Internal Medicine

Stages of renal failure

introduction

The staging is based on several different criteria. The higher the stage, the worse the kidney function and the higher the risk of dying from the disease. Furthermore, the therapy is based on the staging. As a rule, this is based on the classification according to the glomerular filtration rate. In addition, albuminuria is also considered to be a non-classification-independent factor. Albuminuria describes how much protein passes through the kidneys into the urine. A healthy person shouldn't have any protein in the urine. The classification based on the retention values is often not so relevant in the clinic.

Classification of renal insufficiency

Renal insufficiency can be classified as follows:

Classification according to course
Classification according to glomerular filtration rate
Classification according to retention values

As a rule, the classification is based on the glomerular filtration rate. Overall, kidney function is described using stages (stages 1-5) (see below).

Classification of renal insufficiency according to course

Since chronic renal failure is a progressive disease, the staging reflects the course of renal failure. The further the disease progresses, the worse the kidney function becomes, which, in addition to increasing symptoms, is also expressed in certain poorer blood and urine values. As the disease progresses and the stage increases, the risk of dying from kidney failure increases.

Renal failure causes many typical symptoms. If you want to know more about it, please also read: Symptoms of renal insufficiency

Classification of renal insufficiency according to GFR

There are small structures in the kidney called the glomerulus. In this glomerulus the blood is filtered and the primary urine is formed, the composition of which is slightly changed in other structures before it leaves the body. Renal function is impaired by the sinking of the glomerulus. If too many glomeruli have died, the kidney is no longer able to function properly. The glomerular filtration rate indicates how much primary urine is produced by all glomeruli in one minute. It is therefore a relatively good parameter for classifying chronic kidney failure. The glomerular filtration rate of a healthy person is between 75 and 145 ml / min.

According to the National Kidney Foundation, chronic kidney failure can be determined using the kidney function parameter "glomerular filtration rate“(GFR, ml per min per 1.73 m3) into five stages. In stage 5, kidney failure is present and renal replacement therapy is necessary to keep the affected person alive.

Kidney damage with normal kidney function: GFR ≥ 90
Kidney damage with mild renal insufficiency: GFR 60-89
Moderate renal insufficiency: GFR 30-59
severe renal insufficiency: GFR 15-29
Kidney failure: GFR <15

If the GFR is severely reduced, it should be noted that the intake of many medications, for example painkillers, must be adapted to the impaired kidney function.

You can find more about this at: Pain relievers for kidney disease

Classification of renal insufficiency according to retention values

Retention values include various blood values of substances that require urine and must be excreted via the kidneys. These substances include e.g. Urea, creatinine and uric acid. An increase in these values indicates that the kidneys are not functioning properly. If these values are steadily increased over a longer period of time, they can be an indication of chronic kidney failure. When staging is based on retention values, other criteria, such as symptoms, need to be considered. The renal insufficiency is only divided into 4 stages, with stage 4 being kidney failure.

Stages of renal failure

Stage 1

Stage 1 is often a very inconspicuous stage. It causes little or no discomfort and in many cases is not recognized.In stage 1 of the classification according to the glomerular filtration rate, the glomerular filtration rate is not yet impaired, but there is still a slight functional restriction of the kidneys. This manifests itself in existing kidney damage, which manifests itself in non-normal blood or urine values or abnormal imaging of the kidney, e.g. on ultrasound, shows. A possible hint is e.g. Protein in the urine. If the cause of the slightly impaired kidney function can be identified, the kidney failure can still be treated well and the progression of the disease can be effectively counteracted. Confusingly, stage 1 describes, if classification is based on the retention parameters, a stage in which there is still no change in the retention parameters, but the glomerular filtration rate is slightly reduced.

