Reberg’s test

Based on the results of the Rehberg test (Russian synonym for glomerular filtration rate), the doctor evaluates the excretory function of the kidneys by determining endogenous creatinine clearance – a study used to assess the level of glomerular filtration and tubular reabsorption.

What is the importance of the Rehberg test?

All human blood passes through the kidneys several hundred times a day. Through tiny filters (nephrons) they pass the liquid part of the blood, and then most of the liquid is reabsorbed back into the blood. Liquid waste that is not reabsorbed by the kidneys is eliminated from the body in the urine. Creatinine (from the Greek kreas – “flesh”) is a breakdown product of creatine phosphate in muscle tissue. Its amount in the body is constant and depends on the muscle mass of a person. Creatinine is filtered from the blood by the kidneys. A small amount is actively excreted in the urine. Tubular reabsorption of creatinine is minimal. But if the filtering ability of the kidneys is insufficient, then the level of creatinine in the blood increases. Knowing the levels of creatinine in and urine, you can calculate the creatinine clearance, which will reflect the level of glomerular filtration. Creatinine clearance (from the English clearance – “purification”, that is, cleansing from creatinine, its excretion) is the amount of blood that the kidneys can clear of creatinine within one minute. Creatinine clearance can be determined in two ways, namely by measuring the amount of creatinine in a person’s blood and daily urine. A more convenient blood test for the patient, therefore, such an analysis is more often used in practice.

In what situations is the Reberg test prescribed to the patient?

If a patient has pain in the kidney area, swelling around the eyes and ankles, hypertension, reduced amount of urine or problems with urination, dark urine, blood in the urine, Alport syndrome, amyloidosis, chronic renal failure, Cushing’s syndrome, dermatomyositis, sugar diabetes, intoxication with cardiac glycosides, generalized attacks of tonic-clonic seizures, Goodpasture’s syndrome, hemolytic uremic syndrome, hepatorenal syndrome, interstitial nephritis, lupus nephritis, malignant arterial hypertension, membranoproliferative glomerulonephritis, thrombocytopenic purpura, Wilms’ tumor, factors affecting kidney function, Reberg’s test is prescribed.

Normal tubular reabsorption rates start at 95 percent or more. If the level drops to 90 percent, then this indicates pathological processes occurring in the kidneys. This situation can be observed when consuming a large amount of liquid or diuretics – drugs with a diuretic effect. Glomerular filtration is reduced in patients with acute or chronic nephritis, kidney damage caused by persistent hypertension, or diabetes mellitus.

Kidney failure and an increase in nitrogenous waste in the blood may be the result of a decrease in glomerular filtration by up to about 80-85 percent. In chronic pyelonephritis, glomerular filtration decreases slowly, with violations of the renal concentration ability, this happens faster.

If, according to the results of the Rehberg test, glomerular filtration has decreased to 40 ml per minute, then we can talk about the diagnosis of chronic renal failure.

How do I prepare for the analysis?

A week before the Reberg test, it is advisable for the patient to refrain from any physical activity. It is also worth excluding coffee, strong tea, alcoholic beverages and any kind of meat from the diet.

It is necessary to pay attention to the drugs that were previously taken and inform the attending physician about this. Drugs such as corticotropin, cortisol, thyroxine, methylprednisolone, furosemide and other drugs included in similar groups of pharmacological action can significantly affect the filtration rate. Therefore, be sure to list to the doctor everything that you are taking now or have taken in the last 14 days.

What is required to take the Rehberg Test?

Daily urine is collected for laboratory research. It is very important to assemble it correctly, since the slightest errors can significantly affect the results of the analysis. It is important to remember that all urine (except the first morning portion) is collected in a pre-disinfected dry container. Urine collected during the day should be kept in a cool place.

After accurate fixation of the volume of daily urine, 60 milliliters are taken for analysis, and the anthropometric data of the patient are recorded in parallel. These are important components that affect the results of the analysis. It is very important to donate blood on the same day to determine the concentration of creatinine.

Deciphering the results

In a healthy young person, creatinine clearance is about 125 ml per minute. And this means that every minute the kidneys clear 125 ml of blood from creatinine. The level of glomerular filtration is the sum of filtration levels in all functioning nephrons. This indicator allows you to determine the number of nephrons in the kidneys, is of great clinical importance, since it is the main characteristic of kidney function. In severely impaired renal function, creatinine clearance increases, since the active secretion of creatinine releases a larger fraction of it. Ketone acids, trimethoprim and cimetidine limit tubular secretion of creatinine, reduce the accuracy of glomerular filtration, especially in severe renal failure.

If, after passing the analysis, the specialists determined that the indicators exceed the normal values, it is likely that the patient has the initial stage of diabetes mellitus, chronic high blood pressure, or nephrotic syndrome.

With reduced results, the patient may have reduced renal function or renal failure.

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