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Creatinine

Definition

Creatinine is the presence of creatinine in the blood.

Creatinine (not to be confused with creatine) is a substance containing nitrogen that comes from the degradation of creatine (a component of muscle tissue). It is produced by the muscles.

Normally, creatinine should be eliminated by the kidneys (see video) in urine. As soon as its rate increases abnormally in the blood, it means that renal function (filtration of the kidneys) is no longer sufficient. Creatinine itself has no interest in the organization. Nevertheless it is an interesting witness of kidney function. Indeed, its concentration inside the plasma, that is to say, the liquid part of blood (remove red blood cells, platelets and white), increases in cases of renal function loss. Its concentration decreases, in contrast, if the muscles decrease as the muscles produce creatinine is what is happening, among others, in the elderly.

His blood levels should not exceed 115 micromoles per liter, or 7 to 13 mg.

The clearance (percent removal) creatinine deteriorated progressively until the patient is in renal failure (kidneys no longer play their normal role of filtration).

The creatinine clearance reflects the possibilities and capabilities possessed by the kidneys filtering to filter a certain amount of blood, and dispose of creatine in it, in a given individual. It depends on several factors including age, amount of water drunk, health, and especially the purification capacity of the nephrons and more specifically the kidney glomerulus, which is part of the nephron used by the kidney to perform the blood filtration.

The clearance of blood can also be measured by considering a substance other than creatinine, but the use of creatine is convenient, since it exists naturally in the blood.

Creatine is a substance containing nitrogen in the body and plays a role in muscle contraction. Creatinine, present in most tissues, is synthesized from amino acids and then transformed into muscle tissue with creatine kinase.

The creatine kinase is an enzyme found mainly in muscles, which occurs in the setting aside of energy through a process called phosphorylation of creatine. Phosphorylation of creatine is also called creatine phosphokinase or (KPC).

The body (especially muscle) requires energy reserves. For this he uses creatine when the muscle is at rest. Through creatine kinase, which brings to creatine phosphoric acid itself from a substance called adenosine triphosphate, it is possible to obtain a substance called creatine phosphate or phosphagen is an energy reserve in the medium term. If necessary, the agency will be able to draw on those reserves, and a reverse reaction to that which we have just seen will get underway from creatine phosphate to replenish adenosine triphosphate, which is a source of energy immediately available for muscular activity.

In cases of muscle destruction, we find creatine kinase in the blood.

Normally, the blood level of this enzyme is less than about 200 international units per liter. This amount increases in cases of infarction but also in myopathies (muscle disease).

Forms more or less complex will allow obtaining a measure of glomerular filtration rate of GFR also called from plasma creatinine.

The formula used in humans to determine plasma creatinine is:

140-age X weight in kilograms x 1.23 ÷ Plasma creatinine (in micromoles per liter)

For women it is necessary to replace 1.23 by 1.04

The glomerular filtration rate is the criterion of kidney function. Usually it is around 120 ml per minute.

It is possible to define 70 milliliters per minute as the lower limit of normal: below this standard there renal failure becomes severe then moderate.

Starting at 10 milliliters per minute a hemodialysis is necessarily mandatory.

The plasma creatinine determination is subject to several sources of error. First use of drugs such as anticonvulsants for the control against seizures and convulsions as well as antibiotics alters the results. Intense muscular effort preceding the blood collection and supply also extremely rich in meat.

In summary only the upper limits of creatinine levels should be:

Humans 124 micromoles per liter or 14 mg per liter.

In women 97 or 11 mg seemed micromoles per liter.

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