What Is Acute Kidney Injury (AKI)?
Acute kidney injury (AKI) — also known as acute kidney failure — is when your kidneys stop working suddenly. It can happen over just a few hours or days.
Acute kidney injury isn’t always permanent. If you get treatment right away — and if you don’t have other serious health problems — your kidneys can go back to working normally.
The main job of your kidneys is to filter waste out of your blood. They also remove extra fluid from your blood (which becomes urine) and control blood pressure. Kidneys help make red blood cells. They regulate electrolytes (a type of mineral) and activate vitamin D, too.
Kidneys don’t work well when they’re damaged. This could happen because of another health condition, such as diabetes.
Acute kidney injury vs. chronic kidney disease
While acute kidney injury happens all of a sudden, a decrease in kidney function that happens over a longer period is called chronic kidney disease (CKD). The most common causes of CKD are long-term conditions, such as diabetes or high blood pressure (hypertension).
The symptoms you have (or don’t have) will help your doctor find out which kidney condition you have. Acute kidney injury involves a sudden decline in the how your kidneys work, which could be reversed. On the other hand, the symptoms of chronic kidney disease may not appear until there’s only a bit of kidney function left. It can be permanent.
An ultrasound can confirm whether your kidney condition is acute or chronic. Kidney size can look normal for ultrasounds of both acute and chronic kidney conditions. But if the size of both of your kidneys is smaller, it’s usually chronic kidney disease.
Acute Kidney Injury Stages
The stages of kidney disease are determined by your estimated glomerular filtration rate (eGFR), which is a measure of your kidney’s ability to filter.
An eGFR close to 100 is considered normal. Zero is the lowest eGFR, and this rate happens when you have no kidney function left.
Your GFR corresponds to the percentage of kidney function. The kidney disease stages include:
Stage I (GFR 90 or higher). Your kidneys still work normally, but you may have mild damage.
Stage II (GFR 89 to 60). Your kidney function loss is mild, and your kidneys still work well.
Stage IIIa (GFR 59 to 45. The loss of kidney function may be mild to moderate.
Stage IIIb (GFR 44 to 30). Your kidney function loss is moderate to severe.
Stage IV (GFR 29 to 15). You have a severe loss of kidney function.
Stage V (GFR lower than 15). Your kidneys are close to or at complete failure.
Acute Kidney Injury Symptoms
You may not have any symptoms of acute kidney injury. Your doctor may discover you have this condition while doing lab tests for another reason.
If you do have symptoms, they’ll depend on how bad your loss of kidney function is, how quickly you lose kidney function, and the reasons for your kidney failure. Symptoms may include:
- Peeing less than normal
- Swelling in your legs, ankles, and feet (caused by your body holding on to fluid)
- Feeling drowsy or very tired
- Shortness of breath
- Itching
- Joint pain and swelling
- Loss of appetite
- Confusion
- Throwing up or feeling like you’re going to
- Chest pain or pressure
- Muscle twitching
- Seizures or coma (in severe cases)
- Stomach and back pain
- Fever
- Rash
- Nosebleed
3 Acute Kidney Injury Causes
There are three main reasons your kidneys fail all of a sudden.
1. Something is changing the way blood flows through to your kidneys.
It could be because of:
- An infection
- Liver failure
- Medications (aspirin, ibuprofen, naproxen, or COX-2 inhibitors such as Celebrex)
- Blood pressure medications
- Heart failure
- Serious burns or dehydration
- Blood or fluid loss
2. You have a condition that’s blocking urine from leaving your kidneys.
This could mean:
- Bladder, cervical, colon, or prostate cancer
- Blood clots in your urinary tract
- An enlarged prostate
- Kidney stones
- Nerve damage in your bladder
3. Something has directly damaged your kidneys.
This could happen due to:
- Blood clots
- Cholesterol deposits
- Medications that can directly damage kidneys, including nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and naproxen, chemotherapy, and antibiotics
Glomerulonephritis, a condition where your kidney filters are inflamed, can also hurt your kidneys. This can be caused by an infection, autoimmune disease (such as lupus, vasculitis, and scleroderma), multiple myeloma, chemotherapy drugs, antibiotics, or other toxins.
Acute Kidney Injury Risk Factors
Most of the time, kidney injury happens along with another medical condition or event. You may have a greater chance of acute kidney injury if you:
- Have been hospitalized for a long time, especially in intensive care
- Have diabetes
- Are an older adult
- Have coronary artery disease (CAD)
- Have heart failure or high blood pressure
- Have chronic kidney or liver disease
- Have cancer
Acute Kidney Failure Diagnosis
Your doctor will start with a physical exam. Then, they’ll order tests of your blood, urine, and kidneys.
Blood tests. These measure substances in your blood.
