When taking a biochemical blood test, you can see the line "conjugated bilirubin". There are norms 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 breakdown of hemoglobin, myoglobin and cytochrome proteins. The substance is divided into conjugated bilirubin, which is called direct, and unconjugated bilirubin. The decay products enter the bile and are excreted from the body.
In a he althy 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 based on the results of the tests. For accurate diagnosis, bilirubin is indicated in the analyzesconjugated and unconjugated.
The structure of bilirubin
By chemical properties, two forms of a substance are distinguished:
- unconjugated formed in the form of various structures;
- conjugated appears after bonding with glucuronic acid.
Bilirubin is able to bind to one or two acid molecules. A sharp increase in bilirubin occurs with hemolysis - the destruction of red blood cells.
The structure of conjugated bilirubin resembles a crystal that is difficult to dissolve in water. Tissue macrophages are used to transport heme to bilirubin. Every day, aged red blood cells are destroyed in a person, up to 8 g of hemoglobin is released, which turns into 350 mcg of bilirubin.
How is bilirubin formed in the body?
During the day, 9 heme-containing proteins break down in humans. Most of it belongs to the hemoglobin of erythrocytes. Erythrocytes 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, the protein part and bilirubin are split off.
The formed bilirubin goes back into the blood and binds to metals and amino acids, which do not allow the substance to leave the body with urine. This type is called unconjugated or indirect bilirubin.
Albumin joins bilirubin, which carries the substance to the bile ducts and intestines. In some casesduring transfer, part of the bilirubin enters the bloodstream.
In the liver, hepatocyte cells capture bilirubin and cleave it from albumin. Conjugated bilirubin is produced by the enzyme UDPHT (glucuronyl transferase).
Excess bilirubin can disrupt cell function. Nerve cells are the most sensitive to it. Normal blood contains 80% indirect and 20% direct bilirubin.
Features of bilirubin, called conjugated
Direct bilirubin got its name for the property to give a direct reaction with the reagent used in the analysis. The mechanism of formation of conjugated bilirubin occurs in the liver. Most of it is excreted through the intestines, a small amount is excreted through the kidneys with urine in the form of urobinogen.
A feature of direct bilirubin is its minimal toxicity, unlike indirect. A distinctive feature of direct bilirubin is the possibility of excretion from the body due to solubility. The formation of conjugated bilirubin occurs on the basis of unconjugated.
Indirect bilirubin is practically insoluble in water. it requires fats, for this reason the accumulation occurs in adipose tissues and brain lipids. Indirect bilirubin is excreted only after conversion to conjugated.
The liver is involved in the production of 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 transformation 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 due to the insolubility of bilirubin, it cannot be removed without transformation. The insoluble substance must pass into conjugated bilirubin.
Once in the bile ducts, soluble bilirubin is excreted into the intestine, where further conversion takes place. Part of the intermediate compounds is absorbed back into the blood. In order not to harm the body, the liver again catches the "fugitives" and transfers them to direct bilirubin, and then to the intestines.
Bilirubin norms
To understand how dangerous elevated 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 the bilirubin levels are checked. Total bilirubin includes conjugated and unconjugated. At birth, the general indicator is 51-60 µmol / l. On the second day, it increases and can reach up to 170-200 µmol/l. Gradually, total bilirubin returns to normal and by the end of the first month it decreases to general values. Children over 1 month old and adults should have a value of 8.5-20.5 µmol/L.
Unconjugated bilirubinconsists of up to 75% of the total and is not more than 15.4 µmol / l. During the peak period, the percentage changes to 90%.
Conjugated bilirubin is normally up to 5.1 µmol/L in the blood. This is 25% of the total, at the peak of at least 10%.
High levels of bilirubin in newborns are called "physiological jaundice". It is caused by a special type of hemoglobin that an adult does not have. Additional excretion is due to the immaturity of the liver and enzymes that convert bilirubin into soluble.
