If the biochemical analysis shows elevated bilirubin in the blood, then there may be several reasons. To understand them, it is worth considering the metabolism of this substance.
Metabolism of bilirubin
Bilirubin is a bile enzyme. It is present in the blood in two fractions: indirect (free) and direct.
Red blood cells (erythrocytes) in the process of human life constantly die and are replaced by new ones. Dead bodies release hemoglobin, which breaks down into globin chains and a heme molecule. The latter is converted by enzymes into free (indirect bilirubin). In this form, the substance is toxic, because it dissolves in fats (but not in water), easily penetrates into cells and harms their normal work. Because nature has provided a mechanism for "neutralizing" indirect bilirubin: it, connecting with albumins of blood, moves to the liver, and then under the action of enzymes it becomes water-soluble and is excreted with bile through the small intestine. This is direct bilirubin. In sum, both fractions give a common bilirubin, and if it is elevated, the causes should be sought in violation of the mechanism described above.
Why is bilirubin raised?
We give a simplified classification.
Indirect bilirubin may be increased because of:
- disorders in the hematopoietic system;
- liver diseases.
The direct fraction of the enzyme is found in the blood above the norm when:
- liver diseases;
- impassability of extrahepatic bile ducts.
Now consider each group in more detail.
High indirect bilirubin
To violations of the hemopoietic system include hemolytic anemia, in which a large number of erythrocytes is destroyed. They release a lot of hemoglobin, and accordingly this is the reason why indirect bilirubin is increased. The liver simply does not have time to cope with its transformation into a straight line (this fraction remains normal) and further excretion.
Symptoms of such anemia:
- dizziness;
- general weakness and fatigue;
- pallor;
- low hemoglobin and the number of red blood cells;
- enlarged spleen.
A similar jump in the enzyme may also be due to malaria and sepsis.
Among the hepatic diseases, because of which the level of indirect bilirubin is high, include:
- Gilbert's syndrome ;
- the Kriegler-Nayyar syndrome;
- Lucy-Driskol syndrome;
- acquired non-hemolytic jaundice.
Such disorders are rare.
High direct bilirubin
In liver diseases, outflow of bile may be disturbed, because of which the bilirubin contained in it is not completely excreted into the small intestine, but is thrown into the blood. This occurs with hepatitis virus, bacterial, toxic and autoimmune nature.
Other causes of elevated direct bilirubin in the blood:
- intrahepatic cholestasis;
- primary biliary cirrhosis;
- jaundice of pregnant women due to the sensitivity of some women to the high content of estrogens;
- liver tumors.
Bile leaves the liver in the duodenum through one duct, and if its lumen is closed, direct bilirubin is injected into the blood. This happens when:
- compression of the bile ducts from the outside because of chronic or acute inflammation of the pancreas (pancreatitis);
- echinococcus liver (parasite);
- diverticulum of the duodenum (congenital anomaly);
- tumors of the duodenum or pancreas;
- aneurysm of the hepatic artery;
- cholelithiasis;
- acute and chronic cholangitis ;
- tumors of the bile ducts.
Treatment of elevated bilirubin in the blood is prescribed depending on the causes that caused an increase in the concentration of this enzyme.