Glomerular filtration rate calculation - online calculator and Cockcroft formula. How is glomerular filtration rate measured?

Description

Method of determination

calculation according to the formula CKD-EPI-creatinine (creatinine calibrator traceable to the IDMS method).

Material under study Serum

Determining the glomerular filtration rate is essential for diagnosis, determining the stage of the disease, assessing the prognosis, choosing treatment tactics, and deciding whether to start replacement therapy for chronic kidney disease. However, currently there is no accessible, easy-to-use and at the same time the most accurate method for assessing glomerular filtration.

Reference methods are clearance methods using the introduction of exogenous substances with the necessary ideal characteristics (removed from the blood only by glomerular filtration, without being reabsorbed or secreted in the renal tubules). These include methods for assessing filtration by the rate of excretion of inulin, 51Cr-EDTA, 125I-iothalamate, or iohexol. The wide use of such methods is limited by their complexity, high cost, and the need for intravenous administration of substances foreign to the body. The method for assessing glomerular filtration by endogenous creatinine clearance does not require intravenous administration of the test substance (see test, Reberg-Tareev test). Creatinine is formed in the muscles and excreted from the blood under normal conditions mainly by glomerular filtration, without being reabsorbed or secreted in the renal tubules.

Evaluation of filtration by the ratio of creatinine concentration in the blood and its excretion with urine, taking into account body size (normalization to the standard body surface), sex and age of the patient (separate reference values) in most situations allows us to assess changes in the filtration level with satisfactory accuracy, therefore this method has wide application.

The method gives somewhat distorted results in the later stages of renal failure, since at very high concentrations in the blood, creatinine begins to be secreted in the renal tubules. In addition, the Reberg-Tareev test is not convenient enough and is not always acceptable for the patient, since it involves the collection of urine excreted during the day. Failure to comply with the rules for collecting urine often leads to an erroneous result.

As a result of the search for more convenient methods, screening methods for calculating the glomerular filtration rate in the kidneys by the level of blood creatinine (eGFR, estimated Glomerular Filtration Rate) were developed and put into practice using formulas based only on measuring blood creatinine and knowing the sex, age and ethnicity of the patient . They were derived by statistical analysis and comparison of the results of measuring the level of creatinine and assessing the glomerular filtration rate using clearance methods in a large number of patients of different ages and gender with chronic kidney disease.

One of the most common options for calculating the glomerular filtration rate is the MDRD formula (obtained in the Modification of Diet in Renal Disease clinical study). The result of the calculation takes into account gender, age and is normalized relative to the conditional average surface of the human body of 1.73 m2, which allows it to be used for grading the level of glomerular filtration and classifying the stage of chronic kidney disease. Result<60 мл/мин/1,73 м2 интерпретируется как снижение фильтрации. Существенный недостаток формулы MDRD – неточные (заниженные) результаты на уровне истинной скорости фильтрации >60 ml/min/1.73 m2.

The CKD-EPI formula (Chronic Kidney Disease Epidemiology Collaboration), subsequently developed by the same group of researchers, improves the accuracy of calculations in the range of 60-90 ml / min / 1.73 m2 and is currently recommended for use as the most suitable for outpatient and clinical practice screening method for assessing glomerular filtration rate (KDIGO, 2013, National guidelines: chronic kidney disease, 2012). The CKD-EPI formula assumes that the method used to measure the patient's creatinine level is comparable to the method on which the formula was worked out (calibration material standardized to the reference method of isotope dilution mass spectrometry - Isotope Dilution Mass Spectrometry, IDMS).

Calculation of the glomerular filtration rate by the level of blood creatinine is focused on the conditional "average" patient and is less accurate than the assessment of glomerular filtration by clearance methods.

It is unacceptable in the following situations:

body size and muscle mass of the patient deviate sharply from the average values (bodybuilders, patients with amputation of limbs);
severe wasting and obesity (BMI<15 и >40 kg/m2);
pregnancy;
diseases of the skeletal muscles (myodystrophy);
paralysis / paresis of the limbs;
vegetarian diet;
rapid decline in kidney function (acute or rapidly progressive nephritic syndrome);
laboratory studies to resolve the issue of dosage of nephrotoxic drugs;
making a decision to start renal replacement therapy;
condition after kidney transplant.

In these cases, more accurate clearance methods for assessing the level of glomerular filtration should be resorted to.

Literature

National recommendations. Chronic kidney disease: basic principles of screening, diagnosis, prevention and treatment approaches. Clinical Nephrology No. 4, 2012, p. 4-26.
KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease/ – Kidney Int/ 2013, Vol 3 Issue 1.
Stevens L.A., Claybon M.A., Schmid C.H. et al. Evaluation of the Chronic Kidney Disease Epidemiology Collaboration equation for estimating the glomerular filtration rate in multiple ethnicities. Kidney Int. 2011; 79:555–562.

Training

It is preferable to take blood in the morning on an empty stomach, after 8-14 hours of a night fasting period (you can drink water), it is permissible in the afternoon 4 hours after a light meal. On the eve of the study, it is necessary to exclude increased psycho-emotional and physical activity (sports training), alcohol intake.

Indications for appointment

Screening evaluation of kidney function (for limitations, see Description section).

Interpretation of results

The interpretation of test results contains information for the attending physician and is not a diagnosis. The information in this section should not be used for self-diagnosis or self-treatment. An accurate diagnosis is made by the doctor, using both the results of this examination¤ and the necessary information from other sources: history, results of other examinations, etc.

Calculation formulas for patients (Caucasians), where CREAT is serum creatinine, µmol/l:

Women - if blood creatinine is less than or equal to 62 µmol/l: CKD-EPI = 144 × (0.993^YEAR) × ((CREAT/88.4)/0.7)^(−0.328))

Women - if blood creatinine is above 62 µmol/L: CKD-EPI = 144 × (0.993^YEARS) × ((CREAT/88.4)/0.7)^(−1.210))

Men - if blood creatinine is less than or equal to 80 µmol/L: CKD-EPI = 141 × (0.993^YEAR) × ((CREAT/88.4)/0.9)^(−0.412))

Men - if blood creatinine is above 80 µmol/L: CKD-EPI = 141 × (0.993^YEARS) × ((CREAT/88.4)/0.9)^(−1.210))

Note. The original CKD-EPI formula, obtained predominantly in Caucasian patients, is used. When evaluating the influence of race/ethnicity with patients from the USA, Europe, China, Japan and South Africa, the following racial/ethnic adjustment coefficients were developed: African Americans - x1.16, Asians - x1.05 (women) and x1.06 (men) , American Indians and Hispanics - x1.01 (compared to the rest of the mixed group).

