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 taking certain medicines, includingdiuretics; diuretics are usually beneficial to the kidneys, but may become less helpful when a person is dehydrated or suffering from a severe illness
you're given aminoglycosides– a type of antibiotic; again, this is only an issue if the person is dehydrated or ill, and these are usually only given in a hospital setting
AKI is estimated to affect 13-18% of people admitted to hospital. It can affect both adults and children.
Causes of acute kidney injury
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:
low blood volume after bleeding, excessive vomiting or diarrhoea, or as seen with severe dehydration
the heart pumping out less blood than normal as a result of sepsis, for example
problems with the blood vessels – such as inflammation and blockage in the blood vessels within the kidneys (a rare condition called vasculitis)
certain medicines (see above), which can affect the blood supply to the kidney – other medicines may cause unusual reactions in the kidney itself
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:
symptoms or signs of a disease affecting the kidneys and other organs
Diagnosing acute kidney injury
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:
blood creatinine level has risen from the baseline value for that person (by 26 micromoles per litre or more within 48 hours)
blood creatinine level has risen over time (by 50% or more within the past 7 days)
they are passing much less urine (less than 0.5ml per kg per hour for more than 6 hours)
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.
any medication that's been taken in the past week – as some medicines can cause AKI
An ultrasound scan should reveal if the cause is a blockage in the urinary system, such as an enlarged prostate or bladder tumour.
Treating acute kidney injury
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:
advise stopping any medication that may be causing the situation, or making it worse – it may be safe to resume some of these when the problem is sorted
treat any underlying infections
advise on fluid intake to prevent dehydration (which could cause or worsen AKI)
take blood tests to monitor levels of creatinine and salt – to check how well a person is recovering
refer to a urologist (genitourinary surgeon) or nephrologist (kidney specialist) if the cause isn't clear or if a more serious cause is suspected
Admission to hospital is necessary in cases where:
there's an underlying cause that needs urgent treatment – such as a urinary blockage, or if the person is seriously unwell; most people need hospital care to treat the underlying cause, allowing the AKI to get better
there's a risk of urinary blockage – because of prostate disease, for example
the person's condition has deteriorated, and regular blood and urine tests are needed to monitor how well their kidneys are working
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 dialysis–where a machine filters the blood to rid the body of harmful waste, extra salt and water – may be needed.
Preventing acute kidney injury
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.