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What is acute kidney injury?

Sometimes people’s kidneys can suddenly develop problems. This is known medically as acute kidney injury (AKI) – a sudden upset to the kidney, which is not necessarily a physical injury.

AKI can cause partial or complete loss of kidney function which can be temporary or longer lasting.

 

Causes of acute kidney injury

AKI can be caused by:

  • reduced blood supply to the kidney caused by bleeding, heart failure, infections and dehydration – for example, after an accident, an operation or a bout of sickness and diarrhoea which prevents someone eating and drinking properly
  • damage to the small blood vessels inside the kidney caused by:
    • blood clots, often from the heart in patients with an irregular heart rate (atrial fibrillation), which enter the kidney and stop blood circulating through the vessels
    • fragments of cholesterol-rich plaque from diseased arteries which break off and enter the kidney, stopping blood supply to the vessels
  • blockages which cause ‘back-pressure’ in the tubing systems that connect the kidneys to the bladder – for example, blockages in the ureter (the tube which urine passes through from the kidney to the bladder), or in the bladder outlet, caused by an enlarged prostate gland
  • high doses of ‘contrast’ used during X-rays, particularly when injected directly into the arteries, as in coronary angiography
  • problems within the kidneys themselves, such as glomerulonephritis, vasculitis (inflammation of the blood vessels), or kidney damage caused by drugs or toxins.

AKI can also be made worse by certain drugs including:

  • those which reduce the blood supply to the kidneys, including non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, naproxen and diclofenac
  • drugs used to treat high blood pressure.

It’s important to tell your doctor about the medications you’ve been taking and whether you’ve had a recent illness, accident or operation. This can help them to investigate if you have developed AKI.

Acute kidney injury symptoms

The most obvious sign of AKI is a reduction in the amount of urine a person passes, especially if this coincides with a bout of severe illness or a recent operation or accident. However, not all forms of AKI cause this - some patients with severe AKI (particularly those caused by back pressure) can continue to pass normal amounts of urine.

Acute kidney injury diagnosis

Doctors can diagnose AKI and assess the level of injury in several ways. These include:

  • Measuring creatinine levels in your blood. Creatinine is a waste product which can only be removed from the body by the kidneys - the creatinine level in the blood goes up when kidneys are working less efficiently
  • Measuring urine output per hour
  • Testing your urine to look for signs of infection, kidney inflammation, protein or blood in the urine (which can indicate kidney damage)
  • Using an ultrasound scan to look for signs of back pressure in the collecting systems, and to check kidney size and condition
  • Carrying out a kidney biopsy (a medical procedure where doctors take small samples of the kidney to look at under the microscope).

Acute kidney injury treatment

Depending on your level of kidney injury you may be:

  • Closely monitored to check the amount of fluids entering and leaving your body
  • Given additional fluids, often via a drip, if you are short of fluid
  • Given medication to treat or prevent infections and taken off certain drugs (such as ibuprofen) until your kidney function improves, or given alternatives
  • Given treatments to relieve any blockages
  • Put on dialysis to do the work of the kidneys in removing waste products, until the kidneys improve.

Risk of permanent damage

For many people, AKI is mild and causes no lasting kidney problems – especially if they are generally healthy. But others may be left with a long term reduction in kidney function, which is known as chronic kidney disease. Chronic kidney disease can also develop two to three years after an episode of AKI.

Very occasionally, a small proportion of people with AKI don't recover their kidney function and end up with end-stage kidney disease (ESKD).

Help for you

Don’t hesitate to speak to your GP if you have any concerns about acute kidney injury.

Read more about AKI.

Acute kidney injury – information from Edinburgh Renal Unit.

Understanding Acute Kidney Injury – a leaflet produced by Kidney Care UK .

Reviewed April 2019

Dr Tanya Smith
Dr Tanya Smith

"It is my hope that this opportunity will enable me to use exciting new technologies to transform kidney treatments.”

Dr Tanya Smith

Researcher spotlight

Dr Tanya Smith from Cardiff University has been awarded a clicnical training fellowship to investigate acute kidney injury (AKI) by studying the female kidney.

Tanya will be using an exciting new technique called ‘single cell sequencing’ to discover how individual cells respond to injury, and which types of cell might be especially important for recovery from AKI. Tanya hopes to provide new insights into how to avoid progression to CKD and kidney failure in AKI patients.  

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