Introduction
The stages are classified according to several different criteria. The higher the stage, the worse the kidney function is and the higher the risk of dying from the disease. Furthermore, the therapy is based on the stage classification.
As a rule, the classification is based on the glomerular filtration rate. In addition, albuminuria is also considered to be a factor independent of the classification. Albuminuria describes how much protein passes through the kidney into the urine. In a healthy person, there should be no protein in the urine. The classification based on 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, renal function is described by stages (stages 1-5) (see below).
- Classification by course
- Classification by glomerular filtration rate
- Classification by retention values
Since chronic renal failure is a progressive disease, the stages of the disease reflect the course of renal failure.
The more the disease progresses, the worse the kidney function becomes, which manifests itself not only in increasing symptoms but also in certain poorer blood and urine values. With further progression and increasing stage, the risk of dying from renal failure increases. In the kidney there are small structures called glomerulus.
The blood is filtered into this glomerulus and the primary urine is formed, which in other structures is slightly changed in its composition before it leaves the body. If the glomerulus is destroyed, the kidney function is impaired. If too many glomeruli are dead, the kidney is no longer able to fulfill its function sufficiently.
The glomerular filtration quantity indicates how much primary urine is produced by all glomeruli in one minute. Therefore, it is a relatively good parameter for the classification of chronic renal insufficiency. The glomerular filtration rate of a healthy person is between 75 and 145 ml/min.
According to the National Kidney Foundation, chronic renal insufficiency can be divided into five stages based on the renal function parameter “glomerular filtration rate” (GFR, ml per min per 1.73 m3). Stage 5 is renal failure and renal replacement therapy is necessary to keep the patient alive. If the GFR is greatly reduced, it is important to note that the intake of many medications, for example painkillers, must be adapted to the impaired kidney function.
- Renal damage with normal renal function: GFR ≥ 90
- Renal damage with mild renal insufficiency: GFR 60-89
- Moderate renal failure: GFR 30-59
- Severe renal failure: GFR 15-29
- Renal failure:GFR < 15
Retention values include various blood values of substances that are urinary and must be excreted via the kidney. These substances include urea, creatinine and uric acid. An increase in these values indicates that there is not everything wrong with the kidney function.
If these values are constantly increased over a longer period of time, they can be an indication of chronic renal insufficiency. If stage classification is based on retention values, other criteria such as symptoms must also be taken into account. Kidney failure is only divided into 4 stages here, with stage 4 being renal failure.
Stage 1 Stage 1 is often a very unremarkable stage. It causes little or no discomfort and in many cases is not recognized. In stage 1, which is classified according to the glomerular filtration rate, the glomerular filtration rate is not yet impaired, but there is still a slight functional impairment of the kidney.
This manifests itself in existing kidney damage, which is reflected in non-standard blood or urine values or abnormal imaging of the kidney, e.g. ultrasound. A possible indication is e.g. protein in the urine. If the cause of the slightly impaired renal function can be identified, renal insufficiency is still well treatable and a progression of the disease can be effectively counteracted.Confusingly, stage 1, when the retention parameters are used to classify, describes a stage in which there is 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 lies between 60 and 89 ml/min. This alone does not necessarily have to be a sign of disease, since the glomerular filtration rate of the kidney normally decreases with increasing age, even in healthy individuals.
As in stage 1, abnormal blood or urine values or abnormal imaging must be added to the data in order to diagnose chronic renal failure in stage 2. There may be mild symptoms such as increased urine excretion, elevated blood pressure, water retention in the legs or pain in the kidney bed. Stage 2 according to the retention parameters is characterized by a moderate increase in creatinine levels.
However, there are still no or hardly any complaints. Doctors therefore speak of renal insufficiency with compensated retention. Stage 3 In stage 3, the glomerular filtration rate has again deteriorated significantly.
It lies between 30 and 59 ml/min. At this stage at the latest, various symptoms occur due to the reduced renal function. In addition to the symptoms described above, itching, tiredness and reduced performance may occur.
In addition, the risk of cardiovascular diseases increases. In stage 3 of the classification according to the retention values, we speak of renal insufficiency with decompensated retention. This means that symptoms occur and the retention parameters, primarily creatinine, have increased very significantly.
Stage 4 In stage 4, the glomerular filtration rate is very limited and it is foreseeable that the kidney function will deteriorate to such an extent that the kidney is no longer able to perform vital functions. Therefore, preparations for a renal replacement procedure are being made in stage 4. The symptoms of the affected patients may continue to increase.
They may also experience vomiting, nausea, muscle twitching, weight loss and other symptoms. When classified according to retention values, stage 4 already describes a kidney failure with dialysis duty. Acute renal insufficiency: There are three forms of acute renal insufficiency: In prerenal renal failure, the cause of renal insufficiency is due to changes in renal blood flow (perfusion).
This is reduced, which is why a hormone-enzyme cascade, the renin-angiotensin-aldosterone system (RAAS), is set in motion to compensate. As a result of this hormonal regulatory chain, less urine is excreted; the kidneys lose function and renal insufficiency develops.
- Prerenal kidney failure: “before the kidney”, approx.
60%.
- Intrarenal renal failure: “within the kidney”, approx. 35%
- Postrenal kidney failure: “after the kidney”, approx. 5%.