Acute kidney injury (AKI) symptoms, treatment and prevention

What is acute kidney injury (AKI)?

Acute kidney injury (AKI), also known as acute renal failure, happens when your kidneys suddenly stop working the way they should. This can cause waste to build up in your blood and lead to serious health problems if not treated quickly. AKI usually develops quickly, usually within hours or a few days, and needs immediate medical attention.

AKI is serious and needs to be treated right away to prevent lasting kidney damage. If AKI is treated early, most people will return to their previous kidney function. If you were healthy before AKI and you got treated right away, your kidneys could work normally or almost normally after treatment.

AKI can sometimes lead to chronic kidney disease (CKD). In time, CKD can cause your kidneys to stop working altogether. This is known as kidney failure, end-stage renal disease (ESRD), or end-stage kidney disease (ESKD).

Who is at risk for AKI?

Anyone can develop AKI, but some people are at higher risk, especially those who are already hospitalized or critically ill. AKI is most common in people staying in intensive care units (ICUs), where complex health issues like infection, surgery, or low blood pressure can suddenly impact kidney function. Studies show that up to 50% of ICU patients may develop some level of AKI. 

You have a higher chance of AKI if you:   

• Have had major surgery, including cardiac surgery like a coronary artery bypass
• Were in the hospital for COVID-19 (coronavirus)
• Are age 65 or older
• Have heart disease, congestive heart failure or COPD (chronic obstructive pulmonary disease)   
• Have a history of kidney disease
• Have severe, uncontrolled high blood pressure
• Take insulin for diabetes
• Have peripheral artery disease (a condition that makes it hard for your blood to get to your arms and legs)
• Are severely dehydrated or unable to keep fluids in your body

What are the symptoms of AKI?

AKI can be hard to spot at first. Your doctor may find it during routine tests, even if you feel fine.

In more severe forms of AKI, signs and symptoms may include:

• Urinating (peeing) less often
• Edema (swelling) in legs or feet
• Feeling weak and tired
• Shortness of breath
• Confusion
• Nausea and loss of appetite
• Feeling pain or pressure in your chest
• Seizures or coma (in severe cases of AKI)
• High blood pressure
• Pain on the sides of your back, chest pain or pressure

When to see a doctor

Talk to your doctor if you notice a combination of any of these symptoms. Even mild or early signs of acute kidney injury can get worse quickly without treatment. Detecting AKI early gives your care team the best chance to reverse the damage, preventing long-term kidney problems and avoiding complications like fluid overload, electrolyte imbalance, or the need for dialysis. The sooner you get diagnosed, the more likely you will fully recover.

How is AKI diagnosed?

Some of the most common tests used to check for AKI include:

• Serum creatinine: A blood test that measures the amount of creatinine in your blood. It tells how well your kidneys are working. When they're not working well, your serum creatinine level goes up.
• eGFR (estimated glomerular filtration rate): This blood test measures how well your kidneys are working. Your eGFR is an estimated number that is calculated based on measuring creatinine, a waste product filtered by the kidneys, along with your age and sex.
• BUN (blood urea nitrogen): Your blood urea nitrogen (BUN) level is based on a test that measures the amount of urea nitrogen in your blood. Urea nitrogen is a waste product that your body makes after it breaks down protein. Healthy kidneys take urea nitrogen out of your blood. When your kidneys are not working well, your BUN level goes up. 

Other blood tests may be ordered, such as check your sodium, potassium, and bicarbonate levels (to see if anything is out of balance).

• Urine output: While in the hospital, your healthcare professional may track how much urine (pee) you pass each day.
• Urine test (urinalysis): A general urine test may be used to understand if there is blood, protein, or other abnormalities in the urine.
• Imaging tests, like an ultrasound, may be helpful in some cases to check if stones or clots may be affecting kidney function.

What causes acute kidney injury?

AKI usually happens when another illness or condition suddenly reduces blood flow to the kidneys, directly damages them, or blocks urine flow. These causes are grouped into three main categories:

There is not enough blood flow to your kidneys ("prerenal AKI")

Some conditions can restrict blood flow to your kidneys, including:

• Low blood pressure (can be due to infection, dehydration, heart disease, or other conditions)
• Severe bleeding
• Severe diarrhea
• Heart disease or heart attack
• Sepsis, when your body has a dangerous reaction to an infection
• Liver failure
• Using NSAIDs (nonsteroidal anti-inflammatory drugs), such as aspirin, ibuprofen, or naproxen, than the label recommends.
• Severe burns
• Severe dehydration (not having enough water in your body)
• Severe allergic reaction

There is direct damage to your kidneys (intrarenal AKI)

These conditions cause inflammation (swelling) or damage inside the kidneys, including:

• Blood clots in your kidneys
• Diseases that affect the kidneys, such as glomerulonephritis and lupus nephritis
• Infections, such as hepatitis C, polyoma virus, and HIV
• Medicines, such as:
  • Certain chemotherapy drugs
  • Some antibiotics
  • Contrast dyes used in CT scans, MRIs, and other imaging tests
• Alcohol or drug abuse
• Some blood or blood vessel disorders, such as vasculitis 

There is a blockage in your urinary tract (postrenal AKI)

AKI can happen if urine can't leave the body and backs up (also known as reflux) into the kidneys. This can be caused by:

• Certain cancers, such as lymphoma and leukemia
• Blood clots in or around the kidney vessels
• Kidney stones
• Bladder problems
• Enlarged prostate

How do doctors treat AKI?

AKI treatment depends on what caused it and how severe it is. Some people need to be treated in a hospital and stay until their kidneys heal. Possible treatments include:

• Medicines to control your blood pressure and adjust the electrolytes in your blood
• Treatments to keep the right amount of fluid in your body (e.g. diuretics to make you pee out extra fluid)
• If the AKI is severe and your kidneys completely stop working, going on dialysis for a short period of time. Dialysis will do the work that your kidneys should do until they recover.
• When you return home, follow a kidney-friendly eating plan to help your kidneys heal. Your doctor may refer you to a registered dietitian.

Even after treatment, some people may not fully recover kidney function. AKI can increase your risk for chronic kidney disease (CKD) or make existing CKD worse. Your doctor may recommend long-term follow-up testing to monitor kidney health and help you avoid further complications.

How can I prevent AKI? 

It can be hard to predict or prevent AKI. But a healthy lifestyle and taking good care of your kidneys can help. If you have any of these conditions, talk to your doctor about how you can prevent AKI.

Ask your healthcare provider if the cause of your AKI is preventable and what you can do to keep it from happening again. Also, ask when you need to follow up to check your kidney function.