Acute kidney failure is a life-threatening emergency that requires therapy as soon as possible. Read about the vital functions our kidneys perform and what symptoms indicate kidney failure. You will also learn everything important about diagnosis, therapy and prevention of acute kidney failure.

Synonyms

Acute renal failure, acute kidney failure, ANV

Definition

Renal failure examination

If the kidneys no longer perform their work, or only do so incompletely, doctors speak of kidney failure. A distinction is made between two types of course: acute renal failure (ANV) and chronic renal failure (CNI). Acute kidney failure develops within hours to days and usually heals without cause after the cause has been eliminated. With chronic renal failure, the disease progresses slowly over months to years and leads to death if left untreated.

Function of the kidneys

Healthy people have two kidneys, one on the left and one on the right. Both kidneys perform important tasks in the body:

  • Elimination of metabolic end products (so-called urinary substances) and medication
  • Keeping the water balance constant
  • Regulation of the electrolyte balance
  • Maintaining the acid-base balance
  • Formation of hormones (such as erythropoietin and renin)
  • Conversion of inactive to active vitamin D.
  • Blood pressure regulation.

The kidneys as an excretory organ

Around 1500 liters of blood flow through the kidneys every day. They excrete about one and a half liters of urine a day, which is filtered out of the blood. The blood flows through special filter systems (nephrons). A healthy kidney contains about 1 million such nephrons. In these filters, substances that the body no longer needs are sifted out of the blood, so to speak (so-called urinary substances). If the urinary substances remain in the blood, they poison the body. On the other hand, the nephrons also retain important substances in the body. These primarily include proteins and electrolytes.

Symptoms

The symptoms of acute kidney failure are different. The main symptom is in any case the significantly reduced amount of urine that is excreted. Sometimes water can no longer be left. In the course of the decreasing urine production, the water overflow of the body increases. The result is, for example, water retention in the legs (edema) and in the lungs (pulmonary edema). Furthermore, life-threatening electrolyte disturbances (e.g. increased blood-potassium concentrations) and life-threatening acidosis ( acidosis ) can occur. These make z. B. in the form of irregular heartbeat , nausea and vomiting as well as rapid fatigue noticeable. If fluid accumulates in the brain, the behavior of the patient can change. Indicative then are psychological abnormalities such as excessive fatigue , listlessness up to impaired consciousness.

Causes

The causes of acute kidney failure are classified by doctors as follows:

  • Prerenal ANV: In a maximum of 60 percent of cases, the cause of kidney failure lies in front of the kidney (i.e., pre-renally). Often this is a sudden, greatly reduced blood flow to the kidneys, for example due to circulatory shock in the event of an accident or surgery, due to blood clots in the renal arteries or due to drug side effects.
  • Intrarenal or renal ANV: Here the cause lies in the kidney itself (i.e. intra-renal). The triggers are damaged kidney tubules due to long-term lack of oxygen, damage by medication or contrast agents and rarely due to severe inflammation of the kidney function bodies (so-called glomerulonephritis).
  • Postrenal ANV: The cause is a drainage of the urine behind the kidney (i.e. post-renal). Above all, an enlarged prostate, kidney, bladder or urinary tract stones, inflammation or tumors hinder urine drainage.

Examination

To diagnose acute kidney failure, the doctor must first clarify whether it is acute kidney failure or chronic kidney failure. The ANV is easier to recognize: the lack of urine production quickly gives the decisive indication.

Other diagnostic methods include anamnesis (i.e. questioning the patient), the physical examination with listening to the heart and lungs, and laboratory tests. The urinary substances such as creatinine and urea in particular are determined in the blood. Test strips help with the urine examination. They record proteins, red and white blood cells, nitrite as an indication of a urinary tract infection, urine pH, glucose, ketone bodies and bile pigments. This is followed by an examination of the urine in the laboratory.

Ultrasound (sonography) and a color Doppler sonography of the kidneys as well as X-rays of the chest with heart and lungs are used as imaging methods. If the cause is inflammatory, a kidney biopsy may follow. In this examination, a tissue sample is taken from the kidney during an endoscopic procedure.