The use of these four-racial-ethnic modified equations has shown satisfactory results when validated in the US, Europe, and China, but significant deviations have been identified for patients from Japan and South Africa. In Russia, at the St. Petersburg Research Institute of Nephrology, a good agreement between the results of calculations of the glomerular filtration rate CKD-EPI and the results of reference clearance methods in Caucasian patients was confirmed, the method is recommended for use in outpatient practice (the question of the effectiveness of using modified equations in heterogeneous racial and ethnic groups of the Russian population has not yet been studied).

The formula is not applicable to children.

Units: ml/min/1.73 m2.

Reference values: >60 ml/min/1.73 m2.

Result interpretation:

A result below 60 ml/min/1.73 m2 is considered abnormal. Restrictions in the application of the test - see the section "Description".

Designation	Characteristics of kidney function	GFR, ml/min/1.73 m2
C1	high and optimal	>90
C2	Slightly reduced*	60–89
C3a	Moderately reduced	45–59
C3b	Significantly reduced	30–44
C4	Dramatically reduced	15–29
C5	terminal renal failure

*relative to the level in young people

Questions
and answers

I am 40 years old, they put the VVD on the hypertensive type, BP 150/100. What tests to do to rule out hypertension?

There is a group of diseases with an increase in blood pressure. One of them is vegetovascular dystonia (VVD) of the hypertensive type, which is based on functional cardiovascular disorders caused by a disruption in the activity of the autonomic nervous system. These disruptions are usually temporary.

A persistent increase in blood pressure can be observed in hypertension or in secondary arterial hypertension. The latter most often accompany kidney disease, stenosis (narrowing) of the renal artery, primary hyperaldosteronism, pheochromocytoma, and Cushing's syndrome. Mentioned endocrine diseases are characterized by excessive production of adrenal hormones, which causes an increase in blood pressure.

To determine the causes of arterial hypertension, it is recommended:

analysis of daily urine for metanephrines and free cortisol, a blood test for aldosterone-renin ratio, cholesterol and its fractions, glucose, determination of the glomerular filtration rate of the kidneys, a general clinical analysis of blood and urine;
ECG, EchoCG, ultrasound of the vessels of the head and neck, renal vessels, kidneys and adrenal glands;
consultation of a therapist, neurologist, cardiologist and ophthalmologist (for examining the fundus).

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I need to check my kidneys. What tests can be done to judge the possibility of an inflammatory process or rule out a kidney problem?

The kidneys are a paired organ that removes end products of metabolism, toxic substances from the body, maintains electrolyte levels, acid-base balance and blood pressure.

If you suspect the development of inflammatory diseases of the kidneys, you should consult a general practitioner, urologist or nephrologist.

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In this section, you can find out how much it costs to complete this study in your city, read the description of the test and the table for interpreting the results. When choosing where to take the analysis "Globular filtration, calculation using the CKD-EPI formula - creatinine (eGFR, Estimated Glomerular Filtration Rate, CKD-EPI creatinine equation)" in Moscow and other cities of Russia, do not forget that the price of the analysis, the cost of the procedure for taking biomaterial , methods and terms of examinations in regional medical offices may differ.

Clinical significance of glomerular filtration rate

Glomerular filtration rate in nephrology is a parameter of paramount importance, since this indicator determines the functional capacity of the kidneys. Regardless of the causes of impaired renal function (its decrease), the glomerular filtration rate decreases. There is a clear correlation between the severity of kidney disease and GFR. The glomerular filtration rate begins to decrease in the very early stages of renal dysfunction (much earlier than the onset of the first symptoms of the disease). Kidney pathology can be acute (developing over several hours or days) and chronic (slowly progressing over several months or years).

Depending on the glomerular filtration rate, it is possible to determine acute and chronic kidney diseases that can go into the terminal stage (in this case, the patient's life will depend on renal replacement therapy - dialysis). In acute renal failure, the patient may be prescribed a single short-term dialysis; in chronic renal failure - lifelong dialysis or kidney transplantation.

It should be noted that at present, the theory of “acute kidney injury” dominates among specialists, which expands the possibilities of interpreting pathophysiology processes that occur when metabolic processes in the renal parenchyma are disturbed due to the action of various etiological factors (for example, with the nephrotoxic effect of xenobiotics, hemodynamic disorders, etc.). ). In some cases, such disorders cause an increase in the concentration of metabolites (urea and creatinine), which is usually considered as acute renal failure. But the introduction of more sensitive markers of damage to the structure of the kidneys makes it possible to carry out early diagnosis, thus providing effective therapy for damaged kidneys.

Studies have shown that in violation of ultrafiltration in the renal glomeruli, which is recorded by determining the GFR, there are not only significant violations of intrarenal metabolic processes, but also there is a significant activation of various pathological processes typical of the so-called "diseases of civilization", considered as a pandemic of metabolic pathologies. (first of all, diseases of the cardiovascular system: atherosclerosis and its complications - ischemic stroke, myocardial infarction, etc.). As a result, today specialists have begun to use a new integral concept - "chronic kidney disease" (CKD). This definition should be understood as a cumulative pathophysiological condition with various corresponding nosological disorders. That is, chronic kidney disease is a laboratory diagnosis with certain clinical consequences.

Estimation of glomerular filtration rate by the level of creatinine in the blood

Although high levels of urea and creatinine in the blood are a sign of a decrease in glomerular filtration rate, these indicators are not considered a direct measurement of it. The concentration of these metabolites increases when kidney function is reduced by more than 50%. That is, based on the indicators of creatinine and urea, it is impossible to detect kidney disease at an early stage. Of course, this does not apply to the diagnosis of acute renal failure, the development of which occurs so rapidly that the glomerular filtration rate in any case is reduced by more than 50%. With normal values of the concentration of urea and creatinine in the blood, acute renal failure can be safely excluded. But this is not enough to safely exclude chronic renal failure.