Urine tests. Your doctor will check your pee for blood and protein. They’ll also look for certain electrolytes. The results help your doctor understand what’s causing your kidney injury.
Kidney biopsy (renal biopsy). A kidney biopsy is a procedure where the doctor pushes a thin needle through your skin and takes a small piece of your kidney to look at under a microscope. It can show if there’s any damage or disease in your kidney and often helps determine the cause as well. This is typically done only in cases where it’s unclear what’s causing the kidney injury.
Imaging tests. Some tests, such as ultrasonography or a CT scan, can show whether your kidneys are enlarged or there’s a blockage in your urine flow. They can also tell your doctor if there is any problem with arteries or veins going in and out of your kidneys. An MRI can show this, too.
Kidney Injury Treatment
Often, treatment for acute kidney injury, especially if severe, requires hospitalization. If there aren’t any other problems, the kidneys may heal themselves.
In most other cases, acute kidney injury can be treated if it’s caught early. It may involve changes to your diet, the use of medications, IV fluids, relief of anything that's blocking kidneys, or even dialysis (if kidney injury is severe).
Diet. Your doctor may adjust the amount of salt and potassium you get based on your electrolyte levels. Changing how and what you eat won’t reverse acute kidney injury. But your doctor may change your diet while they treat the conditions that caused it. This may mean treating a health problem such as heart failure, taking you off certain medications, or giving you fluids through an IV if you’re dehydrated. If your doctor has put you on a low-potassium diet, you’ll need to cut back on high-potassium foods such as bananas, spinach, oranges, potatoes, and tomatoes. On the other hand, you can eat more low-potassium foods such as apples, strawberries, grapes, and cauliflower.
Medications. Your doctor may prescribe medicines that regulate the amount of fluid, phosphorus, and potassium in your blood, as these can be thrown off when the kidneys aren’t working properly. There may also be additional medications given, depending on the cause. For example, medications that suppress the immune system are used if there’s an autoimmune condition such as glomerulonephritis.
Dialysis. If your kidney damage is severe enough, you may require hemodialysis until your kidneys can heal. Dialysis doesn’t help kidneys heal but takes over the work of kidneys until they do. If your kidneys don’t heal, dialysis could be long-term.
Acute Kidney Injury Complications
Acute kidney failure can sometimes cause complications. These include:
Fluid buildup. Acute kidney injury can sometimes cause a buildup of fluid in your body. If fluid builds up in your lungs, this can cause shortness of breath.
Toxin buildup. This can lead to confusion, nausea, fatigue, and other symptoms.
Chest pain. If the lining that covers your heart becomes inflamed, you may have chest pain.
Acidic blood (metabolic acidosis). If your blood has too much acid due to acute kidney failure, you can end up with nausea, vomiting, drowsiness, and breathlessness.
Muscle weakness. When your body’s fluids and electrolytes are out of balance, you can get muscle weakness. In serious cases, this can lead to paralysis and heart rhythm problems.
Permanent kidney damage. Acute kidney injury can become chronic, and your kidneys will stop working almost completely. This is called end-stage renal disease. If this happens, you will need to go on permanent dialysis (to filter your blood and remove toxins) or get a kidney transplant.
Death. Acute kidney injury can lead to severe loss of kidney function, which can cause death.
Acute Kidney Failure Prevention
You can reduce your risk of getting acute kidney failure by practicing some healthy habits.
Be careful when taking over-the-counter (OTC) pain medications. Whether you are taking NSAIDs such as aspirin, ibuprofen, and naproxen or other types of OTC pain medications such as acetaminophen, it’s important to read and follow the recommended dosing instructions on the package. If you take too much of these medications, you could increase your chances of getting acute kidney injury.
Follow your doctor’s advice. If you have a higher risk of getting acute kidney injury because of preexisting kidney disease or other conditions, make sure to follow your doctor's advice for treating and managing your condition.
Keep a healthy lifestyle. Exercise, eating nutritious food, and keeping a good body weight can go a long way in preventing acute kidney injury.
Takeaways
Your kidneys play an important role, as they filter out waste from your blood. When acute kidney injury happens, higher levels of waste can build up and chemicals in your blood can be unbalanced. This type of kidney injury happens quickly, but it can be reversed with treatment. If you have symptoms such as decreases in how often you pee, tiredness, irregular heartbeat, or swelling in the lower part of your body, talk to your doctor immediately or get emergency treatment.
Acute Kidney Injury FAQs
Here are some of the most commonly asked questions about acute kidney injury.
Can kidneys recover from acute injury?
Yes. If treated soon enough, kidney damage from acute kidney failure can be reversed. Treatment includes finding out the cause and preventing complications while your kidneys heal.
How long does it take for acute kidney injury to develop?
Acute kidney injury can develop in less than a few days.