Acute Kidney Failure
Acute kidney failure must be handled as an emergent medical situation. While in chronic renal failure, kidney functions deteriorate slowly, the situation progresses rapidly in the acute failure.
The causes of acute renal failure can be divided into three main groups.
This category includes mainly circulatory disorders. The primary problem is not within the kidneys, but in disruption of renal blood supply (blood, oxygen, nutrients) resulting in damage of the kidney tissue. The most common causative factor is simple dehydration. Especially the elderly people have generally decreased feeling of thirst and their kidneys have lower reserves. The treatment is easy – the patient must be carefully rehydrated and the kidney functions usually rapidly improve. In addition, acute kidney failure may accompany conditions associated drop of the blood pressure such as the acute heart failure and shock states.
In this case, the acute kidney failure is associated with a primary disease or damage of the kidney tissue. It includes the damage caused by toxic substances (heavy metals), medications (some antibiotics, diuretics) and contrast agents used in radiology. Kidney tubules may also get clogged by myoglobin molecules during a process known as the rhabdomyolysis (occurring for example in the so-called crush syndrome) or by deposits of pathological protein molecules in multiple myeloma. Sudden kidney failure may accompany certain glomerulonephritides.
This group of causes is related to impaired urine flow and its accumulation in the kidneys. The situation is usually caused by an obstruction of the urinary tract (urinary stones, enlarged prostate, urinary tract tumors, etc.). The accumulation of urine just below the kidneys is called hydronephrosis. It can compress the kidney tissue and damage it permanently. The situation should be solved by an emergent urological intervention aimed at removing the obstruction or perform the so-called nephrostomy.
The primary manifestation of sudden kidney damage is decreased production of urine and accumulation of fluids in the body. The patient is threatened by disruption of the internal environment of the body, accumulation of potassium (hyperkalemia), nitrogenous metabolic waste products and metabolic acidosis. The situation may manifests with impaired consciousness, cardiac arrhythmias, coma and eventually death. If the person survives this phase (usually due to acute dialysis), the kidney tissue regenerates. However, the newly created renal tubular cells have not the ability to concentrate urine and to prevent the fluid loss. This phase is referred to as polyuric and it is characterized by inadequately high loss of water and ions. The patient urinates many liters of fluid a day and we have to cautiously prevent him from dehydration.
We can check the so-called renal parameters. These parameters include the serum concentration of urea and creatinine. Lowered filtration capacity causes increase of both urea and creatinine. We should always also check the serum level of minerals (especially potassium) and parameters of acid-base homeostasis. It is very advisable to perform at least ultrasound examination of the abdominal cavity to exclude hydronephrosis.
The therapy depends on the type of kidney damage (see Causes). Prerenal situation must be solved by rehydration or stabilization of the circulatory system. In renal causes, it is necessary to solve the causes of kidney tissue damage and ensure adequate hydration. Cases of postrenal failure must be treated by ensuring the urine outflow. Any case of acute kidney failure directly threatening the life of patient must be followed by acute dialysis. The dialysis helps to survive the acute period and when the kidneys regenerate, it is no longer needed. However, when the damage is irreparable, chronic dialysis must be performed.