Unconjugated bilirubin

Unconjugated bilirubin is a form of bilirubin that has not yet undergone a process known as conjugation. It is one of the two main types of bilirubin, the other being conjugated bilirubin. Unconjugated bilirubin is also known as indirect bilirubin.

Overview

Unconjugated bilirubin is produced as a byproduct of the breakdown of heme, a component of hemoglobin found in red blood cells. This process occurs in the reticuloendothelial system, primarily in the spleen. The unconjugated bilirubin is then transported to the liver, where it is converted into conjugated bilirubin.

Clinical significance

High levels of unconjugated bilirubin in the blood can lead to a condition known as jaundice, which is characterized by a yellowing of the skin and eyes. This can occur as a result of excessive hemolysis (breakdown of red blood cells), impaired uptake of bilirubin by the liver, or a defect in the conjugation process.

In newborns, high levels of unconjugated bilirubin can lead to a potentially serious condition known as neonatal jaundice. If left untreated, this can progress to kernicterus, a form of brain damage caused by the deposition of bilirubin in the brain tissues.

Measurement

Unconjugated bilirubin can be measured as part of a liver function test. This involves a blood test that measures the total bilirubin level, which includes both unconjugated and conjugated bilirubin. The level of unconjugated bilirubin can then be calculated by subtracting the level of conjugated bilirubin from the total bilirubin level.

See also

• Bilirubin metabolism
• Gilbert's syndrome
• Crigler-Najjar syndrome
• Dubin-Johnson syndrome

Unconjugated bilirubin Resources
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