• filter – removing waste and water from the blood (as urine, via the bladder)
• clean the blood
• keep the bones healthy
• look after blood pressure
• stimulate the bone marrow to make blood

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.

Symptoms of acute kidney injury

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:

• nausea and vomiting
• dehydration
• confusion
• high blood pressure
• abdominal pain
• slight backache
• a build-up of fluid in the body (oedema)

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.

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 heart failure, liver failure or 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:

• an enlarged prostate
• a tumor in the pelvis – such as an ovarian or bladder tumor
• kidney stones

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

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.

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.