Bilirubin level tests

When bilirubin levels are high, a condition called jaundice (yellowing of the skin and the whites of the eyes) occurs, and further testing is needed to determine the cause. Too much bilirubin means that too many red cells are being destroyed, or that the liver is incapable of removing bilirubin from the blood.

It is not uncommon to see high bilirubin levels (sometimes called neonatal bilirubin) in newborn babies (typically 1–3 days old). Within the first few hours of life, up to 50% of full-term newborns, and an even greater percentage of pre-term babies, may have high a bilirubin level. At birth, the newborn lacks the intestinal bacteria that help process bilirubin. This is not abnormal and it resolves itself within a few days. In other instances, newborns’ red blood cells could 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).

This test may be done to:
* see how well liver is working
* check for blockage of bile in the bile duct, gallbladder, or liver. If the bile duct becomes blocked, or if there is blockage of bile in the gallbladder or liver, the bilirubin level rises in the blood since it is no longer released into the intestines.
* check for certain blood problems, such as some types of anemia. Blood problems may cause a high level of bilirubin because more red blood cells are breaking down than normal.

Excessive bilirubin damages developing brain cells in infants and may cause severe problems such as 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.

Doctors may request bilirubin tests (along with other tests, especially when jaundice is present) to determine if liver damage really exists. Bilirubin levels can be used to monitor the progression of jaundice and to determine if it is the result of red blood cell breakdown or liver disease. This can be done by measuring 2 different chemical forms of bilirubin—direct (or conjugated) and indirect (or unconjugated) bilirubin. If direct bilirubin is elevated there may be some kind of blockage of the liver or bile duct, perhaps gallstones, hepatitis, trauma, drug reaction or long-term alcohol abuse. If indirect bilirubin is increased, haemolysis (undesirable breakdown of red blood cells) may be 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. Elevated bilirubin levels in children or adults, however, suggest a medical condition that must be investigated and treated.