Bilirubin. The norm of its content. Types of jaundice

All people in a certain amount of bilirubin in the blood. Its rate should not be more than 17.1 μmol / l. Sometimes there are situations when bilirubin in the body is produced in a larger amount than a healthy liver can produce during normal functioning. The bilirubin content can also increase due to liver damage, which can disrupt the excretion of bilirubin. In addition, when clogging the bile ducts of the liver very slowly and in small amounts bilirubin is excreted. The norm of its content in the blood is exceeded. This condition is called hyperbilirubinemia. In this case, bilirubin in the body accumulates to a certain concentration, after which it penetrates into the tissues, giving them a yellow color. This condition is called jaundice.

In order to more fully and correctly understand why jaundice may appear, one must first understand how bilirubin is exchanged at all. Bilirubin appears from the heme, which in the body is mainly contained in the form of hemoproteins. Hemoglobin released during the breakdown of mature red blood cells is the most significant source of bilirubin (70-80%). The rest of bilirubin is approximately in equal parts formed from hemoglobin of immature erythrocytes and their precursors in the bone marrow and from such gem-containing enzymes as catalase, cytochrome, etc. At the same time 250-400 mg is the total amount in which every day is formed in the body of an adult Human bilirubin. The norm for the analysis is 0.2-1.0 mg / dl.

If bilirubin, contained in the plasma, begins to exceed the permissible threshold, then jaundice develops. This is because bilirubin, the norm of which is significantly exceeded, begins to bind to the elastic fibers of the conjunctiva and skin. Jaundice can be of three types according to the mechanism of its formation:

1. Hemolytic (or superhepatic).
2. Caused by parenchymal liver damage (hepatic cell).
3. Caused by obstruction of the biliary tract (subhepatic or mechanical).

Hemolytic jaundice is characterized by abundant formation of unconjugated bilirubin or its stagnation in the body. In plasma, total bilirubin rises due to unconjugated. There is no bilirubin in the urine at all. This is explained by the inability of unconjugated bilirubin to penetrate through the renal filter, which is not damaged. Hemolytic jaundice can be caused by hemolytic crisis, malaria, intravascular hemolysis, toxins, vitamin B12 deficiency, and transfusion of incompatible blood. The level of unconjugated bilirubin may be increased with Gilbert's syndrome. People with this syndrome almost all the time celebrate the icterus of mucous membranes and skin. The reason for this is that the liver is not capable of capturing, conjugating and isolating bilirubin into the bile capillaries.

With parenchymal jaundice, both conjugated and unconjugated bilirubin both increase. Most often, the cause of this situation can be a disturbed clearance from the blood of unconjugated bilirubin, a disturbed excretion of conjugated bilirubin from the hepatic cells into the bile capillaries, as well as the ingress of conjugated bilirubin from hepatic capillaries overflowing with bile to the blood, through damaged hepatic cells. In this case, an elevated serum bilirubin level is accompanied by an increase in urinary excretion. However, at the first stages of the development of the disease in the urine bilirubin is almost not determined, so this test can not be called an early diagnosis.

Mechanical jaundice is caused by hepatic obstruction of the biliary tract, disturbed by outflow of bile or complete closure of the biliary canal (tumor, inflammation, stone, etc.). With this kind of jaundice, the liver capillaries are stretched, because In the liver the bile accumulates, the hepatocytes begin to squeeze and pass into the blood capillaries conjugated bilirubin. His norm in the blood plasma increases, and if the permissible renal threshold is exceeded (about 30 μmol / l), bilirubin appears in the urine.