Treatment

The treatment of acute kidney failure depends primarily on the cause. The main steps are:

  • Compensate for lack of fluids (if necessary via infusions)
  • raise low blood pressure (if necessary, medication)
  • Discontinue or switch to medications (such as antibiotics, pain relievers and X-ray contrast media) that have led to acute kidney failure
  • Surgically remove urine drainage obstructions (e.g. bladder or urethral stones, enlarged prostate, tumors).

Medical therapy

If you have acute kidney failure, your doctor can try to stimulate the excretion function with medication. So-called loop diuretics such as furosemide, piretanide and torasemide are primarily administered for this purpose. Alternatively, dehydrating agents of the thiazide type such as hydrochlorothiazide and xipamide or potassium-sparing active ingredients such as spironolactone can also be used.

Dialysis

If the kidney function cannot be stimulated again with medication, the phase until the kidneys produce their own urine must be bridged with a kidney replacement procedure (dialysis).

Transplantation

Sometimes drug therapy and dialysis are not enough to restore or replace kidney function to a sufficient extent. In these rare cases, a kidney transplant may be necessary.

Forecast

The chances of a cure are very good if the cause of the acute kidney failure is not the kidney itself. This is the case with prerenal and postrenal renal insufficiency.

Intrarenal acute renal insufficiency is much less treatable, since in this form more or less kidney tissue has been lost to varying degrees and irretrievably. Acute intrarenal forms often result in chronic renal failure. In addition, the complication rate (mandatory dialysis) is significantly higher.

In many cases, serious illnesses, accidents or poisoning (also from medication) are the cause of acute kidney failure. In these cases, up to 50 percent of those affected do not survive. The main reason for this is not kidney failure, but the fact that caused this failure.

Prevention

Many over-the-counter medications can damage the kidneys and lead to acute kidney failure. Examples include popular over-the-counter medications such as the pain relievers diclofenac, ibuprofen and paracetamol or gastric acid inhibitors from the group of proton pump inhibitors. Therefore, you should not take painkillers in particular longer than recommended. In principle, it is advisable to coordinate any prolonged use of medication with a doctor.

Gastric acid blockers pose risks

Proton pump inhibitors such as esomeprazole, lansoprazole, omeprazole, pantoprazole and rabeprazole are among the best-selling drugs in Germany. According to the drug report of the Barmer health insurance, almost 12 million German proton pump inhibitors were prescribed in 2018. In addition, the active substances omeprazole, pantoprazole or esomeprazole are also available over the counter. In the public perception, gastric acid blockers from the proton pump inhibitor group of active substances are considered a simple and safe drug. However, 2 aspects are left out: the side effects and the fact that proton pump inhibitors can make you addicted.

Kidney damage as a side effect

The most common side effects of proton pump inhibitors include bone loss (osteoporosis) and magnesium deficiency with an increased risk of irregular heartbeat and seizures. These side effects have now been proven by a whole series of studies. Sometimes even more serious is the fact that the drugs permanently disrupt the natural control cycle of gastric acid production. After prolonged use, between 14 and 64 percent of the patients remain permanently dependent on the medication.

Connection of proton pump inhibitors and allergies possible

Proton pump inhibitors may increase the risk of allergic diseases. Scientists from the University of Vienna published a study in the specialist journal “Nature Communications” (August 2019) (see sources) that establishes at least one striking statistical connection between the long-term use of proton pump inhibitors and allergic diseases. The scientists had evaluated data from Austrian health insurance companies. In doing so, they found that the likelihood of prescribing antiallergic drugs increased by up to 300 percent if gastric acid blockers were previously prescribed. This does not necessarily mean that proton pump inhibitors actually trigger or promote allergies.

The German Society for Gastroenterology, Digestive and Metabolic Diseases rates the study result differently. According to the press release, the specialist society sees no “evident connection between gastric acid blockers and allergies”. The design of the Austrian study does not give a corresponding assessment.

Study location

Study on proton pump inhibitors and allergy: Country-wide medical records infer increased allergy risk of gastric acid inhibition: https://www.nature.com/articles/s41467-019-10914-6

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