Diagnostics and tests
Deciphering blood tests is important for making a diagnosis. Changes in bilirubin are detected by a biochemical blood test.
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 the conjugated bilirubin is increased more than 2 times, then there is probably a violation of the production of bile, direct bilirubin ceased to be excreted in full. To exclude an error, 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:
- Elevated unconjugated bilirubin outside of treatment. A large amount of bilirubin is created, which a he althy liver cannot handle.
- Elevated conjugated bilirubin outside the liver. Most likely, the outflow of bile is disturbed.
- Hepatic unconjugated bilirubin increased. There's a reason the liver can't convert bilirubin.
- Increased direct liver-type bilirubin. There was a violation of the outflow of bile.
Symptoms of elevated 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, bad breath;
- presence of a gray coating on the tongue;
- pain in the right hypochondrium;
- heaviness after eating fatty foods;
- stool disorder;
- yellow skin and mucous membranes;
- piss the color of beer;
- light feces;
- dizziness;
- itch.
Temperatures may rise in some cases.
Reasons for an increase in an adult
Given that total bilirubin and conjugated bilirubin are elevated, the following types of jaundice are distinguished:
- parenchymal;
- mechanical;
- hemolytic;
- mixed.
Increase in total bilirubin occurs due to various physical and psychological factors. The boundaries of the total amount of bilirubin, even in a he althy person, are mobile. There are factors that influence the increase in total bilirubin:
- physical activity;
- overeating;
- long-term diets.
An increase in total bilirubin indicates liver damage. Most often, the skin turns yellow. These symptoms occur with the following diseases:
- hepatitis;
- hepatosis;
- cirrhosis of the liver;
- liver tumors;
- alcohol abuse.
In 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;
- gall bladder spasms;
- violation of the bubble structure;
- cholangitis;
- helminthiases;
- bile duct disorder;
- bladder injury;
- complications after surgery;
- gall bladder tumor.
If conjugated bilirubin is normal, and unconjugated bilirubin is elevated, then this indicates a rapid breakdown of red blood cells. This condition is typical for newborns. In adults, it occurs due to trauma. Problems arise in the work of 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;
- transfusion of incompatible blood type;
- Rhesus conflict during pregnancy;
- taking hormonal drugs;
- hereditary diseases;
- typhoid.
Causes of an increase in newborns
Whenan increase in bilirubin on the 3rd day by more than 200 μmol / l, neonatologists take measures to reduce it. An increase in this indicator can adversely affect the condition of the baby. At the same time, conjugated bilirubin almost does not grow, and the total amount reaches 300-400 µmol/L.
The causes of neonatal jaundice are:
- difficult pregnancy;
- gestational diabetes mellitus;
- difficult birth;
- hypoxia during childbirth.
A reading over 300 has a negative effect on the baby's nervous system and can indicate hormonal disorders, liver problems, bowel obstruction, or a genetic disease.
For treatment, it is necessary to find out the true cause. The child is given phototherapy, if necessary, put droppers. Prolonged jaundice, if left untreated, causes developmental delays.
Increased bilirubin in pregnant women
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 performance.
Pregnant women develop hyperbilirubinemia for the following reasons:
- severe toxicosis in the early stages;
- eclampsia;
- fatty liver developing during pregnancy;
- gallstone disease;
- pregnancy cholestasis.
With cholestasis of pregnancy, all symptoms disappear after birthbaby.
Decrease in bilirubin
Decrease in bilirubin is less common than an increase. If the indicators of direct bilirubin change downwards, it is necessary to find out the reason.
The reasons for the decrease in direct bilirubin are:
- alcohol abuse;
- taking hormonal drugs;
- long-term antibiotic treatment;
- excess of ascorbic acid.
Decrease in indirect bilirubin occurs when:
- pregnancy;
- in the neonatal period.
Decrease in unconjugated bilirubin may indicate kidney failure. An increase in the load on the kidneys, an increase in blood pressure reduces indirect bilirubin.
