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