Glomerular filtration rate is ideally assessed by direct measurement. Such a measurement can be carried out, but this method is very complex and expensive, so it is practically not used in everyday practice. Until recently, glomerular filtration rate was measured using the creatinine clearance: the level of creatinine in the blood plasma and the level of creatinine in the daily portion of urine are determined. This method has many disadvantages, one of which is the collection of daily urine. Today, this test is practically not used - since 1999, the glomerular filtration rate has been calculated using a modified formulaMDRD.

GFR = 186 × ([serum (plasma) creatinine + 88.4] -1.154) × age -0.0203 × 0.0742 (female) × 1.21 (black),

where unit of measurement GFR is ml/min; creatinine blood serum (plasma) - µmol/l; age- complete years.

In addition, GFR can be calculated using the MDRD formula (Am. J. Kidney Dis, 2002) based on age, sex, race, and concentrations of creatinine (mmol/l), urea (mmol/l) and albumin (g/dl). ) in blood:

GFR = 170 x (creatinine x 0.0113) -0.999 x age 0.176 x (urea x 2.8) -0.17 x albumin 0.318

The resulting value for women is multiplied by 0.762, for people of the Negroid race - by 1.18.

The latter method of assessment makes it possible to determine the value of the glomerular filtration rate in most patients without resorting to urine collection (that is, without measuring diuresis and creatininuria), thus reducing costs while maintaining clinical information.

Studies have shown that the calculation method for calculating the glomerular filtration rate is much more accurate, as well as more convenient and cheaper than the previously used creatinine clearance. The MDRD method is recommended by many leading medical and scientific institutions and has been mastered by many modern laboratories.

Table 1 shows the values of the glomerular filtration rate and their corresponding stages of chronic renal failure.

TABLE 1. GLOMERULAR FILTRATION RATE (GFR) IN CHRONIC RENAL INSUFFICIENCY (CRF)

Stage	GFR, ml/min	description
		Renal function is normal. There are signs of kidney disease (for example, protein in the urine)
		Moderate decrease in kidney function

		Significant decrease in kidney function
		A sharp decline in kidney function
		Renal failure in the terminal stage

Note that current standards recommend determining the level of creatinine and GFR in all patients with chronic kidney disease every 3-12 months (the frequency of tests depends on the degree of kidney damage). In addition, individuals at high risk of developing kidney disease are advised to have a study every 12 months.

Recommendations for the annual determination of serum (plasma) creatinine levels

Regular testing for the level of creatinine in the blood is recommended for adults with a high risk of developing chronic kidney disease. These patients include:

Diabetes
Cardiac ischemia
Various pathologies associated with atherosclerosis
Heart failure
Hypertonic disease
Rheumatoid arthritis
nephrolithiasis
Systemic lupus erythematosus
Persistent proteinuria
myeloma
Hematuria of unknown etiology
Patients taking long-term drugs with potential nephrotoxic effects

Accurate assessment of glomerular filtration rate

It is necessary to pay attention to the fact that the MDRD formula allows only a rough estimate of the glomerular filtration rate. This formula cannot be used in the case of acute renal failure (although this may not be done with acute renal failure - it is enough to know the level of urea and creatinine in the blood).

Another significant drawback of this formula is that the data obtained using it can be mistaken for reduced kidney function in people with a normal (or almost normal) glomerular filtration rate (60-90 ml / min). That is, using only this formula, one can mistakenly diagnose chronic renal failure of stage 1 or 2 in persons with absolutely normal kidney function. It was this problem that prompted specialists to develop a more accurate formula for calculating the glomerular filtration rate based on the level of creatinine in the blood.

In 2009, studies were carried out on the formula CKD-EPI, which showed that it can be used to determine the glomerular filtration rate much more accurately in individuals with normal or slightly reduced renal function. Most likely in the near future, the CKD-EPI formula will completely replace MDRD.

The kidney consists of a million units - nephrons, which are a glomerulus of vessels and tubules for the passage of fluid.

The nephrons remove waste products from the blood in the urine. Up to 120 liters of liquid pass through them per day. Purified water is absorbed into the blood for the implementation of metabolic processes.

Harmful substances are excreted from the body in the form of concentrated urine. From the capillary, under pressure generated by the work of the heart, liquid plasma is pushed into the glomerular capsule. Protein and other large molecules remain in the capillaries.

If the kidneys are diseased, the nephrons die and no new ones are formed. The kidneys do not perform their cleansing mission well. From the increased load, healthy nephrons fail at an accelerated pace.

To find out the condition of the kidneys, another indicator is also used - the glomerular filtration rate (GFR) of fluid through the nephrons, which in the normal state is 80-120 ml / min. With age, metabolic processes slow down and GFR too.

Fluid filtration passes through the glomerular filter. It consists of capillaries, basement membrane and capsule.

Water with dissolved substances enters through the capillary indothelium, more precisely, through its holes. The basement membrane prevents proteins from entering the renal fluid. Filtration quickly wears out the membrane. Her cells are constantly being renewed.

Purified through the basement membrane, the liquid enters the cavity of the capsule.

The sorption process is carried out due to the negative charge of the filter and pressure. Under pressure, the fluid with the substances contained in it moves from the blood into the glomerular capsule.

GFR is the main indicator of kidney function, and hence their condition. It shows the volume of formation of primary urine per unit of time.

The glomerular filtration rate depends on:

the amount of plasma penetrating the kidneys, the norm of this indicator is 600 ml per minute in a healthy person of average build;
filtration pressure;
filter surface area.

In the normal state, GFR is at a constant level.

Calculation methods

Calculation of the glomerular filtration rate is possible by several methods and formulas.

The determination process is reduced to comparing the content of the control substance in the plasma and urine of the patient. The reference standard is the fructose polysaccharide inulin.

GFR is calculated using the formula:

V urine is the volume of final urine.

The clearance of inulin is a reference indicator in the study of the content of other substances in the primary urine. Comparing the release of other substances with inulin, they study the ways of their filtration from plasma.

When conducting research in a clinical setting, creatinine is used. The clearance for this substance is called Rehberg's test.

Checking kidney function using the Cockcroft-Gault formula

In the morning the patient drinks 0.5 liters of water and urinates into the toilet. Then every hour he collects urine in separate containers. And notes the time of the beginning and end of urination.

For the treatment of kidney diseases, our readers successfully use Galina Savina's method.

