Fact sheet Patient conditions

Published on 1 Jul 2015

Acute kidney failure

What is acute kidney failure?

Acute kidney failure, also called acute renal failure, is when the kidneys suddenly stop working properly. This can happen, for example, when there is a sudden loss of large amounts of blood, or as a result of an infection.

When the kidneys stop working, the fluids and chemicals in the body can rise or fall to abnormal levels and cause problems ranging from swelling of the legs, to difficulty breathing.

What do the kidneys do?

There are two kidneys, one on either side of the spine, above the waist. They play a vital role in the daily workings of our body. They:

  • filter out waste products from the blood
  • help keep various chemicals in the blood at the right level
  • help control blood pressure
  • make a hormone called erythropoietin, which stimulates the bone marrow to make red blood cells.

What causes acute kidney failure?

The kidneys need good blood flow to work properly. There are many things that can cause the kidneys to stop working properly. Losing a large amount of blood, due to an injury, can mean the kidneys stop working properly. So can severe burns, sepsis or a big heart attack.

Damage to the kidneys themselves can also be the cause. For example due to a medical condition like lupus, or when toxic drugs are taken. A blockage of the outflow of urine from the kidneys via the bladder, such as due to an enlarged prostate or kidney stones, can also cause acute kidney failure.

What are the symptoms of acute kidney failure?

The symptoms of acute kidney failure tend to be general symptoms that can have many different causes. They can include:

  • drowsiness and fatigue
  • loss of appetite
  • confusion
  • muscle cramps and weakness
  • nausea and vomiting
  • reduced urine output
  • swelling of the feet and ankles.

How is acute kidney failure diagnosed?

Usually, the most important clue that the kidneys are not working properly is a reduction in the amount of urine being produced. Doctors can measure this accurately by inserting a tube called a catheter into the bladder. Blood tests can also show if waste products are not being cleared properly by the kidneys. Other blood and urine tests or imaging tests, such as ultrasound or x-ray, are often required to understand why the kidneys are failing.

How is acute kidney failure treated?

The most effective way to treat acute kidney failure is to find and treat its cause. For example, removing a kidney stone, or transfusing blood. Once the cause is identified and treated, kidneys that used to be healthy will often start working again in a matter of days. However, if there was existing damage to the kidneys, it may take longer to recover.

If the kidneys have failed completely and a life-threatening level of fluids or toxins has built up in the body, treatment with an artificial kidney machine may be needed. This is known as dialysis. Dialysis works to filter the blood and help with fluid balance in the body. To do this ICU patients will have a large catheter, sometimes referred to as a ‘vascath’, inserted into a large vein in the upper chest or groin.

Recovery after treatment

In most cases, if the kidneys were healthy before acute kidney failure, they will be able to recover fully after treatment. The younger a person is, the more likely their kidneys will completely recover.

Occasionally the kidney damage becomes permanent, despite the underlying cause being successfully treated. If the damage is very severe, long-term dialysis or a kidney transplant may be required.

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