When passing a biochemical blood test, you can see the line "conjugated bilirubin". There are standards according to which the content of this substance in the blood is considered acceptable. With diseases, the indicators increase, and the doctor prescribes treatment. An increase in direct and indirect bilirubin indicates pathological processes that should be eliminated.
What is bilirubin?
Bilirubin is a red-yellow substance that is found in human blood and is part of bile. It is formed as a result of the splitting of hemoglobin, myoglobin and cytochrome proteins. The substance is divided into conjugated bilirubin, which is called direct, and unconjugated bilirubin. Decay products enter the bile and are excreted from the body.
In a healthy person, bilirubin is contained in the blood in a certain amount. Its increase indicates excessive destruction of red blood cells. The reason for this is determined by the doctor according to the results of the tests. For accurate diagnosis, bilirubin conjugated and unconjugated is indicated in the assays.
The structure of bilirubin
By chemical properties, two forms of substance are distinguished:
- unconjugated is formed in the form of various structures;
- conjugated appears after association with glucuronic acid.
Bilirubin is able to bind to one or two acid molecules. A sharp increase in bilirubin occurs during hemolysis - the destruction of red blood cells.
The structure of conjugated bilirubin resembles a crystal, which is difficult to dissolve in water. Tissue macrophages are used to transport the heme to bilirubin. Daily in a person, aged red blood cells are destroyed, up to 8 g of hemoglobin is released, which turns into 350 μg of bilirubin.
How is bilirubin formed in the body?
During the day, a person breaks down 9 proteins containing heme. Most of them belong to erythrocyte hemoglobin. Red blood cells live in the blood for 3-4 months and are destroyed. In this case, the released hemoglobin is transferred to the spleen, liver or bone marrow, where it is oxidized by oxygen. In the process of decay, iron, protein, and bilirubin are cleaved.
The resulting bilirubin enters the bloodstream and binds to metals and amino acids that prevent the substance from leaving the body with urine. This type is called unconjugated or indirect bilirubin.
Albumin is attached to bilirubin, which transfers the substance to the bile ducts and intestines. In some cases, during the transfer, part of the bilirubin enters the bloodstream.
In the liver, hepatocytes capture bilirubin and are cleaved from albumin. Conjugated bilirubin is formed using the enzyme UFDGT (glucuronyl transferase).
Excess bilirubin can disrupt the functioning of cells. The most sensitive to it are nerve cells. Normally, the blood contains 80% of indirect and 20% of direct bilirubin.
Features of bilirubin called conjugated
Direct bilirubin got its name for the property of giving a direct reaction with the reagent that is used in the analyzes. The mechanism of formation of conjugated bilirubin occurs in the liver. Most of it is excreted through the intestines, a small amount goes through the kidneys with urine in the form of urobinogen.
A feature of direct bilirubin is its minimal toxicity, in contrast to indirect. A distinctive feature of direct bilirubin is the ability to remove from the body due to solubility. The formation of conjugated bilirubin occurs on the basis of unconjugated.
Indirect bilirubin is practically insoluble in water. he needs fats, for this reason accumulation occurs in adipose tissues and brain lipids. Indirect bilirubin is excreted only after conversion to conjugated.
The liver produces bilirubin. But a distinctive feature of direct bilirubin is the formation in special cells - hepatocytes. Also, part of the indirect bilirubin is created outside the liver.
An increase in bilirubin does not always indicate a disease, sometimes an increase in indicators occurs with a properly functioning liver.
Ways to remove bilirubin
The breakdown of hemoglobin and its conversion into bilirubin occurs in the reticuloendothelial system. Up to 80% is produced in liver cells, the rest in the spleen, bone marrow and connective tissues.
All bilirubin formed must be excreted from the body, as it is toxic to the body. But because of the insolubility, bilirubin cannot be removed without conversion. Insoluble matter must pass into conjugated bilirubin.
Once in the bile ducts, soluble bilirubin is excreted into the intestine, where further transformation occurs. Part of the intermediates are absorbed back into the blood. In order not to harm the body, the liver again catches the “fugitives” and translates into direct bilirubin, and then into the intestines.
Bilirubin norms
To understand how dangerous increased bilirubin is in the blood, it is necessary to determine the norms of indicators that depend on the age of the patient.
At birth, a blood test is taken from the baby and bilirubin values are looked at. Total bilirubin includes conjugated and unconjugated. At birth, the total rate is 51-60 μmol / L. On the second day it increases and can reach up to 170-200 micromol / l. Gradually, total bilirubin returns to normal and by the end of the first month decreases to general values. Children older than 1 month and adults should have a value of 8.5-20.5 μmol / L.
Unconjugated bilirubin is up to 75% of the total and is not more than 15.4 μmol / L. In the peak period, the percentage ratio changes to 90%.
Conjugated bilirubin normally in the blood is up to 5.1 μmol / L. This is 25% of the total, at the peak of at least 10%.
High rates of bilirubin in newborns are called "physiological jaundice." It is caused by a special type of hemoglobin, which is not found in an adult. Additional excretion occurs due to the immaturity of the liver and enzymes that convert bilirubin to soluble.
