Acute Kidney Injury (AKI)

Acute kidney injury (AKI) is a term used to describe when your kidneys are suddenly not able to filter waste products from the blood. This can happen within a few hours or a few days. For most people, AKI develops within 48 hours, but sometimes it can take as long as 7 days.

This replaces an older term “acute renal failure” (or ARF) which you may still see or hear occasionally.

The signs and symptoms of AKI can differ depending on many factors like the cause, severity, and your other health conditions. If symptoms do happen, they may include one or more of the following:

• Making less urine (pee) than usual or no urine
• Swelling in legs, ankles, and/or feet
• Fatigue or tiredness
• Shortness of breath (trouble breathing)
• Confusion or mood changes
• High blood pressure
• Decreased appetite (low desire to eat)
• Nausea
• Flank pain (pain on the side of your back - between your ribs and hips)
• Chest pain or pressure
• Seizures or coma (in severe cases)

In some cases, AKI causes no symptoms and is only found through other tests done by your healthcare professional.

AKI can have many different causes. Many people get AKI when a related disease or condition puts extra stress on your kidneys. Another common cause for AKI is when your body is reacting to an urgent or emergent health concern (such as heart surgery or COVID-19 infection). Lastly, AKI can be caused by medications or other substances that you may consume. Examples for each of these scenarios are provided below.

Usually, AKI happens because of a combination of factors. This is especially true for older adults who are at higher risk given their age.

AKI can cause a build-up of waste products in your blood and make it hard to keep the right balance of fluid and minerals in your body. It can also cause permanent damage to your kidneys, leading to chronic kidney disease (CKD). Without treatment, AKI can also affect other organs such as the brain, heart, and lungs. So, it is important to know what to watch for and how to lower your risk.

If your healthcare professional suspects AKI, they will perform an assessment to identify its potential cause (or causes). This may include performing a physical exam, reviewing your medical conditions and medication use history in the past week (including over-the-counter products and herbal supplements), asking about recent events and experiences (e.g. symptoms, water intake, recreational drug use, relevant travel), and ordering blood and/or urine tests.

Tests

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

• Serum (blood) creatinine – a blood test used to check how well your kidneys are filtering this waste product from your blood
• Estimated glomerular filtration rate (eGFR) – this is calculated based on your serum (blood) creatinine level, age, and sex to estimate your kidney function
• Blood urea nitrogen (BUN) – similar to creatinine, this test can be used to measure another waste product in your blood to see how well your kidneys are filtering the blood
• Other blood tests, such as sodium, potassium, and bicarbonate (to see if anything is out of balance)
• Urine output – your healthcare professional may track how much urine (pee) you pass each day, especially if you are having AKI in the hospital
• Urine test (urinalysis) – a general urine test may be used to find more clues about the cause of AKI
• Imaging tests, like an ultrasound, may be helpful in some cases
• Kidney biopsy – in some less common situations, your healthcare professional may need to look at a tiny piece of your kidney under a microscope to get a better idea about the cause

Treatment for AKI depends on what caused it in the first place. This is why finding the cause is so important. Some most common approaches to treating AKI include:

• Stopping any medicines that may be causing or contributing to your AKI
• Giving you fluids (either by mouth or through your veins)
• Antibiotics (if AKI is caused by a bacterial infection)
• Placing a urine catheter (a thin tube used to drain your bladder, useful if AKI is caused by a blockage)
• Dialysis (depending on the severity of damage to your kidney and/or impact on your other organs)
  • In most cases, dialysis treatments are only temporary until the kidneys can recover.

Most people with AKI will need to spend some time in the hospital to be monitored while receiving treatment.

After having AKI, you have a higher risk for other health problems, such as chronic kidney disease (CKD), heart disease, or stroke). You are also at a higher risk of getting AKI again in the future. So, it is important to have regular follow-up visits with your healthcare professional and check your kidney health, starting with two simple tests (ideally within 3 months of finishing treatment for your AKI).

Questions to ask

• What are my biggest risk factors for AKI?
• What can I do to help lower my risk for AKI?
• Are there any medications I should avoid (either now or in the future) due to my kidneys?
• [If having potential symptoms of AKI] Should I go to the emergency room for my symptoms?
• Was the cause of my AKI preventable? If so, what can I do to prevent it from happening again?
• When should I follow up after my AKI treatment is done to check my kidney health?

This content is provided for informational use only and is not intended as medical advice or as a substitute for the medical advice of a healthcare professional.