2013]. It is carried from the blood to the liver where it is conjugated to its direct form and excreted into the intestines.