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Acute kidney injury (AKI) is sudden damage to the kidneys that causes them to not work properly. It can range from minor loss of kidney function to complete kidney failure.
AKI normally happens as a complication of another serious illness. It's not the result of a physical blow to the kidneys, as the name might suggest.
This type of kidney damage is usually seen in older people who are unwell with other conditions and the kidneys are also affected. Read more about who's at risk of AKI.
It's essential that AKI is detected early and treated promptly. The role of the kidneys is to:
Without quick treatment, abnormal levels of salts and chemicals can build up in the body, which affects the ability of other organs to work properly.
If the kidneys shut down completely, this may require temporary support from a dialysis machine, or lead to death.
In the early stages of AKI, there may not be any symptoms. The only possible warning sign may be that the person isn't producing much urine, although this isn't always the case.
However, someone with AKI can deteriorate quickly and suddenly experience any of the following:
Even if it doesn't progress to complete kidney failure, AKI needs to be taken seriously. It has an effect on the whole body, changes how some drugs are handled by the body and could make some existing illnesses more serious.
AKI is different to chronic kidney disease, where the kidneys gradually lose function over a long period of time.
You're more likely to get AKI if:
AKI is estimated to affect 13-18% of people admitted to hospital. It can affect both adults and children.
Most cases of AKI are caused by reduced blood flow to the kidneys, usually in someone who is already unwell with another health condition.
This reduced blood flow could be caused by:
AKI can also be caused by a problem with the kidney itself, such as glomerulonephritis. This may be caused by a reaction to some drugs, infections or contrast medium (the liquid dye used in some types of X-rays).
It may also be due to a blockage affecting the drainage of the kidneys, such as:
A doctor may suspect AKI in people known to be at risk who suddenly fall ill or develop symptoms which suggest complications of AKI.
AKI may also be suspected in people who have been unwell for a while and have either:
AKI can be diagnosed after measuring urine output and doing blood tests.
Blood levels of creatinine – a chemical waste product produced by the muscles – will be measured. Healthy kidneys filter creatinine and other waste products from the blood and these are excreted, in the form of urine. It's an easy and quick marker of kidney function, with higher levels of creatinine in the blood indicating poorer kidney function.
In adults, a diagnosis of AKI can be made if:
In children and teenagers, doctors should use the plasma creatinine level to calculate the estimated glomerular filtration rate (estimated glomerular filtration rate (eGFR). A diagnosis of AKI is made if they have a 25% or greater fall in eGFR within the past 7 days.
Read more about AKI in children.
Urine can be tested for protein, blood cells, sugar and waste products, which may give clues to the underlying cause.
Doctors also need to know about:
An ultrasound scan should reveal if the cause is a blockage in the urinary system, such as an enlarged prostate or bladder tumour.
Treatment of AKI depends on the underlying cause and extent of illness. In most cases, treating the underlying problem will cure the AKI.
GPs may be able to manage mild cases in people who aren't already in hospital. They may:
Admission to hospital is necessary in cases where:
The majority of people who recover from AKI end up with a very similar level of kidney function as they had before they became ill, or go on to have normal kidney function.
However, some people go on to develop chronic kidney disease or long-term kidney failure as a result. In severe cases, dialysis – where a machine filters the blood to rid the body of harmful waste, extra salt and water – may be needed.
Those at risk of AKI should be monitored with regular blood tests if they become unwell or start new medication. It's also useful to check how much urine you're passing.
Any warning signs of AKI, such as vomiting or producing little urine, require immediate investigation for AKI and treatment. People who are dehydrated, or at risk of dehydration, may need to be given fluids via a drip.
Any medicine that seems to be making the problem worse, or directly damaging the kidneys needs to be stopped, at least temporarily.
The National Institute for Health and Care Excellence (NICE) has produced detailed guidelines on preventing, detecting and managing AKI.
The most serious complications of acute kidney injury are: