What is it about ?
The kidneys are made up of millions of microscopic filters (the glomeruli). Blood flows continuously through these filters. Filters permanently clean the blood: they rid the blood of excess waste and water, and keep the amount of salts within certain limits. What is in excess is evacuated via the urine.
Sometimes these filters are damaged. This destabilizes the water balance in the body. Some wastes can build up in the blood.
If the kidney filters keep getting damaged, they eventually don’t work at all. In this case, the waste remains in the blood, which can be toxic to the body.
Several tests are used to assess the filtration function of the kidneys.
Creatinine is a breakdown product of muscles, therefore waste. The kidneys constantly filter it from the blood and eliminate it in the urine. The concentration of creatinine in the blood is therefore a good parameter to determine the functioning of the kidneys. The less they work, the more creatinine there is in the blood.
Renal function can be assessed via a estimation of glomerular filtration rate (EGFR), based on the creatinine level in the blood. The eGFR indicates how much blood the kidneys can filter per minute.
- In a healthy person, the kidneys filter more than 90 milliliters of blood per minute.
- This rate decreases with age. In the elderly, a rate of 30 to 45 milliliters per minute is still normal.
- The amount of creatinine can vary greatly from person to person. For example, men have more creatinine in their blood than women and the elderly. This is because they are generally more muscular and taller.
Due to these differences, it is not always clear whether creatinine, and therefore kidney function, is still normal. What may turn out to be too high in one person may not be so high in another. A blood test can provide additional information in this regard.
If it is necessary calculate kidney function accurately, and it is therefore impossible to be satisfied with an estimate, your doctor will ask you to keep your urine for 24 hours. Kidney function can be calculated more accurately based on the volume of urine produced and the concentration of creatinine in urine and blood.
Based on these 2 tests, we can therefore get an idea of the kidney function and the severity of possible kidney failure.
Classification of renal failure
Glomerular filtration rate is used to define the severity of renal failure: from stage 1 (least severe) to stage 5 (most severe).
- Stage 1: normal. The flow rate is greater than 90 milliliters per minute.
- Stage 2: mild renal failure. Flow rate between 60 and 89 milliliters per minute.
- Stage 3: moderate renal failure. Flow rate between 30 and 59 milliliters per minute.
- Stage 4: severe renal failure. Flow rate between 15 and 29 milliliters per minute.
- Stage 5: end-stage renal failure. Flow less than 15 milliliters per minute.
At stage 2, no other additional examinations are planned, unless there is also blood and / or protein in the urine, as well as in patients diabetics.
From stage 3, kidney failure should be treated.
Stage 5 patients are candidates for kidney dialysis and possibly a kidney transplant.
What tests are done if the creatinine level is too high in the blood?
The doctor will start by asking a series of questions:
- Do you have a history of kidney disease?
- Do you have any other conditions that can influence kidney function, such as diabetes, arteriosclerosis, rheumatism, enlarged prostate, etc. ?
- Do you take medication ?
- Have contrast agents recently been used in exams?
A thorough clinical examination will follow:
- Condition ;
- Blood pressure ;
- Examination of the abdomen and prostate in men;
- Pulse control in the arteries of the arms and legs;
- Control of water retention in the legs.
Finally, several technical examinations are carried out: and a ultrasound kidneys. Additional examinations may be considered depending on the results.
The role of the general practitioner and the specialist
The diagnosis, initiation and optimization of treatment are the responsibility of the kidney specialist (nephrologist). Intermediate checks are carried out at the general practitioner, in consultation with the specialist. The general practitioner will redirect if he notices a deterioration in renal function. In the presence of acute illness with fever, symptoms of respiratory tract infection andjoint infections, it will be advisable to consult the nephrologist. In all of these cases, kidney function can quickly decline.
So that the collaboration takes place in the best conditions, it is possible to set up what is called a renal failure treatment path. All people over the age of 18 with a flow rate of less than 45 milliliters per minute are eligible for this treatment path. This provides a number of advantages, such as a free blood pressure monitor, free consultations with a nephrologist and the general practitioner, reimbursement of dietitian fees as well as free medicines. People treated by kidney dialysis or those who have had a kidney transplant cannot benefit from the renal failure treatment path. A suitable program is planned for these patients.
Want to know more?
- Urine test – 24 hour collection – CHU Montreal
- Ultrasound here Where to find on this page of Cliniques St Luc UCL
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