What is bilirubin

When we check liver function or jaundice, we often refer to the bilirubin value and analyze it based on the conclusion. However, for ordinary people, the meaning of various professional terms may not be understood, and bilirubin is one of them. When a child develops jaundice, he or she will definitely want to understand the situation in detail. So, what is bilirubin? Let’s take a closer look below.

Bilirubin is a type of bile pigment and the main pigment in human bile. It is orange-yellow in color. Bilirubin is the main metabolite of iron porphyrin compounds in the body. It is toxic and can cause irreversible damage to the brain and nervous system, but it also has antioxidant function and can inhibit the oxidation of linoleic acid and phospholipids. Bilirubin is an important basis for clinical diagnosis of jaundice and an important indicator of liver function.

Classification

Total bilirubin: High indirect bilirubin and high direct bilirubin indicate hepatocellular jaundice, liver cell damage, decreased liver function, and the liver cannot completely convert indirect bilirubin into direct bilirubin. At the same time, compression of the intrahepatic bile duct causes excretion disorders, and direct bilirubin cannot be completely discharged into the bile duct. It may be accompanied by acute icteric hepatitis, chronic active hepatitis, cirrhosis, liver cancer and other diseases.

Direct bilirubin: indicates obstructive jaundice.

Indirect bilirubin: It may be caused by hemolytic jaundice. Elevated direct bilirubin may also be caused by blood type incompatibility during blood transfusion, anemia, etc.

In liver function tests, the normal range of bilirubin is as follows:

[Total bilirubin] 1.71～21μmol/L (0.1mg/dl～1.0mg/dl)

[Direct bilirubin] 0～7.32μmol/L (0～0.2mg/dl)

[Indirect bilirubin 0～13.68μmol/L (0～0.8mg/dl)

Compounds containing porphyrin in the body include hemoglobin, myoglobin, peroxidase, catalase and cytochrome. Adults produce about 250 to 350 mg of bilirubin per day. The main sources of bilirubin are: ① 80% to 85% of bilirubin comes from the disintegration of aging red blood cells. ② About 15% is formed by the destruction of immature red blood cells in the bone marrow during the hematopoiesis process (ineffective erythropoiesis in the bone marrow). ③A small amount comes from the destruction and decomposition of hemoglobin-containing proteins (hemoprotein), such as myoglobin, peroxidase, cytochrome, etc. Some people call this bilirubin that is not produced by the decomposition of aging red blood cells "bypass bilirubin."