Acute kidney injury

You have 2 kidneys, 1 on each side of your body just under your ribcage on either side of your spine (backbone). As your blood circulates around your body it goes through your kidneys and is filtered to remove waste. Your kidneys turns this waste and excess fluid into urine (pee). 

Their main function is to remove waste products from your body and to balance your body's fluid. However, your kidneys also perform other tasks related to hormones, making red blood cells and filtering out medicines. Read more about how your kidneys work. 

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Acute kidney injury (AKI) means that your kidneys have suddenly stopped working as well as they used to. This might have happened in the past few hours, days or rarely weeks.

• Acute kidney injury affects both your kidneys and can range from minor loss of kidney function to complete kidney failure.
• If it's not picked up in time, your kidneys can deteriorate quite quickly and shut down. This can lead to permanent damage and can be life threatening if not detected within hours and treated quickly. 
• AKI is not the same as chronic kidney disease (CKD), in which your kidneys lose their function gradually over a long period of time.
• CKD often goes unnoticed until your kidney function is significantly impaired and doesn't get better with time. Read more about chronic kidney disease.

AKI can happen at any age, but it's more common in older people and in people who are in hospital for surgery or an acute medical problem (eg, heart failure or liver failure).

You are at increased risk of AKI if you:

• have an existing kidney problem, eg, chronic kidney disease or nephritis
• have a long-term condition, eg, heart failure, liver disease or diabetes
• are dehydrated, eg, when you have diarrhoea, vomiting, or 'gastro' (a tummy bug)
• have an infection – particularly an infections of your kidneys
• have a blockage of one or both of the tubes leading from your kidneys to your bladder (eg, kidney stones), bladder cancer or an enlarged prostate 
• are taking some medicines, especially if you take them while you're unwell.

Medicines and acute kidney injury

Taking some medicines increases your risk of getting AKI, especially if you take these medicines while you are dehydrated, or you take a combination of these medicines.

Examples of medicines that increase your risk of AKI

• non-steroidal anti-inflammatory medicines (ibuprofen, diclofenac)
• lithium
• ACE inhibitors (cilazapril, enalapril, lisinopril, quinapril)
• ARBs (losartan, candesartan)
• diuretics (furosemide, spironolactone)
• glibenclamide, gliclazide, glipizide
• metformin
• proton pump inhibitors (omeprazole, lansoprazole, pantoprazole)
• some antibiotics
• dyes used in some X-ray tests

Read more about how you can protect your kidneys.

The most common signs and symptoms are:

• passing less urine (pee/mimi) than usual
• passing very clear, dilute urine – more than usual
• loss of appetite
• feeling sick (nausea) or vomiting
• feeling tired and short of breath
• feeling confused, anxious and restless, or sleepy
• swelling of your legs or other parts of your body 
• pain in your abdomen or middle back.

Sometimes AKI can occur without any signs and symptoms and can only be picked up by a blood test and/or urine test.

AKI is usually diagnosed from a blood test that measures the level of a substance called creatinine in your blood. Creatinine is a normal by-product of your muscle function and high levels of creatinine mean that your kidneys are not getting rid of waste products as well as they should. Sometimes a sample of urine will be checked for blood and protein (dipstick test) and an ultrasound scan of the kidneys will be done to pick up any blockages. 

In rare cases, a kidney biopsy may be needed to work out what is causing AKI. This involves taking a very small sample of tissue from one kidney using a fine needle. The area will be numbed using local anaesthetic.

After AKI you can make a full recovery and have normal kidney function or you can make a partial recovery with lower levels of kidney function. Some people may have permanent kidney damage that requires dialysis.

After AKI your kidney function can continue to recover over time. People who have a history of AKI have a higher risk of chronic kidney disease. It's recommended that you get your kidney function checked out by your healthcare provider every year for the first 3 years following an AKI.