To calculate clearance, a certain amount of blood is taken from a vein. The formula calculates the creatinine content.

Formula: F1=(u1/p)v1.

Fi - CF;
U1 - the content of the control substance;
Vi is the time of the first (explored) urination in minutes;
p is the content of creatinine in plasma.

This formula is calculated hourly. The calculation time is one day.

Normal performance

GFR shows the performance of nephrons and the general condition of the kidneys.

The glomerular filtration rate of the kidneys is normally 125 ml / min in men, and in women - 11o ml / min.

In 24 hours, up to 180 liters of primary urine passes through the nephrons. In 30 minutes, the entire volume of plasma is cleared. That is, in 1 day the blood is completely cleared by the kidneys 60 times.

With age, the ability to intensively filter blood in the kidneys slows down.

Help in diagnosing diseases

GFR allows you to judge the state of the glomeruli of nephrons - capillaries through which plasma enters for purification.

Direct measurement involves the constant introduction of inulin into the blood to maintain its concentration. At this time, 4 portions of urine are taken with an interval of half an hour. Then the formula is used to calculate.

This way of measuring GFR is used for scientific purposes. It is too complex for clinical trials.

Indirect measurements are made by creatinine clearance. Its formation and removal are constant and are directly dependent on the amount of muscle mass in the body. In men who lead an active life, creatinine production is higher than in children and women.

Basically, this substance is excreted by glomerular filtration. But 5-10% of it passes through the proximal tubules. Therefore, there is some error in the indicators.

When filtration slows down, the content of the substance increases sharply. Compared to GFR, it is up to 70%. These are signs of kidney failure. The picture of indications can distort the content of drugs in the blood.

And yet, creatinine clearance is a more accessible and generally accepted analysis.

For research, all daily urine is taken with the exception of the first morning portion. The content of the substance in the urine in men should be 18-21 mg / kg, in women - 3 units less. Smaller readings speak of

kidney disease

or improper collection of urine.

The simplest way to assess kidney function is to measure serum creatinine levels. As far as this indicator is increased, GFR is so reduced. That is, the higher the filtration rate, the lower the creatinine content in the urine.

Glomerular filtration analysis is done when kidney failure is suspected.

What diseases can be detected

GFR can help diagnose various forms of kidney disease. With a decrease in the filtration rate, this may be a signal for the manifestation of a chronic form of insufficiency.

For the prevention of diseases and treatment of the kidneys and urinary system, our readers advise

Monastery tea of Father George

It consists of 16 of the most useful medicinal herbs, which are extremely effective in cleansing the kidneys, in the treatment of kidney diseases, urinary tract diseases, and also in cleansing the body as a whole.

The opinion of doctors ... "

At the same time, the concentration of urea and creatinine in the urine increases. The kidneys do not have time to cleanse the blood of harmful substances.

In pyelonephritis, the tubules of the nephrons are affected. The decrease in glomerular filtration rate comes later. The Zimnitsky test will help determine this disease.

The filtration value increases with diabetes mellitus, hypertension, lupus erythematosus and some other diseases.

A decrease in GFR occurs with pathological changes, with a massive loss of nephrons.

The cause may be a decrease in blood pressure, shock, heart failure. Intracranial pressure rises with poor urine outflow. Due to increased venous pressure in the kidney, the filtration process slows down.

How is research conducted in children?

To study GFR in children, the Schwartz formula is used.

The rate of blood flow in the kidneys is higher than in the brain and the heart itself. This is a necessary condition for the filtration of blood plasma in the kidneys.

Reduced GFR can be used to diagnose early kidney disease in children. In clinical conditions, two of the simplest and most informative measurement methods are used.

Research progress

In the morning, on an empty stomach, blood is taken from a vein to determine the level of plasma creatinine. As already mentioned, it does not change during the day.

In the first case, two hourly portions of urine are collected, marking the time of diuresis in minutes. Calculating according to the formula, two GFR values \u200b\u200bare obtained.

The second option is to collect daily urine with an interval of 1 hour. You should get at least 1500 ml.

In a healthy adult, creatinine clearance is 100-120 ml per minute.

In children, a decrease to 15 ml per minute can be alarming. This indicates a decrease in kidney function, their painful condition. This does not always occur from the death of nephrons. It just slows down the filtration rate in each particle.

The kidneys are the most important cleansing organ of our body. If their functioning is disturbed, many organs fail, the blood carries harmful substances, and all tissues are partially poisoned.

Therefore, at the slightest concern in the kidney area, you should take tests, consult a doctor, undergo the necessary examinations and begin timely treatment.

Glomerular filtration rate is one of the main indicators of kidney health. At the initial stage of its formation, urine is filtered as a liquid contained in the blood plasma into the renal glomerulus, through the small vessels located here into the cavity of the capsule. It happens like this:

the capillaries of the kidneys are lined from the inside with a squamous epithelium, between the cells of which there are tiny holes, the diameter of which does not exceed 100 nanometers. Blood cells cannot pass through them, they are too large for this, while the water contained in the plasma and the substances dissolved in it pass freely through this filter,

the next stage is the basement membrane located inside the renal glomerulus. Its pore size is no more than 3 nm, and the surface is negatively charged. The main task of the basement membrane is to separate protein formations present in the blood plasma from the primary urine. Complete renewal of basement membrane cells occurs at least once a year,

finally, the primary urine enters the podocytes - processes of the epithelium of the glomerulus lining the capsule. The size of the pores that are between them is about 10 nm, and the myofibrils present here act as a pump, redirecting the primary urine into the glomerular capsule.

Under the glomerular filtration rate, which is the main quantitative characteristic of this process, we mean the volume of initial urine formed in 1 minute in the kidneys.

The glomerular filtration rate is normal. Result interpretation (table)

The glomerular filtration rate depends on the age and sex of the person. It is usually measured as follows: after the patient wakes up in the morning, he is given about 2 glasses of water to drink. After 15 minutes, he urinates in the usual way, marking the time when urination ends. The patient goes to bed and, exactly one hour after the end of urination, urinates again, already collecting urine. Half an hour after the end of urination, the patient takes blood from a vein - 6-8 ml. An hour after urination, the patient urinates again and again collects a portion of urine in a separate container. The glomerular filtration rate is determined by the volume of urine collected in each portion and by the clearance of endogenous creatinine in serum and in the collected urine.

