Acute kidney failure (acute renal insufficiency) is characterized by the sudden loss of kidney function. This usually occurs within a few days. Initially, acute kidney failure is asymptomatic. In later stages, there is reduced urine output, high blood pressure, water retention and shortness of breath. Despite the minor symptoms, you should not underestimate this serious illness.
Below you will find further information and selected specialists for acute kidney failure.
The kidneys are one of the smallest organs in the body. At the same time, however, they are the organs with the highest blood flow in resting mode and under physical stress. The kidneys have a variety of functions in the human organism (Figure 1). Doctors and patients usually underestimate the importance of the kidneys.
Figure 1: Functions of the kidneys in the human organism
Acute kidney failure can occur when the kidneys are in the best of health (acute) or when kidney disease is known(acute chronic).
In contrast to chronic kidney failure, acute kidney failure is characterized by the sudden loss of kidney function. The deterioration in kidney function usually occurs within a few days.
The incidence of acute renal failure has been increasing for 7 years .
This applies to both hospital-acquired forms (by far the largest group) and community-acquired cases. Acute and chronic renal failure is one of the most common causes of long-term dialysis in the USA.
There are many different causes. The following classification has been established:
Any serious organ disease or circulatory disorder of the kidney can lead to kidney failure. The most common causes are blood loss, dehydration and shock. Severe heart or liver disease can also lead to kidney failure.
Another common cause of acute kidney failure is previous contrast medium examinations. The number of unreported cases of renal failure following cardiac catheterization is high. However, as the increase in creatinine only occurs 24 to 48 hours after the administration of the contrast medium, the patients have already left the hospital.
Approximately 1 percent of patients who previously had a healthy kidney require dialysis treatment after a cardiac catheterization . Renal failure increases the hospital mortality rate of heart patients from 1 percent to 36 percent. 13 to 50 percent of patients who require dialysis after contrast medium administration remain permanently on dialysis.
In addition to pain, blood pressure and water medication, the following diseases can cause renal insufficiency:
Acute kidney failure initially presents without symptoms, which is why doctors and patients often do not notice it. Urine excretion is often maintained.
Only when the kidneys have stopped functioning to 90 percent does a reduction in urine excretion occur. High blood pressure, water retention and shortness of breath also occur.
Kidney poisoning, which used to be fatal, manifests itself in non-specific symptoms such as
In the early stages, the doctor can only recognize acute kidney failure by measuring kidney function. To do this, he measures the serum creatinine in the blood and then converts it into kidney function (glomerular filtration rate GFR) (diagram 2).
The conversion is necessary because serum creatinine is dependent on gender, age, muscle mass, food intake and amount drunk.
However, it does not show the current renal situation if the creatinine has not had enough time to accumulate in the body. The serum creatinine is then low, although the kidney function is already significantly reduced.
Even on dialysis, kidney function can no longer be measured by serum creatinine, as dialysis removes the creatinine.
Figure 2: Kidney function can most often be calculated using the creatinine measured in the blood. There is a quadratic relationship between creatinine and kidney function. Therefore, even small increases in serum creatinine (e.g. 0.3 mg/dl) can contribute to a large loss of renal function (e.g. 50 %).
There are different stages of acute kidney failure (Figure 3).
Figure 3: Classification of the stages of acute kidney failure.
In addition to taking a blood sample , doctors carry out a urine test and an ultrasound examination of the kidneys for diagnosis. The sonography rules out chronic or post-renal kidney failure.
In rare cases, a duplex examination of the kidneys confirms a circulatory disorder. Computed tomography enables the diagnosis of a renal artery embolism.
If the cause of the acute kidney failure cannot be clarified, a kidney biopsy must be performed. Ideally, doctors should carry this out on the day of admission.
The treatment of acute renal failure includes a range of measures such as
In the short term, high potassium levels can lead to cardiac arrest. Doctors must therefore take dietary measures to stop the intake of potassium (fruit juices and fruit).
The patient must avoidpotassium-containing medication or potassium-sparing, diuretics . If necessary, doctors will use a potassium binder.
There is also a risk of overhydration, which leads to shortness of breath. However, as underhydration also leads to further damage to the kidneys, the intake of salt and fluids must be balanced. The amount of fluid intake depends on the amount of urine and the invisible loss of fluid through the skin.
In the case of renal insufficiency, doctors must reduce the dosage of all water-soluble medication excreted via the kidneys. If this is not done, they accumulate in the blood and cause side effects and poisoning.
Doctors usually discontinue ACE inhibitors, AT1 blockers and non-steroidal anti-inflammatory drugs (painkillers) in cases of acute kidney failure, as they contribute to further deterioration. Contrast medium examinations are also taboo.
If there is a critical increase in renal toxins, doctors will carry out renal replacement therapy. This is carried out by means of hemodialysis. In acute kidney failure, early dialysis initiation (urea 150 mg/dl) and more intensive dialysis (daily dialysis) bring significant survival benefits.
Dialysis site for hemodialysis @ Tyler Olson /AdobeStock
Acute kidney failure is a serious disease that patients and doctors often underestimate. Before the introduction of dialysis in 1960, the mortality rate was almost 100 percent.
Today, it is 40 to 70 percent for intensive care patients with acute renal failure. Kidney function usually recovers within 1 to 3 weeks.
Short-term prognosis:
Until a few years ago, doctors believed that once kidney failure had been overcome and kidney function was normal, everything would be fine again. However, various studies have shown that the prognosis after kidney failure is not as good as assumed.
Patients who have already required dialysis have a 28-fold higher risk of developing chronic renal failure requiring dialysis.
Long-term prognosis:
Acute kidney failure not only has consequences for the kidney. Despite recovery of the kidney, it leads to increased mortality in the further course of the disease.
It appears that the kidney remembers the acute kidney failure. Afterwards, nothing is the same as before, even if the creatinine is within the normal range.
Specialists are needed to care for patients with acute renal failure .
Studies have shown that a nephrologist should be involved as early as possible in order to avert acute renal failure. If renal failure does occur, the severity is less pronounced and the mortality rate is lower.
