Acute kidney failure

Acute kidney failure: description

The term “acute kidney failure” (acute renal insufficiency or renal insufficiency) stands for the sudden, sharp drop in kidney detoxification within hours to days. The so-called glomerular filtration rate (GFR) decreases acutely. And this also reduces the volume of fluid that is filtered in the kidney per unit of time. Affected are the so-called glomeruli – fibrocartilage in the kidney, which act as tiny filters.

An acute renal failure has the consequence that substances accumulate in the blood that should actually be excreted in the urine. These so-called urinary substances include urea and creatinine. Their accumulation in the body leads to a gradual urine poisoning. Doctors speak of uremia.

Acute renal failure: four stages

In most cases, acute renal failure occurs in four stages:

• Damage phase (initial phase): It takes a few hours to days.
• Oligo- or anuric phase: At this stage, the urine secretion goes back significantly, until only little (oligurie) or practically no urine (anuria) leaves the body. This phase generally lasts ten days.
• Recovery phase: When the kidneys recover, they produce more and more urine (up to five liters and more a day). This phase lasts about three weeks.
• Recovery phase: Now, the kidney cells are more or less functional again, but a complete healing of the disease is not always possible. This last stage can take up to two years.

Acute kidney failure: mortal danger

Every year about 50 out of every 1 million people develop acute renal insufficiency. It is more common in intensive care patients. Up to 25 percent of them have acute kidney failure. It must be treated quickly medically, otherwise there is danger to life. In principle, acute renal failure – in contrast to chronic renal failure – is reversible. That is, the kidney can recover from an almost complete acute loss of function.

Acute kidney failure: symptoms

What symptoms can cause acute renal insufficiency, read in the article Kidney Failure – Symptoms.

Acute kidney failure: causes and risk factors

Depending on the cause, acute renal failure is divided into the following forms:

Pre-renal failure

Pre-renal failure is due to decreased renal blood flow. The most common cause of this is blood and fluid loss from major surgery or accidents. Changes in renal blood flow through certain medications (X-ray contrast agents, ACE inhibitors, or antibiotics) can also cause prerenal kidney failure. In rare cases, heart failure (heart failure) or blood poisoning (sepsis) is the cause of reduced renal blood flow and thus of acute renal failure.

Renal renal failure

Renal-related acute renal failure is triggered by direct damage to kidney tissue. Such damage is caused for example by inflammation, such as non-bacterial nephritis (glomerulonephritis) or vasculitis. Also, kidney infections with bacteria (pyelonephritis) or viruses (interstitial nephritis) as well as toxic substances (such as certain antibiotics) can damage the kidneys and thereby trigger acute kidney failure.

Postrenal kidney failure

The cause of postrenal kidney failure is obstruction of urinary output. For example, kidney stones, tumors and prostate enlargement can disrupt the urine drainage and thus cause acute kidney failure.

Acute kidney failure: examinations and diagnosis

In order to diagnose acute renal failure and to investigate the possible cause, the doctor will record the medical history of the patient (anamnesis) and perform various examinations:

blood test

Renal values ​​(creatinine and urea) typically increase in the blood during acute renal failure. Even more meaningful is creatinine clearance. It indicates how fast the kidneys can remove creatinine from the blood. Kidney damage is reduced at an early stage. In addition, there are changes in blood salts, especially an increase in potassium levels. Also, the blood count and other blood values ​​(such as liver enzymes, C-reactive protein, etc.) can provide important evidence of acute renal failure.

Urinalysis

Very important for the diagnosis of “acute renal failure” is the detection of protein in the urine, which is normally or hardly to be found there. In addition, the glomerular filtration rate (GFR), the amount of urine, the specific gravity and the salt content of the urine are determined among other things.

ultrasound

Ultrasound examination (sonography) of the kidneys and the urinary tract is routine in examining a patient for acute renal failure. If there is a postrenal kidney failure, the causative disorder of urinary outflow (such as through a kidney stone) can be detected by ultrasound.

In some cases, further investigation may be needed to determine the cause of acute kidney failure, such as x-ray examination of the kidney or removal of a tissue sample (renal biopsy).

Acute kidney failure: treatment

Acute kidney failure is treated in different ways – depending on the cause behind it. If, for example, kidney stones are responsible for acute renal failure by obstructing urinary outflow, they must be removed. Bacterial infections are treated with antibiotics, dosing drugs are reduced or stopped altogether, and high blood and fluid losses (such as accidents) are compensated by infusions.

The administration of fluid in the form of infusions is generally important in the period in which the kidneys recover from the insufficiency. If acute kidney failure has (almost) completely paralyzed the production of urine, diuretics are also administered. If these measures do not improve kidney function, the blood is artificially cleaned (dialysis) through a blood wash until the kidneys can resume blood purification and excretion alone.

Acute kidney failure: prevention

During and after major surgery, blood volume, blood pressure and fluid balance are closely monitored to reduce the risk of acute kidney failure.

Many medications can cause kidney damage, causing acute kidney failure. These include over-the-counter preparations such as certain analgesics (for example, acetaminophen, ibuprofen, diclofenac). Therefore, you should discuss any drug application with the doctor. This is especially true for patients with existing kidney disease and impaired kidney function – they are particularly prone to acute kidney failure.

Acute kidney failure: disease progression and prognosis

Acute kidney failure is a life-threatening condition. Acute renal insufficiency is particularly common in intensive care patients – mortality is 50 to 80 percent.

Becomes a acute kidney failure treated in time and the patient is not very weakened by other pre-existing conditions, the kidney function can also recover. Only in a few cases does the kidney function worsen slowly in the further course.