In a normal healthy middle-aged person, the GFR is normally:

in men - 85-140 ml / min,
in women - 75-128 ml / min.

Then the glomerular filtration rate begins to decrease - by about 6.5 ml / min over 10 years.

The glomerular filtration rate is determined when a number of kidney diseases are suspected - it is it that allows you to quickly identify the problem even before the level of urea and creatinine in the blood rises.

The initial stage of chronic renal failure is considered to be a decrease in the glomerular filtration rate to 60 ml / min. Renal failure can be compensated - 50-30 ml / min and decompensated when GFR drops to 15 ml / min and below. Intermediate values of GFR are called subcompensated renal failure.

A significant decrease in the glomerular filtration rate requires an additional examination of the patient in order to find out if he has kidney damage. If the results of the examination do not show anything, the patient is indicated as a diagnosis of a decrease in the glomerular filtration rate.

The glomerular filtration rate is normal for normal people and for pregnant women:

If the glomerular filtration rate is increased - what does it mean

If the glomerular filtration rate differs from the norm upwards, this may indicate the development of the following diseases in the patient's body:

systemic lupus erythematosus,
hypertension,
nephrotic syndrome,
diabetes.

If the glomerular filtration rate is calculated from creatinine clearance, then you need to remember that taking certain drugs can lead to an increase in its concentration in blood tests.

If the glomerular filtration rate is reduced - what does it mean

The following pathologies can lead to a decrease in the glomerular filtration rate:

heart failure,
dehydration due to vomiting and diarrhea,
decreased thyroid function
liver disease,
acute and chronic glomerulonephritis,
prostate tumors in men.

A steady decrease in glomerular filtration rate to 40 ml/min is commonly referred to as severe renal insufficiency, a decrease to 5 ml/min or less is the end stage of chronic renal failure.

How to evaluate the work of the kidneys? What is SCF?

A healthy kidney consists of 1-1.2 million units of renal tissue - nephrons, functionally associated with blood vessels. Each nephron is about 3 cm long, in turn, consists of a vascular glomerulus and a system of tubules, the length of which in a nephron is 50–55 mm, and all nephrons are about 100 km long. In the process of urine formation, nephrons remove metabolic products from the blood and regulate its composition. 100-120 liters of the so-called primary urine is filtered per day. Most of the liquid is absorbed back into the blood - with the exception of "harmful" and unnecessary substances for the body. Only 1-2 liters of secondary concentrated urine enters the bladder.

Due to various diseases, nephrons one after another are out of order, for the most part irrevocably. The functions of the dead "brothers" are taken over by other nephrons, there are so many of them at first. However, over time, the load on efficient nephrons becomes more and more - and they, having overworked, die faster and faster.

How to evaluate the work of the kidneys? If it were possible to accurately count the number of healthy nephrons, it would probably be one of the most accurate indicators. However, there are other methods as well. It is possible, for example, to collect all the urine of a patient in a day and at the same time analyze his blood - calculate the creatinine clearance, that is, the rate of purification of the blood from this substance.

Creatinine is the end product of protein metabolism. The norm of creatinine content in the blood is 50-100 µmol/l in women and 60-115 µmol/l in men, in children these figures are 2-3 times lower. There are other normal values (not higher than 88 µmol / l), such discrepancies partially depend on the reagents used in the laboratory and on the development of the patient's muscle mass. With well-developed muscles, creatinine can reach 133 µmol/l, with low muscle mass - 44 µmol/l. Creatinine is formed in the muscles, so its slight increase is possible with heavy muscular work and extensive muscle injuries. The kidneys excrete all creatinine, about 1-2 g per day.

However, even more often, to assess the degree of chronic renal failure, such an indicator as GFR is used - the glomerular filtration rate (ml / min).

NORMAL GFR ranges from 80 to 120 ml / min, lower in older people. GFR below 60 ml/min is considered the onset of chronic renal failure.

Here are some formulas to evaluate kidney function. They are quite well known among specialists, I quote them from a book written by specialists from the dialysis department of the St. Petersburg City Mariinsky Hospital (Zemchenkov A.Yu., Gerasimchuk R.P., Kostyleva T.G., Vinogradova L.Yu., Zemchenkova I. .G. "Life with chronic kidney disease", 2011).

This, for example, is the formula for calculating creatinine clearance (the Cockcroft-Gault formula, after the names of the authors of the formula Cockcroft and Gault):

Ccr \u003d (140 - age, years) x weight kg / (creatinine in mmol / l) x 814,

For women, the resulting value is multiplied by 0.85

Meanwhile, in fairness, it must be said that European doctors do not recommend using this formula to assess GFR. To more accurately determine residual kidney function, nephrologists use the so-called MDRD formula:

GFR \u003d 11.33 x Crk -1.154 x (age) - 0.203 x 0.742 (for women),

where Crk is serum creatinine (in mmol/l). If creatinine is given in micromoles (µmol/l) in the test results, this value should be divided by 1000.

The MDRD formula has a significant drawback: it does not perform well at high GFR values. Therefore, in 2009, nephrologists developed a new formula for evaluating GFR, the CKD-EPI formula. The results of the GFR estimate using the new formula are consistent with the MDRD results at low values, but provide a more accurate estimate at high GFR values. Sometimes it happens that a person has lost a significant amount of kidney function, and his creatinine is still normal. This formula is too complicated to be given here, but it is worth knowing that it exists.

And now about the stages of chronic kidney disease:

1 (GFR over 90). Normal or elevated GFR in the presence of disease affecting the kidneys. Observation by a nephrologist is required: diagnosis and treatment of the underlying disease, reducing the risk of developing cardiovascular complications

2 GFR=89-60). Kidney damage with a moderate decrease in GFR. An assessment of the rate of progression of CKD, diagnosis and treatment is required.

3 (GFR=59-30). The average degree of decline in GFR. Prevention, detection and treatment of complications are essential

4 (GFR=29-15). Severe degree of decline in GFR. It's time to prepare for replacement therapy (choice of method is required).

5 (GFR less than 15). Renal failure. Start of renal replacement therapy.

Assessment of glomerular filtration rate by blood creatinine level (abbreviated MDRD formula):

Read more about the work of the kidneys on our website:

* Kidney disease is the silent killer. Professor Kozlovskaya about the problems of nephrology in Russia

* To 3 years in prison - for "selling kidneys"

* Chronic and acute renal failure. From the experience of Belarusian doctors

* The man who performed the world's first kidney transplant

* "New", artificial kidneys - to replace the old, "worn out"?

