Bilirubin

When bilirubin levels are high, in a condition called jaundice (a yellowing of the skin and the whites of the eyes), and further testing is needed to fin dout what is the cause. Too much bilirubin may mean that too many red cells are being destroyed, or that the liver can not remove all of the bilirubin from the blood.

It is not uncommon to see high bilirubin levels in newborn babies who are typically 1–3 days old, and then this conditions is called neonatal bilirubinaemia.  Withing the first 24 hours of life, up to 50% of full-term newborns, and an even greater percentage of pre-term babies, may have a high a bilirubin level. At birth, the newborn lacks the intestinal bacteria that help process bilirubin. This is not abnormal and resolves itself within a few days. In other instances, newborns’ red blood cells may have been destroyed because of blood typing incompatibilities. In adults or older children, bilirubin is measured to diagnose and/or monitor liver diseases (such as cirrhosis, hepatitis, or gallstones).

Newborns: Excessive bilirubin damages developing brain cells in infants and may cause mental retardation, physical abnormalities, or blindness. It is important that bilirubin in newborns does not get too high. When the level of bilirubin is above a critical threshold, special treatment is used to reduce it. An excessive bilirubin level may result from the breakdown of red blood cells (RBCs) due to Rhesus blood typing incompatibility. (if the mother is Rhesus negative [Rh-], the father is Rhesus positive

 [Rh+], and the fetus is Rh+, then the mother develops antibodies against the newborn baby's RBCs, which are destroyed.)

Adults and children: Doctors may request bilirubin tests (along with other tests, especially when jaundice is present) to find out if liver damage exists. Bilirubin levels can be used to monitor the progression of jaundice and to discover if it is the result of red blood cell breakdown or liver disease. This investigation can be done by measuring two different chemical forms of bilirubin—direct (or conjugated) and indirect (or unconjugated) bilirubin. If the direct bilirubin is high there may be some kind of blockage of the liver or bile duct, perhaps due to gallstones, hepatitis, trauma, a drug reaction, or long-term alcohol abuse. If the indirect bilirubin is increased, haemolysis (undesirable breakdown of red blood cells) may be the cause.

Although bilirubin may be toxic to brain development in newborns (up to the age of about 2–4 weeks), high bilirubin in older children and adults does not pose the same threat. In older children and adults, the 'blood-brain barrier' is more developed and prevents bilirubin from crossing this barrier to the brain cells. High bilirubin levels in children or adults, however, strongly suggest a medical condition that must be investigated and treated.

Jaundice results from high levels of bilirubin. Increases in bilirubin may be due to metabolic problems, obstruction of the bile duct, physical or chemical damage to the liver (cirrhosis), or an inherited abnormality (Gilbert’s, Rotor’s, Dubin-Johnson, or Crigler-Najjar syndromes).