Bilirubin is a reddish-yellow pigment found in bile that is responsible for the distinctive yellow color that tints the skin and eyes of patients with jaundice. It also turns up around bruises, creating the distinctive yellowish shade often associated with a healing bruise. Levels of this pigment can be assessed with a blood test, and they may be checked as part of a workup if a medical professional suspects that a patient is having a problem processing or eliminating it.
This pigment is produced during the breakdown of heme, a component of red blood cells. Initially, the compound is in a state known as “unconjugated” or “indirect.” The unconjugated form of the compound is not water soluble, and it binds to albumin so that it can travel through the body to the liver, where it is treated with an enzyme that turns it into conjugated or direct bilirubin. In this water soluble phase, the pigment moves into the bile.
The body normally expresses bilirubin through the urine and stool, keeping levels in the body relatively stable. If the body cannot process the compound, however, the unconjugated form can start to build up. This situation can be very serious for newborns, as the pigment can damage developing brain cells, leading to neurological problems. Buildups can also result in the development of jaundice.
A number of problems can interfere with the processing of the pigment. The body may lack enzymes that are used to create the conjugated form, allowing unconjugated levels to increase. Damage or disease in the liver can also interfere with the liver's ability to process the pigment; the impaired organ may not be able to work quickly enough to keep up with the body's production of the compound. There can also be problems with the expression of bilirubin, allowing levels of conjugated pigment to build up.
A blood test will provide information about levels of direct and indirect forms in the body. The test usually provides a normal range for reference, and levels of other compounds in the blood may be examined as well. Depending on which type is elevated and the level of elevation, a healthcare professional can start to explore the causes for a patient's malaise, and develop treatment options. If levels are dangerously high, emergency treatment may be used to remove excess pigment in the blood and bring the body back to a more normal level, with the medical professional then developing a treatment plan to avoid a recurrence of the problem.