* Ppoints - the second heart of a person

* How to evaluate the work of the kidneys? What is SCF?

* Test: Checking the kidneys. Do I need to be examined by a doctor?

* More than 170 thousand stones were extracted from the kidneys of an Indian

* What is a kidney biopsy?

* Hereditary kidney disease can be identified by the face

* One can of soda per day increases the risk of kidney disease by almost a quarter

* Chronic kidney disease is the fifth killer disease, the most dangerous for mankind

* How much does kidney disease cost? Another World Kidney Day has passed

* Think about the kidneys from a young age. Early symptoms of kidney disease

* Kidney problems. Urolithiasis, kidney stones, what is it?

* It is better to know about it in advance. Some symptoms of kidney disease

* The most effective remedy for kidney stones is sex!

However, even more often, to assess the degree of chronic renal failure, such an indicator as GFR is used - the glomerular filtration rate (ml / min).

NORMAL GFR ranges from 80 to 120 ml / min, lower in older people. GFR below 60 ml/min is considered the onset of chronic renal failure.

This, for example, is the formula for calculating creatinine clearance (the Cockcroft-Gault formula, after the names of the authors of the formula Cockcroft and Gault):

Ccr \u003d (140 - age, years) x weight kg / (creatinine in mmol / l) x 814,

For women, the resulting value is multiplied by 0.85

GFR \u003d 11.33 x Crk -1.154 x (age) - 0.203 x 0.742 (for women),

where Crk is serum creatinine (in mmol/l). If creatinine is given in micromoles (µmol/l) in the test results, this value should be divided by 1000.

And now about the stages of chronic kidney disease:

2 GFR=89-60). Kidney damage with a moderate decrease in GFR. An assessment of the rate of progression of CKD, diagnosis and treatment is required.

3 (GFR=59-30). The average degree of decline in GFR. Prevention, detection and treatment of complications are essential

4 (GFR=29-15). Severe degree of decline in GFR. It's time to prepare for replacement therapy (choice of method is required).

5 (GFR less than 15). Renal failure. Start of renal replacement therapy.

Assessment of glomerular filtration rate by blood creatinine level (abbreviated MDRD formula):

Read more about the work of the kidneys:

Kidney disease is the silent killer. Professor Kozlovskaya about the problems of nephrology in Russia

To 3 years in prison - for "selling kidneys"

Chronic and acute renal failure. From the experience of Belarusian doctors

The man who performed the world's first kidney transplant

"New", artificial kidneys - to replace the old, "worn out"?

* Ppoints - the second heart of a person

How to evaluate the work of the kidneys? What is SCF?

Test: Checking the kidneys. Do I need to be examined by a doctor?

More than 170 thousand stones were extracted from the kidneys of an Indian

What is a kidney biopsy?

* Hereditary kidney disease can be identified by the face

* One can of soda per day increases the risk of kidney disease by almost a quarter

* Chronic kidney disease is the fifth killer disease, the most dangerous for mankind

* How much does kidney disease cost? Another World Kidney Day has passed

* Think about the kidneys from a young age. Early symptoms of kidney disease

* Kidney problems. Urolithiasis, kidney stones, what is it?

* It is better to know about it in advance. Some symptoms of kidney disease

* The most effective remedy for kidney stones is sex!

Characteristics of the SFR method

Glomerular filtration is measured using certain substances. However, some of them have a number of disadvantages, for example, when using them, it is necessary to conduct continuous IV infusions in order to maintain a constant plasma concentration. In order to calculate the glomerular filtration rate during infusion, at least 4 portions of urine must be collected. Moreover, the collection interval should be strictly 30 minutes. Because of this, this method of research is considered quite expensive and is used only in specialized research institutes.

Most often, the analysis of GFR is carried out on the basis of a study of endogenous creatinine clearance. Creatinine is the end product of the metal process between creatine and creatine phosphate. The kidneys constantly produce and excrete creatinine. Moreover, the speed of this process directly depends on muscle mass. For example, in men who play sports, cretinin is produced in greater volumes than in children, the elderly or women.

This substance is excreted only with the help of GFR. Although some of this substance is excreted through the proximal tubules. Therefore, the glomerular filtration rate, which is determined by creatinine clearance, is sometimes slightly overestimated. If the kidneys are working normally, then the overestimation does not exceed 5-10%.

If there is a decrease in glomerular filtration, then the amount of creatinine secreted increases. If the patient has impaired renal function, this increase can reach 70%.

How to collect urine for analysis

In order for the calculation of GFR to be correct, it is necessary to analyze the daily dose of urine. However, it must be correctly assembled.

To do this, you do not need to take into account urine from the very first morning emptying. But the rest can be collected. And exactly after 24 hours you need to pick up the last batch of liquid. It must be attached to previous materials and sent for research.

The norm of creatinine in the daily dose of urine has the following indicators:

in men - 18-21 mg / kg; in women - 15-18 mg / kg.

If this value is much less, then this may indicate improper urine sampling. Or that the patient has pronounced renal failure and too low muscle mass.

It must be remembered that the container in which the urine is for analysis must be stored in a cold place. Otherwise, uncontrolled growth of bacteria is possible. They will help accelerate the conversion of creatinine to creatine, due to which the clearance value will be significantly below normal.

We must not forget that before starting to collect urine, you need to determine how much creatinine is in the serum. There is a special calculation formula that will help you find out the result. The norm for women is from 75 to 115 ml / min, but for men from 85 to 125 ml / min.

Undoubtedly, the method of diagnosing GFR through creatinine clearance is the surest way to find out the correct result of kidney function.

How to determine the level of kidney function

The most accurate determination of the level of kidney function is in the analysis of creatinine clearance. The higher the creatinine level, the lower the glomerular filtration rate will be.

But external factors that can significantly affect the results of the study should also be taken into account. For example, the level of lean body mass, the weight of the patient, the diet that the patient follows, and much more.

We must not forget about the use of various medications. Some of them may affect the results of the analysis. Still, the results of such a study cannot be neglected. After all, even the slightest change in indications can indicate the development of renal failure. Which in turn will lead to more serious illnesses.

