Acute kidney failure is often barely detectable by the affected person and only at an advanced stage. It is usually completely painless. There are cases in which acute kidney failure is accompanied by a cessation of urine production, this is known as anuria.
A reduction in urine production to less than 500 ml urine excretion per day (oliguria) is also possible. However, this is not always the case. There is also kidney failure with normal or even excessive urine production.
Because the damaged kidney accumulates the substances that are normally excreted sufficiently, hyperkalemia can occur. Hyperkalemia means that there is too much potassium in the blood. This can lead to dangerous heart rhythm disturbances.
Restricted kidney function can also lead to the organism being overloaded with urinary substances, which is known as uremia. Possible symptoms of uremia can be lack of concentration and tiredness, the symptoms can then increase to disorientation and drowsiness. Other possible symptoms of acute uremia are nausea and vomiting as well as itching.
Overhydration can also be an indication of acute kidney failure. Water retention in the legs (lower leg edema) may occur or overhydration of the lungs with the development of pulmonary edema. This can manifest itself as shortness of breath (dyspnoea) and rattling, “bubbling” breath sounds.
Pain does not occur in acute kidney failure. Therefore, the diagnosis is also significantly more difficult. The symptoms that occur in acute kidney failure are very varied and unspecific.
Decisive indications are given by blood tests (here especially with regard to laboratory values such as urea, creatinine, blood gases, acid-base status) and urine diagnostics. An examination of the urine for excreted red blood cells (erythrocytes) and proteins (so-called proteinuria) is absolutely necessary! This allows the location of the damage to be determined, which is of great importance for the further procedure. If the cause remains unclear, a kidney biopsy should be considered. Alternative diseases, which can be associated with similar causes, are
- Acute deterioration of renal function in the context of chronic renal insufficiency
- Acute bacterial nephritis
Causes of kidney failure
While acute kidney failure is often caused by acute diseases, injuries or poisoning, chronic kidney failure is usually the result of a long-standing underlying disease. In order to describe the causes of acute kidney failure more clearly, they have been divided into three categories:
- Intrarenal and
- Postrenal acute renal failure. Here prerenal means “before the kidney”, intrarenal “within the kidney” and postrenal “behind the kidney”.
The prerenal kidney failure is caused by changes in the blood circulation in front of the kidney. Thus, the kidney itself is not damaged at the beginning. Reasons for such kidney failure can be In this case, the circulation is centralized so that only the most important organs like the heart and brain are supplied with oxygen.
Both causes lead to a lack of blood circulation in the kidney and thus to a lack of oxygen, which leads to the destruction of kidney tissue. But poisoning of the kidney can also lead to its failure. The poisons cause a narrowing of the blood vessels in the kidney and thus also a lack of blood circulation and thus a reduced oxygen supply.
The intrarenal kidney failure is caused by changes or diseases of the kidney itself. Causes include In addition to these causes, toxins and numerous drugs can also cause tissue damage. Postrenal acute kidney failure is caused by a shift of the urinary tract after the kidney.
The reasons for this are:
- Massive loss of volume, e.g. due to severe blood loss
- Or a so-called shock kidney for circulatory instability. – a prolonged prerenal kidney failure,
- Blockage of the kidney ducts due to massive blood loss,
- Urate or a
- Massive decay of muscle cells rhabdomyolysis. Also
- Blood clot or
- Metabolic diseases (e.g. Wegener’s disease) can clog the vessels in the kidneys.
- Ureteral stones,
- Congenital narrowing of the ureters,
- Obstruction of the bladder due to bladder tumours or
- Blocked bladder catheters but also
- Narrowing of the urethra due to external tumours, such as a large prostate tumour. A typical group of drugs that can cause kidney failure are painkillers from the group of non-steroidal anti-inflammatory drugs. These include the widely used painkillers ibuprofen and diclofenac.
Taken occasionally, they rarely cause kidney damage. If, however, they are taken over a long period of time or if they are taken when the kidneys are clearly damaged, they can lead to a progressive loss of kidney function. The problem is that this loss often only becomes noticeable when a large part of the kidney function has already been lost.
There are also drugs for which even a small amount of intake can lead to acute kidney damage. These include some antibiotics and some chemotherapeutic drugs. However, it is very different from person to person which drug causes damage to the kidneys and how quickly this happens.
In general, people who already have a damaged kidney should be extremely careful when choosing their medication. It is therefore essential that you contact your doctor before taking any new medication yourself. Chronic kidney failure, on the other hand, is usually caused by a long-standing underlying disease.
Chronic kidney failure is often the result of poorly controlled diabetes mellitus (diabetes) or untreated high blood pressure (hypertension). Both underlying diseases lead to slowly progressing damage to the kidney, which is no longer reversible after some time and leads to chronic kidney failure requiring dialysis. Especially patients with a combination of But also chronic inflammation of the kidney tissue, the regular intake of large amounts of different painkillers over years or tumor diseases of the kidney can trigger chronic kidney failure.
Patients with a previous acute kidney failure also have a significantly increased risk of developing chronic kidney failure. – high blood pressure,
- Diabetes mellitus,
- Lipometabolic disorder and
- Overweight (metabolic syndrome) have a significantly increased risk of chronic kidney failure. If an existing acute kidney failure has been diagnostically confirmed, the most urgent measure is the immediate compensation of the volume deficiency according to the cause of the loss (bleeding, fluid loss via the gastrointestinal tract, burns, etc.).
In addition, care should be taken to ensure a sufficient calorie intake (especially via glucose), especially if the patient is on dialysis. Drugs that should be discontinued now, as they can be dangerous, are dopamine, as well as loop and osmotic diuretics (water-removing drugs). Since the organism can now only tolerate fluid intake to a limited extent, the administration of hypertonic infusion solutions is necessary (supply of fats).
With appropriate laboratory values and clinical signs, renal replacement therapy is unavoidable. This should generally be started at the following signs: Hemodialysis / dialysis, hemofiltration and hemodiafiltration are available as options for renal replacement therapy. – Hyperkalemia (from 6.5 mmol/l) = too high blood potassium levels
- Urea > 180 – 200 mg/dl
- Creatinine > 8 mg/dl
- Uremic symptoms such as pericarditis (inflammation of the pericardium), nausea, encephalopathy (poisoning of the brain)
- Pulmonary edema, untreatable hypervolemia
- Severe hyperphosphatemia (too high a level of phosphate in the blood), especially with simultaneous hypercalcaemia (too much calcium in the blood)
The actual prognosis, i.e. only for the kidney, is quite good. The transition to chronic kidney failure is rare. The prognosis is even better if urination is maintained.
Acute kidney failure with causes such as circulatory disorders or toxins can have a phased course: The interval between each phase varies with time. Acute renal failure (AVN) can also be associated with numerous complications. The water and electrolyte balance (potassium, calcium) as well as the acid-base balance of the organism are severely disturbed by the drying up of urine excretion.
The fluid overload is manifested by oedema and hypertension (high blood pressure). Particularly dangerous in this context is the “fluid lung“, i.e. shortness of breath due to water (interstitial oedema) in the lungs, which can only be seen on an X-ray. Furthermore, hyperkalemia (high potassium levels in the blood) can occur, which is to be considered an emergency, as it can develop very quickly.
It is promoted by metabolic acidosis (acidification due to lack of H+ excretion via the kidneys) and can lead to severe cardiac arrhythmia from values of 7 mmol/l. Furthermore, it can lead to gastric ulcer (ulcus ventriculi) and duodenal ulcer (ulcus duodeni) and associated bleeding. – Oliguria/anuria (little or no urination)
- Polyuria (too much urination)
- Normalization of the renal function