Diagnostics and analyzes
Deciphering blood tests is important for making a diagnosis. Changes in bilirubin are detected by a biochemical blood test.
The determination of direct bilirubin is important, because this indicator is a kind of marker in the diagnosis of diseases. Comparing the results with the norm, you can see the true picture.
If conjugated bilirubin is increased by more than 2 times, then probably there was a violation of bile production, direct bilirubin ceased to be excreted in full. To rule out a mistake, the doctor, when making a diagnosis, looks at other indicators of the analysis - transaminases, phosphatases, sediment.
When diagnosing, 4 groups of elevated bilirubin are determined:
- Unconjugated bilirubin increased without treatment. A large amount of bilirubin is created, which a healthy liver can not cope with.
- Conjugated bilirubin outside the liver is elevated. Most likely, the outflow of bile is disturbed.
- Increased unconjugated hepatic bilirubin. There is a reason why the liver cannot convert bilirubin.
- Direct hepatic bilirubin increased. There was a violation of the outflow of bile.
Symptoms of increased bilirubin
With an increase in bilirubin, characteristic symptoms appear that indicate a pathological condition of the patient. Analyzes confirm the diagnosis and allow you to find the cause of the ailment. Symptoms indicating that direct conjugated bilirubin is elevated:
- frequent headaches;
- nausea, halitosis;
- the presence of a gray coating on the tongue;
- pain in the right hypochondrium;
- heaviness after eating fatty foods;
- upset stool;
- yellow skin and mucous membranes;
- beer-colored urine;
- light feces;
- dizziness;
- itching
In some cases, a fever is possible.
The reasons for the increase in an adult
Given the fact that total bilirubin and conjugated is elevated, the following types of jaundice are distinguished:
- parenchymal;
- mechanical;
- hemolytic;
- mixed.
An increase in total bilirubin occurs due to various physical and psychological factors. The boundaries of the total amount of bilirubin, even in a healthy person, are mobile. Factors that influence the increase in total bilirubin are distinguished:
- physical exercise;
- binge eating;
- long diets.
An increase in total bilirubin indicates liver damage. Most often, the skin becomes yellow. Such symptoms occur with the following diseases:
- hepatitis;
- hepatosis;
- cirrhosis of the liver;
- liver tumors;
- alcohol abuse.
With an increase in direct bilirubin, the cause is inflammation in the gallbladder or ducts. This type of jaundice is considered mechanical. Occurs in the presence of the following diseases:
- gallstones
- spasms of the gallbladder;
- violation of the structure of the bladder;
- cholangitis;
- helminthiases;
- violation of the bile ducts;
- bladder injuries;
- complications after surgery;
- gallbladder tumor.
If conjugated bilirubin is normal, and unconjugated is elevated, then this indicates a rapid breakdown of red blood cells. This condition is characteristic of newborns. In adults, it occurs due to injuries. Problems arise in the circulatory system, so jaundice is called suprahepatic. The main diseases leading to an increase in bilirubin:
- iron deficiency due to genetic factors;
- heavy metal poisoning;
- incompatible blood transfusion;
- Rhesus conflict during pregnancy;
- taking hormonal drugs;
- hereditary diseases;
- typhoid fever.
Reasons for the increase in newborns
With an increase in bilirubin on the 3rd day by more than 200 μmol / l, neonatologists take measures to reduce. An increase in this indicator can adversely affect the condition of the baby. In this case, conjugated bilirubin almost does not grow, and the total amount reaches 300-400 μmol / L.
The causes of jaundice in newborns are considered:
- severe pregnancy;
- gestational diabetes mellitus;
- difficult childbirth;
- hypoxia during childbirth.
Indicators greater than 300 have a negative effect on the baby’s nervous system and may indicate hormonal disorders, liver problems, bowel obstruction, or a genetic disease.
For treatment it is necessary to find out the true cause. The child undergoes phototherapy, if necessary, put droppers. Prolonged jaundice in the absence of treatment causes a developmental delay.
Pregnant bilirubin increase
With an increase in bilirubin in pregnant women, changes in conjugated and unconjugated bilirubin are compared. Depending on the results and general condition, women determine the reason for the increase in indicators.
In pregnant women, the development of hyperbilirubinemia occurs for the following reasons:
- severe toxicosis in the early stages;
- eclampsia;
- fatty degeneration, a liver that develops during pregnancy;
- cholelithiasis;
- pregnant cholestasis.
With pregnant cholestasis, all symptoms disappear after the birth of the baby.
Bilirubin reduction
A decrease in bilirubin occurs less frequently than an increase. When direct bilirubin is changed in a smaller direction, it is necessary to find out the cause.
The reasons for the decrease in direct bilirubin are:
- alcohol abuse
- taking hormonal drugs;
- long-term treatment with antibacterial drugs;
- excess ascorbic acid.
Indirect bilirubin decreases when:
- pregnancy
- during the neonatal period.
A decrease in unconjugated bilirubin may indicate renal failure. An increase in the load on the kidneys, an increase in blood pressure reduces indirect bilirubin.