There is a certain formula with which you can analyze the clearance of creatinine. This is the Cockcroft and Gault formula and includes the following characteristics:

patient's age; floor; the weight.

It is with the help of GFR analysis that doctors diagnose the level of kidney failure and make a conclusion about whether the patient should be connected to dialysis or immediately undergo a kidney transplant.

In addition to the results of this study, other indications of the patient should be taken into account. Only on the basis of a comprehensive examination, the doctor can make a final decision.

Treatment of kidney failure

In addition to regular dialysis, the patient may be prescribed other ways to treat kidney failure. These may be preparations that contain calcium and other beneficial substances. Of course, the main task of the doctor is to identify the cause of the disease and begin its immediate treatment.

If we are talking about a preliminary inflammatory process, then you need to identify the type and origin of the infection, and then deal with its elimination. In the case of congenital renal failure, urgent organ transplantation should be performed.

At the same time, one must not forget that a person can live peacefully with one kidney. But for this, the level of its functioning must be above average. This can be determined using GFR analysis.

But every patient should remember that you need to see a doctor when the first symptoms of any disease occur. Only timely diagnosis and correctly prescribed treatment will help the patient restore the working capacity of his body.

Of course, for this you also need to consult experienced and competent specialists and avoid self-treatment methods that can lead to very serious consequences, up to the death of a person.

Modern diagnostic methods

Today, medicine is actively developing. And there are already many ways to diagnose a patient's health status. For example, until recently, ultrasound was considered the most important method. Then new methods began to appear: now it is the well-known computed tomography and other types of modern diagnostics.

But the GFR method for clearing creatinine remains indispensable. It is he who allows you to fully assess the performance of human kidneys and identify the first signs of kidney failure.

The kidneys are the main filter of the human body, and if its work is disrupted, then we can say that other organs will soon “lose their positions” as well.

In addition, a complete stop of the kidneys leads to the death of a person. He needs constant artificial blood purification, which is called dialysis, and therefore is tied to a specific place, namely the hospital. At the same time, the patient cannot afford to go somewhere for a visit or vacation, because with a certain regularity he needs to undergo a dialysis procedure. And it's good if it's free. Otherwise, not everyone has the opportunity to financially master this procedure.

Advantages of the research method

To say that he is the best is incorrect. It must be said that it is the most effective in comparison with other methods of diagnosing kidney function. It is with the help of this method that the doctor can determine at what speed and in what volumes the kidneys can cope with their functions.

It is the method of determining GFR that helps to show the real picture of kidney function.

And if it suddenly becomes clear that the kidneys are not performing their functions well, then the doctor immediately applies the necessary treatment and looks for a way to help this organ by artificial methods. Most often, it is the analysis of GFR that shows that the kidneys are not working well, and the patient needs urgent transplantation.

As a result, it is possible to save the life of the patient and restore his normal lifestyle.

But in order to make such an analysis, the patient must contact a professional nephrologist or urologist, and only after that he undergoes this examination.

It is always worth remembering that everything related to health must be done on time and according to established rules. Then the treatment will be effective and timely, and the result will be unambiguously positive.

The kidney consists of a million units - nephrons, which are a glomerulus of vessels and tubules for the passage of fluid.

Methods to evaluate kidney function

To do this, collect the daily urine of the patient and calculate the content of creatinine in the blood. Creatinine is a protein breakdown product. Comparison of indicators with reference values shows how well the kidneys cope with the function of cleansing the blood from decay products.

Fluid filtration passes through the glomerular filter. It consists of capillaries, basement membrane and capsule.

Purified through the basement membrane, the liquid enters the cavity of the capsule.

GFR is the main indicator of kidney function, and hence their condition. It shows the volume of formation of primary urine per unit of time.

The glomerular filtration rate depends on:

the amount of plasma penetrating the kidneys, the norm of this indicator is 600 ml per minute in a healthy person of average build; filtration pressure; filter surface area.

In the normal state, GFR is at a constant level.

Calculation methods

Calculation of the glomerular filtration rate is possible by several methods and formulas.

The determination process is reduced to comparing the content of the control substance in the plasma and urine of the patient. The reference standard is the fructose polysaccharide inulin.

GFR is calculated using the formula:

V urine is the volume of final urine.

When conducting research in a clinical setting, creatinine is used. The clearance for this substance is called Rehberg's test.

For the treatment of kidney diseases, our readers successfully use Galina Savina's method.

Checking kidney function using the Cockcroft-Gault formula

In the morning the patient drinks 0.5 liters of water and urinates into the toilet. Then every hour he collects urine in separate containers. And notes the time of the beginning and end of urination.

To calculate clearance, a certain amount of blood is taken from a vein. The formula calculates the creatinine content.

Formula: F1=(u1/p)v1.

Fi - CF; U1 - the content of the control substance; Vi is the time of the first (explored) urination in minutes; p is the content of creatinine in plasma.

This formula is calculated hourly. The calculation time is one day.

Normal performance

GFR shows the performance of nephrons and the general condition of the kidneys.

The glomerular filtration rate of the kidneys is normally 125 ml / min in men, and in women - 11o ml / min.

With age, the ability to intensively filter blood in the kidneys slows down.

Help in diagnosing diseases

GFR allows you to judge the state of the glomeruli of nephrons - capillaries through which plasma enters for purification.

This way of measuring GFR is used for scientific purposes. It is too complex for clinical trials.

Basically, this substance is excreted by glomerular filtration. But 5-10% of it passes through the proximal tubules. Therefore, there is some error in the indicators.

And yet, creatinine clearance is a more accessible and generally accepted analysis.

kidney disease

or improper collection of urine.

Glomerular filtration analysis is done when kidney failure is suspected.

For the prevention of diseases and treatment of the kidneys and urinary system, our readers advise

Monastery tea of Father George

The opinion of doctors ... "

What diseases can be detected

GFR can help diagnose various forms of kidney disease. With a decrease in the filtration rate, this may be a signal for the manifestation of a chronic form of insufficiency.

At the same time, the concentration of urea and creatinine in the urine increases. The kidneys do not have time to cleanse the blood of harmful substances.

In pyelonephritis, the tubules of the nephrons are affected. The decrease in glomerular filtration rate comes later. The Zimnitsky test will help determine this disease.

The filtration value increases with diabetes mellitus, hypertension, lupus erythematosus and some other diseases.

