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Bilirubin (bilirubin value)

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Written by Lydia Kloeckner • Medical editor

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When red blood cells break down, bilirubin is formed. It can be detected in both blood and urine. In certain illnesses, increased amounts of bilirubin enter the blood. Some conditions also cause the amount of bilirubin in the urine to increase. Here you can find out what exactly the bilirubin values ​​say, which values ​​are normal and why many newborn babies have high bilirubin values.

Bilirubin is an orange substance that is produced when old red blood cells are broken down. Red blood cells are responsible for distributing oxygen throughout the body. They only live about 120 days. Then the body breaks them down. But it keeps producing new blood cells to replace the old ones.

Most of the breakdown of red blood cells takes place in the spleen. There so-called phagocytes break down the red blood cells into their individual parts. The red blood pigment hemoglobin is an important component of the red blood cells. Oxygen is bound to hemoglobin during transport through the body. Hemoglobin owes its red color to one of its building blocks, the so-called heme. When the red blood cells break down, the phagocytes also break down the heme. Bilirubin is one of the breakdown products.

The body cannot immediately excrete bilirubin in the urine because bilirubin does not dissolve in water. This is why bilirubin is first transported to the liver via the blood, where it is chemically modified so that it dissolves in water. In this water-soluble form, it can leave the body in a number of ways:

  • A small amount of the bilirubin produced in the liver is transported directly to the kidneys via the blood. These then excrete it with the urine.

  • Most of the bilirubin enters the intestine with the bile. Intestinal bacteria break it down further. This creates the so-called urobilinogen. Most of the urobilinogen is excreted in the stool. A smaller proportion is absorbed into the blood through the intestinal wall. On the one hand, the blood conducts the urobilinogen to the liver, from where it is returned to the intestine. On the other hand, the blood transports a very small amount of urobilinogen to the kidneys, which excrete it in the urine.

Certain diseases can lead to increased levels of bilirubin in the blood. The excess bilirubin is eventually deposited in the tissue. This causes the skin, mucous membrane and dermis of the eye to turn yellow. One then speaks of jaundice.

Various tests are necessary to determine the cause of jaundice. The blood values ​​and a urine test provide the first clues. In some diseases that are associated with jaundice, only the bilirubin levels in the blood are increased. Some of these diseases - but not all - also increase the amount of bilirubin in the urine.

The urine test alone is therefore only of limited informative value. However, the overall picture that emerges from the results of both examinations is revealing: If only the blood values ​​are increased, but not the urine values, certain diseases can be ruled out, for example.

Bilirubin in the urine

Certain diseases of the liver or biliary tract cause the amount of bilirubin in the urine to increase. Because when the liver can no longer excrete bilirubin unhindered via the biliary tract, it instead releases more of it into the blood. Bilirubin then reaches the kidneys via the blood, which then excretes it in the urine. In this case one speaks of bilirubinuria.

The cause is usually a disease in which the liver is impaired or the biliary tract is blocked, for example:

If a patient has symptoms that suggest they have this condition, the doctor may do a urine test first. He or she usually uses a test strip that measures various substances in the urine.

The test strip is dipped into the urine sample. If the bilirubin concentration in the sample exceeds a certain value, a field on the strip changes color. This means: the person affected has bilirubinuria.

In addition to bilirubin, the test strip measures another substance: urobilinogen. This occurs when bilirubin is broken down in the intestine. The combination of both test results can provide initial indications as to which illness is behind the patient's complaints:

  • If the urine contains increased amounts of both substances, liver damage may be the cause (e.g. liver failure due to hepatitis). The weakened liver cells then release less bilirubin into the biliary tract, because this elimination route costs them energy. Instead, more bilirubin gets into the bloodstream. At the same time, the urobilinogen present in the blood can no longer leave the body via the damaged liver. Thus both substances "accumulate" in the blood. The blood transports them to the kidneys, which they excrete with the urine.

  • If the bilirubin is very high and the amount of urobilinogen normal, the biliary tract may be blocked - for example by gallstones. The liver cells then release bilirubin to the bile. However, this cannot flow away unhindered. This is why most of the bilirubin produced in the liver ends up in the blood (and thus in the urine). However, hardly any bilirubin ends up in the intestines. The intestinal bacteria also break down less of it, so that less urobilinogen is formed. (However, the test strip only shows increased values; decreased values ​​cannot be determined with it.)

  • If only the amount of urobilinogen in the urine is increased, there is probably no disease of the liver or biliary tract behind it. An increase in urobilinogen suggests a disease in which more red blood cells are destroyed. Because when they are broken down, bilirubin is produced, which in turn is broken down into urobilinogen.

Important: The bilirubin that can be measured in the urine is always so-called direct bilirubin, which is water-soluble. It is produced in the liver from the water-insoluble form, the so-called indirect bilirubin. The insoluble bilirubin cannot be detected in the urine, only in the blood.

Bilirubin direct and total

The water-soluble form of bilirubin is called direct bilirubin. When red blood cells are broken down in the spleen, bilirubin is first produced, which does not dissolve in water. It's called indirect bilirubin. In order to be able to excrete it with the bile and urine, the body must first make it water-soluble.

