Bilirubin

What is being analysed?
Bilirubin is an orange-yellow pigment found in bile. Red blood cells (RBCs) normally break down 120 days after entering the circulation. At that point, a component of RBCs, haemoglobin (the red pigment in RBCs that carries oxygen to the tissues), is broken down into bilirubin. About 250-350 mg of bilirubin is formed every day in a healthy adult; 85% of it comes from red blood cells that die because they are old or damaged, and the rest comes from the bone marrow and liver.

Unconjugated bilirubin is carried to the liver, which attaches sugars to it, producing conjugated bilirubin. The liver releases conjugated bilirubin into the bile; in the small intestine conjugated bilirubin is further broken down by the resident bacteria. Some of the bile is stored in the gallbladder. As bilirubin in the blood rises, the skin takes on a more intense yellowish colour.
Normally, most bilirubin circulates in the blood in unconjugated form.

How is the sample collected for testing?
In newborn babies blood is often collected from the heel, using a small sharp lancet to prick the skin of the heel so that a few drops of blood can be collected in a small tube. In adults a standard blood sample is taken from a vein.
Non-invasive technologies that measure bilirubin directly through the skin (transcutaneous bilirubinometer) are also available.

How is it used?
When is it requested?
What does the test result mean?
Is there anything else I should know?

How is it used?
When bilirubin levels are high, a condition called jaundice develops and further tests are needed to find the cause. Too much bilirubin may mean that too much is being produced because of haemolysis (increased destruction of red blood cells), or that the liver can no longer remove bilirubin properly (because of blocked bile ducts or other liver diseases such as hepatitis or cirrhosis, or because of inherited disorders of bilirubin metabolism).

Raised bilirubin is commonly seen in newborn babies between the first and third days of life: this is physiological jaundice of the newborn. In the first 24 hours of life, up to 50% of full-term babies, and an even higher percentage of premature babies, may have high bilirubin levels. This happens because at birth the liver is not fully mature and cannot metabolise bilirubin properly. The condition resolves within a few days. In other cases neonatal jaundice is due to excessive destruction of red blood cells because of incompatibility between the baby’s blood and the mother’s (haemolytic disease of the newborn).

In adults, as in children, bilirubin is measured to diagnose and/or monitor liver diseases such as cirrhosis, hepatitis or gallstones. Patients with sickle cell anaemia or haemolytic anaemia from other causes may have episodes of excessive red blood cell destruction, which raises blood bilirubin levels.

When is it requested?
The doctor usually requests the bilirubin test together with other tests (alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase) in patients with symptoms of impaired liver function. Bilirubin is measured in patients who have jaundice (yellow eyes or skin), a history of heavy drinking, suspected drug use, or exposure to hepatitis viruses. Other symptoms may include dark or wine-coloured urine, nausea/vomiting, and a painful or swollen abdomen. Tiredness and general malaise can accompany liver disease. Measuring bilirubin in newborn babies is considered standard care.

What does the test result mean?
Newborn babies: excess bilirubin can destroy developing nerve cells, leading to learning disability, physical abnormalities or blindness. It is important that bilirubin in newborn babies does not become too high. When this is about to happen, appropriate treatment must be started to lower it. This can happen because of Rh incompatibility (the mother is Rh negative, the father and baby Rh positive): the mother develops antibodies against the baby’s red blood cells, some of which are then destroyed.

Adults and children: high bilirubin levels can indicate liver damage or disease, and bilirubin is used to monitor the course of jaundice. If conjugated bilirubin is raised, there may be blocked bile ducts, hepatitis, liver injury, a reaction to medicines or long-term alcohol abuse. Inherited disorders caused by abnormal bilirubin metabolism (Gilbert’s, Rotor, Dubin-Johnson and Crigler-Najjar syndromes) can keep it permanently raised.

1. Are some people at higher genetic risk of high bilirubin levels (hyperbilirubinaemia)?
2. How are high bilirubin levels and/or jaundice treated?
3. Is there anything I can do to keep my bilirubin levels normal?

1. Are some people at higher genetic risk of high bilirubin levels (hyperbilirubinaemia)?
There are several inherited conditions: Gilbert’s, Rotor, Dubin-Johnson and Crigler-Najjar syndromes. Of these four, Crigler-Najjar syndrome is the most severe and can be fatal. The first three, although chronic, do not usually cause significant problems, although they can get worse in certain circumstances.

2. How are high bilirubin levels and/or jaundice treated?
Treatment depends on the cause of the jaundice. In newborn babies, phototherapy (special light therapy), exchange transfusion in severe cases and some medicines lower bilirubin levels. Gilbert’s, Rotor and Dubin-Johnson syndromes do not usually need any treatment. Crigler-Najjar syndrome can be helped by some medicines, but if these do not work a liver transplant may be considered.
Jaundice due to blocked bile ducts can often be treated with surgery to clear the blockage. Jaundice due to cirrhosis, often caused by long-term alcohol abuse, may not respond to any treatment, although stopping drinking and eating well can improve the situation, provided the liver damage has not gone beyond what the body can tolerate.

3. Is there anything I can do to keep my bilirubin levels normal?
There is no specific remedy, but it is well known that long-term excessive drinking can lead to cirrhosis and permanent liver damage. Avoiding long-term excessive drinking and eating properly can keep the liver healthy. Blockages of bile flow due to gallstones, pancreatic cancer or pancreatic cysts may require surgery.