Creatinine clearance

In modern medicine, the term "clearance" is used, which denotes a quantitative measure of the speed of purification of certain biological fluids. The use of this indicator allowed to significantly expand the understanding of the pharmacokinetics and pharmacodynamics of these and other substances.

So, for example, the clearance of creatinine is determined using a diagnostic test of Reberga-Toreeva. It is worth noting that in this case it is possible to determine the rate of filtration of both endogenously synthesized substance and incoming from outside (medicinal and other agents). An evaluation is performed by calculating the intensity of filtration (in glomeruli) by the rate of release of plasma from a specific substance. Accounting is carried out for a fixed time (mostly - day).

Speaking of creatinine, it is worthwhile to pay attention to the fact that excretion of it from the body is mainly due to the filtration activity of the kidneys. On this basis, such an indicator as creatinine clearance will be significant in assessing the functioning of the glomerular filtration of the kidneys. It should be noted that this indicator characterizes not only the functional capacity of the filter system, but also some other disturbances in the work of human organs and systems. Changed downward, the clearance of creatinine may also indicate an insufficient level of blood flow in the kidneys (atherosclerosis of the vessels, and with a sharp and acute development - thromboembolism).

Normally, the decrease in kidney activity occurs after forty years. The level of decrease in glomerular filtration is 1% per year. After sixty years, the activity level decreases somewhat faster (these changes are primarily due to aging of the body). However, it should be noted that there are no manifestations of such transformations for the reason that all metabolic processes, including the synthesis of endogenous creatinine, slow down in old age.

When preparing for a sample of Reberg, it is necessary to exclude the use of certain drugs that can influence the course of the study (preparations "Cortisol", "Furosemide", "Corticotropin", "Methylprednisolone", "Thyroxin" and others).

Samples are collected for urine sampling, and a blood test for the average serum creatinine level is performed.

Among the indications for the purpose of the study: endocrine pathologies, assessment of the functional activity of the kidneys, as well as the evaluation of the effect of physical exertion.

Depending on the specific level of clearance decrease, these or other violations are determined.

  • 30 ml / min / 1.7 m2 and more - moderate renal function decline;
  • 30-15 ml / min / 1.7 m2 - the presence of renal failure (in a compensated or subcompensated degree);
  • <15 ml / min / 1.7 m2 - renal failure in the phase of decompensation.

It is important to understand that the functional capacity of the filtering system of the kidneys determines the clearance of creatinine, the norm of which, when carrying out a sample of Reberg, indicates the normal state of the kidneys.

However, some diseases do not lead to changes in this indicator (for example, chronic pyelonephritis).

The level of creatinine in the blood depends both on the activity of its endogenous synthesis, and on the rate of its excretion in the urine. It is important to understand that this indicator depends not only on the activity of the filtering system, but also on the speed and volume of reabsorption of substances during the formation of primary urine.

Thus, at present, the Reberg test (determining creatinine clearance) has found wide application in diagnostic medicine. A direct relationship between clearance and renal function provides a high diagnostic significance of the procedure.

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