The chemical remodeling is the job of the liver. The liver takes indirect bilirubin from the blood and converts it to direct bilirubin. The direct bilirubin is then mainly released into the intestine via the bile. A small proportion gets into the blood. Blood therefore contains both direct and indirect bilirubin. Both together make up the total bilirubin.

The blood test usually determines total bilirubin and direct bilirubin. The proportion of indirect bilirubin can be calculated from the difference. The following table shows which standard values ​​apply to the two forms:

AgeTotal bilirubinBilirubin directly
Newborns up to the 5th day<13.5 milligrams per deciliter (mg / dl)<0.3 mg / dl
Adults<1.1 mg / dl<0.3 mg / dl

Bilirubin increased: what does it mean if the value is too high?

There can be various reasons for increased bilirubin levels in the blood. The most common causes include:

In order to determine the cause of the increase, the doctor must also take into account the other blood values ​​and pay attention to which proportion of the bilirubin is increased.

Indirect bilirubin too high, direct bilirubin normal

If the amount of indirect bilirubin in the blood is slightly increased, Meulengracht's disease may be behind it. This is a hereditary disorder of the bilirubin metabolism. Those affected have problems converting indirect bilirubin to direct bilirubin. The enzyme responsible for this does not work properly with them. As a result, the amount of indirect bilirubin remains slightly increased over the long term, but this usually does not lead to symptoms. Only about 3 to 10 out of 100 people will develop jaundice.

A greatly increased level of indirect bilirubin in the blood can be an indication of haemolytic anemia. This is a form of anemia in which more red blood cells die. Since bilirubin is produced when red blood cells break down, more bilirubin gets into the blood in this form of anemia. This is bilirubin that is insoluble in water, also known as indirect bilirubin.

In contrast, the level of direct (water-soluble) bilirubin in the blood does not increase. This is because the liver can only make a limited amount of bilirubin soluble in water, i.e. convert it into direct bilirubin. In hemolytic anemia, there is so much additional bilirubin that the liver cannot keep up.

Increased proportion of direct bilirubin

This suggests a problem with the excretion of bilirubin via the liver. Gallstones may block the biliary tract, preventing the bile from draining properly. The liver can then still absorb indirect bilirubin from the blood and convert it into direct bilirubin - that is why the proportion of indirect bilirubin in the blood does not increase. However, the direct bilirubin cannot be excreted with the bile, so that more of it gets into the blood.

Both bilirubin levels increased

In this case, the liver no longer seems to be working properly - due to inflammation (hepatitis) or a tumor, for example. The impaired liver can only convert a small part of the indirect bilirubin into direct bilirubin. At the same time, it no longer manages to transport the direct bilirubin into the biliary tract. Therefore, both forms of bilirubin rise in the blood.

Lower elevated bilirubin levels

In order to reduce elevated bilirubin levels, the underlying disease must be treated. Which means or measures are necessary for this depends on the disease. Liver inflammation caused by viruses (hepatitis B) can be treated with antiviral drugs, for example. If gallstones were the reason for the increased bilirubin levels, the doctor can remove them. The bilirubin level in the blood then falls back to a normal level.

Bilirubin in the newborn baby

Many babies have elevated bilirubin levels shortly after they are born. In around every second newborn, so much bilirubin is deposited in the skin that it turns yellow. One then speaks of neonatal jaundice (icterus neonatorum).

The excess bilirubin is created because babies are born with large numbers of red blood cells that have a short lifespan. Your body therefore has to "dispose of" many red blood cells shortly after birth, with an increase in bilirubin. However, the liver is not yet able to break it down quickly enough. This is why bilirubin accumulates in the blood and in the skin.

Newborn jaundice is usually not dangerous. As a rule, the bilirubin level normalizes after one to two weeks at the latest - even without therapy. Treatment is only necessary if the bilirubin level is very high, because above a certain amount the bilirubin can cause damage to the body (including the brain).

To prevent this, the child usually receives light therapy: their skin is repeatedly irradiated with blue light for a few hours. The light sets in motion a chemical reaction in which the indirect bilirubin deposited in the skin is converted into direct bilirubin. In this form, the body can excrete it, so that the bilirubin level drops.

Bilirubin breakdown

Bilirubin is produced when red blood cells break down in the spleen. It then first reaches the liver. There it is chemically modified so that it dissolves in water. Most of the now water-soluble bilirubin is released by the liver with the bile to the intestine.

In the gut, bacteria continue to break down bilirubin into a substance called urobilinogen. Much of the urobilinogen is converted to stercobilin and excreted in the stool. Stercobilin is brown and gives the chair its typical color.

Online information from the anvil: www.amboss.com (accessed on: May 19, 2020)

Online information from Deximed: www.deximed.de (access date: 19.5.2020)

Online information from the Pschyrembel: www.pschyrembel.de (accessed on: May 19, 2020)

Online information from the Austrian public health portal: www.gesundheit.gv.at (accessed on: May 19, 2020)

Genzel-Boroviczény, O., et al .: Checklist for neonatology. Thieme, Stuttgart 2018

Guidelines of the Society for Neonatology and Pediatric Intensive Care Medicine (GNPI): Hyperbilirubinemia of the newborn - diagnosis and therapy. AWMF guidelines register No. 024/007 (as of August 2015)

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Last content check:19.05.2020
Last change: 22.09.2020