Stage 2

In stage 2 the glomerular filtration rate is slightly reduced. It is between 60 and 89 ml / min. This alone does not have to have any disease value, since the glomerular filtration rate of the kidneys normally decreases with increasing age, even in healthy people. As with stage 1, abnormal blood or urine values or abnormal imaging must also be added so that chronic kidney failure can be diagnosed in stage 2. There may be mild symptoms such as increased urine output, increased blood pressure, water retention in the legs or pain in the kidney bed. Stage 2 according to the retention parameters is noticeable by a moderate increase in the creatinine value. However, there are no or hardly any complaints. Doctors therefore speak of renal insufficiency with compensated retention.

Stage 3

In stage 3, the glomerular filtration rate deteriorated again significantly. It is between 30 and 59 ml / min. Now at the latest, various symptoms appear due to the reduced kidney function. In addition to the symptoms described above, itching, tiredness and reduced performance can occur. In addition, the risk of cardiovascular diseases increases. In stage 3 of the classification according to the retention values, one speaks of renal insufficiency with decompensated retention. Which means that complaints occur and the retention parameters, primarily creatinine, have risen very significantly.

For more information on the symptoms of kidney failure, we recommend our website: Symptoms of renal insufficiency

Stage 4

In stage 4, the glomerular filtration rate is very limited and it is foreseeable that kidney function will deteriorate to such an extent that the kidney is no longer able to perform vital functions. Therefore, in stage 4, preparations are made for a kidney replacement procedure. The complaints of those affected may have continued to increase. There is also vomiting, nausea, muscle twitching, weight loss and other symptoms. When classified according to the retention values, stage 4 already describes kidney failure with dialysis.

For more information, see: Symptoms of renal insufficiency or dialysis

Stage 5

If kidney failure occurs at a glomerular filtration rate of less than 15 ml / min, it is called stage 5. Then a kidney replacement procedure, such as dialysis or a kidney transplant, is necessary, otherwise the patient will die.

You can find more information on Ablaut dialysis at: dialysis

If you are interested in the process and life expectancy after a kidney transplant, please also read: Kidney Transplant and Life Expectancy in Renal Failure

Causes renal failure

Acute renal failure: There are three forms of acute renal failure:

prerenal kidney failure: "before the kidney", Approx. 60%
intrarenal kidney failure: "Within the kidney", approx. 35%
postrenal renal failure: "After the kidney", approx. 5%

At the prerenal kidney failure is the cause of kidney failure due to changes in kidney blood flow (Perfusion). This is reduced, which is why a compensatory one Hormone-enzyme cascade, the R.enin-A.ngiotensinA.ldosteroneS.ystem (RAAS) is started. As a result of this chain of hormonal regulation, less urine is excreted; the kidneys lose their function and renal insufficiency develops.

There are several causes for a reduced blood flow, for example an overall reduced blood volume, a decrease in the delivery rate of the Heart (Cardiac output) and blood pressure, systemic vasodilation (Vasodilation) with "sinking" of the blood in peripheral vessels or vascular constrictions in the kidney self.

At intrarenal renal failure The cause of the loss of function lies in changes in the kidney structure itself. Inflammation of the blood vessels or kidney tissue, blood clots (Thromboembolism), Medication, Toxins or roentgen - contrast media.

The final form that postrenal renal failure, is characterized by changes in the urinary tract downstream of the kidneys, which means that the urine can no longer or only poorly be excreted. Reasons for this are, for example, congenital or acquired malformations, Tumors or medication

Chronic renal failure: Chronic kidney failure can be on the ground several different Kidney disease develop. These include, for example diabetic nephropathy (Kidney damage in long-term Diabetes mellitus), Glomerulonephritis (Inflammation of the kidney structural units "glomeruli"), vascular nephropathies (damage to the vessels as the cause) or polycystic kidney diseases (cystic changes in the kidney structure).

Characteristic for a chronic renal failure are the failure of elimination with subsequent organ damage due to the accumulation of urinary substances in the body, disturbances in the water, electrolyte and acid-base balance as well as a decrease in the hormonal kidney function (formation of renin, prostaglandins, Vitamin D, Erythropoietin).