A decrease in GFR occurs with pathological changes, with a massive loss of nephrons.

How is research conducted in children?

To study GFR in children, the Schwartz formula is used.

The rate of blood flow in the kidneys is higher than in the brain and the heart itself. This is a necessary condition for the filtration of blood plasma in the kidneys.

Reduced GFR can be used to diagnose early kidney disease in children. In clinical conditions, two of the simplest and most informative measurement methods are used.

Research progress

In the morning, on an empty stomach, blood is taken from a vein to determine the level of plasma creatinine. As already mentioned, it does not change during the day.

In the first case, two hourly portions of urine are collected, marking the time of diuresis in minutes. Calculating according to the formula, two GFR values \u200b\u200bare obtained.

The second option is to collect daily urine with an interval of 1 hour. You should get at least 1500 ml.

In a healthy adult, creatinine clearance is 100-120 ml per minute.

The kidneys are the most important cleansing organ of our body. If their functioning is disturbed, many organs fail, the blood carries harmful substances, and all tissues are partially poisoned.

Therefore, at the slightest concern in the kidney area, you should take tests, consult a doctor, undergo the necessary examinations and begin timely treatment.

The kidney consists of a million units - nephrons, which are a glomerulus of vessels and tubules for the passage of fluid.

Methods to evaluate kidney function

Fluid filtration passes through the glomerular filter. It consists of capillaries, basement membrane and capsule.

Purified through the basement membrane, the liquid enters the cavity of the capsule.

GFR is the main indicator of kidney function, and hence their condition. It shows the volume of formation of primary urine per unit of time.

The glomerular filtration rate depends on:

the amount of plasma penetrating the kidneys, the norm of this indicator is 600 ml per minute in a healthy person of average build;
filtration pressure;
filter surface area.

In the normal state, GFR is at a constant level.

Calculation methods

Calculation of the glomerular filtration rate is possible by several methods and formulas.

The determination process is reduced to comparing the content of the control substance in the plasma and urine of the patient. The reference standard is the fructose polysaccharide inulin.

GFR is calculated using the formula:

V urine is the volume of final urine.

When conducting research in a clinical setting, creatinine is used. The clearance for this substance is called.

Checking kidney function using the Cockcroft-Gault formula

In the morning the patient drinks 0.5 liters of water and urinates into the toilet. Then every hour he collects urine in separate containers. And notes the time of the beginning and end of urination.

To calculate clearance, a certain amount of blood is taken from a vein. The formula calculates the creatinine content.

Formula: F1=(u1/p)v1.

Fi – CF;
U1 is the content of the control substance;
Vi is the time of the first (explored) urination in minutes;
p is the content of creatinine in plasma.

This formula is calculated hourly. The calculation time is one day.

Normal performance

GFR shows the performance of nephrons and the general condition of the kidneys.

The glomerular filtration rate of the kidneys is normally 125 ml / min in men, and in women - 11o ml / min.

With age, the ability to intensively filter blood in the kidneys slows down.

Help in diagnosing diseases

GFR allows you to judge the state of the glomeruli of nephrons - capillaries through which plasma enters for purification.

This way of measuring GFR is used for scientific purposes. It is too complex for clinical trials.

Basically, this substance is excreted by glomerular filtration. But 5-10% of it passes through the proximal tubules. Therefore, there is some error in the indicators.

When filtration slows down, the content of the substance increases sharply. Compared to GFR, it is up to 70%. These are signs. The picture of indications can distort the content of drugs in the blood.

And yet, creatinine clearance is a more accessible and generally accepted analysis.

Glomerular filtration analysis is done if you suspect.

What diseases can be detected

GFR can help diagnose various forms of kidney disease. With a decrease in the filtration rate, this may be a signal for the manifestation of a chronic form of insufficiency.

The filtration value increases with diabetes mellitus, hypertension, lupus erythematosus and some other diseases.

A decrease in GFR occurs with pathological changes, with a massive loss of nephrons.

How is research conducted in children?

To study GFR in children, the Schwartz formula is used.

The rate of blood flow in the kidneys is higher than in the brain and the heart itself. This is a necessary condition for the filtration of blood plasma in the kidneys.

Reduced GFR can be used to diagnose early kidney disease in children. In clinical conditions, two of the simplest and most informative measurement methods are used.

Research progress

In the morning, on an empty stomach, blood is taken from a vein to determine the level of plasma creatinine. As already mentioned, it does not change during the day.

In the first case, two hourly portions of urine are collected, marking the time in minutes. Calculating according to the formula, two GFR values \u200b\u200bare obtained.

The second option is to collect daily urine with an interval of 1 hour. You should get at least 1500 ml.

In a healthy adult, creatinine clearance is 100-120 ml per minute.

The kidneys are the most important cleansing organ of our body. If their functioning is disturbed, many organs fail, the blood carries harmful substances, and all tissues are partially poisoned.

Therefore, at the slightest concern in the kidney area, you should take tests, consult a doctor, undergo the necessary examinations and begin timely treatment.

Glomerular filtration rate calculation - online calculator and Cockcroft formula. How is glomerular filtration rate measured?

Literature

Questions and answers

Clinical significance of glomerular filtration rate

Estimation of glomerular filtration rate by the level of creatinine in the blood

Recommendations for the annual determination of serum (plasma) creatinine levels

Accurate assessment of glomerular filtration rate

Calculation methods

Checking kidney function using the Cockcroft-Gault formula

Normal performance

Help in diagnosing diseases

What diseases can be detected

How is research conducted in children?

Research progress

The glomerular filtration rate is normal. Result interpretation (table)

If the glomerular filtration rate is increased - what does it mean

If the glomerular filtration rate is reduced - what does it mean

Characteristics of the SFR method

How to collect urine for analysis

How to determine the level of kidney function

Treatment of kidney failure

Modern diagnostic methods

Advantages of the research method

Methods to evaluate kidney function

Calculation methods

Checking kidney function using the Cockcroft-Gault formula

Normal performance

Help in diagnosing diseases

What diseases can be detected

How is research conducted in children?

Research progress

Methods to evaluate kidney function

Calculation methods

Checking kidney function using the Cockcroft-Gault formula

Normal performance

Help in diagnosing diseases

What diseases can be detected

How is research conducted in children?

Research progress

Questions
and answers