In many diseases, when it is necessary to pass a biochemical blood test, creatinine and urea can be seen among the indicators. Their values for the most part indicate the state of the kidneys in the human body.
Both indicators are products of nitrogen metabolism. Based on the results of the analyzes, in conjunction with a survey, examination, other examination methods, the doctor draws conclusions about the functional state of the kidneys.
Definition
Urea is the end product of the breakdown of protein molecules. In the liver, proteins break down first into amino acids, and then into smaller nitrogen compounds, which are toxic to the body. They must be withdrawn. For this, urea is formed by complex chemical reactions. It is removed from the body by filtering blood in the tubules of the kidneys.
Creatinine is one of the final breakdown products of creatine. It is formed in the liver and enters the muscle and other tissues, directly participating in energy metabolism. This protein undergoes some transformation and transfers energy within the cell between its structures.
Creatinine is completely excreted by the kidneys and is not absorbed back into the blood. This property has found particular application in laboratory diagnostics.
Value
Blood creatinine and urea are the main indicators of kidney health. Since the filtration process is disturbed in some pathological processes occurring in these organs, doctors can quickly suspect something is wrong with a simple analysis.
The examination to determine the concentration of these products of protein metabolism refers to screening, that is, mass. When medical examination or admission to the hospital, the analysis is assigned to everyone. This is necessary, first of all, for the early detection of kidney disease. In addition, with increased creatinine and urea, approaches to treatment will be slightly changed, medications will be selected that have the least effect on the kidneys.
Norm
In each analysis form, opposite the specific items, the so-called reference values are painted . This is the range of normal values of one or another indicator.
Shifts in the concentration of substances depend on the ratio of the processes of their formation and excretion. From external causes, the result may be affected by excessive consumption of meat, increased physical activity.
A blood test is taken from a vein in the morning on an empty stomach, after 8-14 hours of fasting. On the eve it is better to avoid stressful situations and excessive physical exertion. The latter are allowed only with the permission of the doctor and, if necessary, check the function during such loads. It is mainly used by professional athletes.
The rates of creatinine and urea in the blood can vary widely. For urea, the indicators are basically the same and equal to 2.5-8.3 mmol / L.
Creatinine has various norms in certain age categories. For newborns, values of 27-88 μmol / L are characteristic, children under one year old - 18-35, children 1-12 years old - 27-62, adolescents - 44 - 88, adult men - 62-132, women - 44-97.
Performance decline
A decrease in serum creatinine and urea, as a rule, has no diagnostic value. Extrenal causes are not affected by this change in creatinine, unlike urea. The starvation, liver failure, decreased catabolism, that is, destruction of proteins, and also increased diuresis usually lead to its reduced indices.
But more often you can see in the analysis an increase in urea and creatinine. The reason is often found in kidney disease. This will be written below.
Increased Blood Creatinine
The concentration of a substance in the blood of healthy people is usually constant and rarely depends on extrarenal causes. Reducing its content does not matter in clinical practice.
If an increase in the indicator is detected, then first of all they think about renal failure. This diagnosis is made when reaching the level of 200-500 μmol / L. However, increased creatinine and urea are among the later signs of the disease. Such values appear with the defeat of about 50% of the substance of the kidney.
Also, an increase in creatinine can be detected in diabetes mellitus, hyperthyroidism, intestinal obstruction, muscle atrophy, gigantism, acromegaly, extensive trauma and burns. Therefore, to make the correct diagnosis, a full examination is necessary.
Blood Urea Changes
Increasing the concentration of a substance is much more important. Among the reasons there are 3 groups:
- Adrenal glands are caused by increased formation of nitrogen metabolism products in the body. Such reasons include extremely high protein intake, vomiting or diarrhea, severe dehydration, severe inflammatory processes in the body, which are accompanied by increased protein breakdown.
- Kidney. In this case, as a result of the pathological process affecting the organ, the kidney substance responsible for the filtration dies. If this important function is impaired, then urea remains in the blood, and gradually its level rises. Diseases leading to this kind of consequences include glomerulonephritis, pyelonephritis, nephrosclerosis, malignant arterial hypertension, amyloidosis, polycystic kidney disease or tuberculosis. In such cases, a donor kidney and an artificial kidney apparatus, or hemodialysis in another way, can help.
- Adrenal glands, i.e. obstructing outflow. If a dangerous substance does not find a way out through the urinary tract, then it is absorbed back into the blood, increasing the concentration there. A blockage of the pelvis of the kidney and ureter or compression from the outside, for example, stones in the lumen, adenoma, and prostate cancer, lead to such an outcome.
Decryption of analyzes
Knowing the norm of urea and creatinine in blood serum, with an increase in indicators, one can judge the degree of renal failure. It is worthwhile to consider in more detail the gradation of this state.
The criteria for ARF are:
- serum creatinine level 200-55 μmol / ml;
- an increase in its level by 45 μmol / ml with the previous value below 170 μmol / ml;
- an increase of more than 2 times compared to the original.
A severe degree of acute renal failure is established when a creatinine concentration of more than 500 μmol / ml is detected. But in the practice of a doctor, results are found above 1000 μmol / ml.
If the analysis revealed an increase in urea of more than 10 mmol / l, then this always indicates damage to the kidneys, in which case renal failure is also put, and an increase in creatinine and urea always go hand in hand. At the same time, the concentration of the latter in the range of 6.5 - 10.0 mmol / l can speak of other diseases. This condition of patients in clinical practice is called uremia.
Where to go
If the attending physician ordered to take an analysis for creatinine and blood urea, then with the results the patient should go to him. If there are minor changes, most likely, they will offer to retake the analysis, since errors in the calculations are not excluded.
If the concentration is repeatedly changed or greatly increased, the doctor will refer the patient to a nephrologist, a specialist in kidney diseases. He will understand the causes of what is happening, conduct an additional examination and prescribe the necessary treatment, give recommendations.