Creatinine is the norm in blood and urine. Clinical significance of the sample

Creatinine - one of the indicators of biochemistry of blood and urine. In clinical biochemistry, it is determined mainly in the study of filtration and reabsorption functions of the kidneys. For a doctor, creatinine, its norm or pathological increase speaks volumes. But let's first analyze what kind of substance, and how it is formed in the body.

From the textbook on biochemistry, you can learn that creatinine is one of the so-called final products of metabolism. It is formed from the creatine protein, which serves as a source of energy for the musculature. In muscles, creatine is in the form of a compound called creatine phosphate. With muscle contraction, creatine phosphate gives its energy, and it breaks down to the final products - creatinine, water and phosphorus residues. So in the body appears creatinine. Its concentration depends on the amount of muscle mass. Because of this, in men, the creatinine of the blood, the norm of it, is always higher than that of women.

The final products of the process of protein metabolism are excreted through the kidneys with urine. In the renal glomeruli, creatinine from the blood is filtered and enters the renal tubules. With normal functioning of the kidneys, it is completely removed from the body, that is, the blood is purified from it. On this basis, one of the most important renal tests is the Reberg test. With its help, glomerular filtration is determined. And on the basis of the known glomerular filtration, the tubular reabsorption of the kidneys is calculated. But we'll talk about this later.

Creatinine, the norm of which for men is 0.044-0.106 mmol / l, and for women - 0.44-0.88 mmol / l, it increases in the first place, with kidney disease. In a number of laboratories, the results of the study are expressed in other units - in micromoles. To translate the microwaves in micromoles, the digestion of creatinine should be multiplied by 1000. For example, the norm in men is 44-106 μmol / l.

An increase in creatinine is one of the main signs of kidney failure. It is associated with the fact that in renal lesions the filtration in the renal glomeruli decreases drastically.

However, kidney pathology is not the only reason for this increase. All conditions and diseases, under which there is a rapid disintegration of creatine phosphate in the muscles, can also increase the creatinine in the blood to high digits. It can be strengthened muscular work, hyperthyroidism, food rich in proteins, dehydration, acromegaly.

In conditions accompanied by damage to the muscle tissue, creatinine also rises. For example, extensive myocardial infarction is accompanied by an increase in creatinine. Radiation sickness, burns, the syndrome of prolonged crushing also occur with its increase.

Taking some medications increases creatinine. The rate may be exceeded if the patient receives sulfonamides, barbiturates, antibiotics from the tetracycline and aminoglycoside series.

The decrease in creatinine below the norm does not have such a diagnostic value as an increase. It may be due to insufficient intake of protein foods, starvation, exhaustion. The creatinine decreases in the first third of pregnancy, with swelling, ascites. Helps reduce creatinine long-term use of corticosteroids.

If suspected of kidney failure, as already mentioned, the Rheberg test is often prescribed.

When it is carried out, creatinine is determined, the norm of which in blood with renal insufficiency can be significantly exceeded, and urine creatinine. Urine for a sample of Reberg should be collected within a day, this gives more accurate results than if it is collected in less time. It is necessary to accurately measure its volume. A small amount of urine is delivered to the laboratory from the daily volume, it is not necessary to carry it all. When collecting urine, you should avoid physical exertion and do not eat too much protein food. Blood surrenders on an empty stomach, in the morning. The daily release of creatinine with urine is normally 4.4-17.7 mmol / day.

Having determined the creatinine of blood and urine, knowing the daily amount of urine, the weight and height of the patient (the latter concerns mainly children), the laboratory technician calculates the value of glomerular filtration and then the tubular reabsorption according to a special formula. Norms for middle-aged people: glomerular filtration for men - 82-140 ml / min, for women - 81-128 ml / min. The norm of tubular reabsorption is 95-99%. If the renal function is impaired, these values decrease.