What Is Acute Kidney Injury?

Treatment depends on the cause and severity of the condition, which can cause mild to complete kidney loss. In many cases, especially if treated early, AKI is reversible, with some people recovering complete kidney function.

There are three main types of acute kidney injury, depending on where the damage occurred:

• Prerenal AKI A condition that affects the blood vessels, such as dehydration or cardiovascular disease, prevents enough blood from reaching the kidneys.
• Renal AKI The kidneys have direct damage.
• Postrenal AKI An obstruction or pressure blocks the tubes that drain urine from the kidneys.

The signs and symptoms of acute kidney injury can vary depending on the individual and severity of the condition. Many people have no symptoms until the condition has progressed to a more severe stage.

• Making less urine than usual
• Swelling (edema) in your legs, ankles, or feet due to fluid buildup
• Fatigue
• Shortness of breath
• Nausea
• Loss of appetite
• Confusion
• Flank pain on the side of your back below your rib cage
• High blood pressure
• Chest pain or pressure
• Coma or seizures, when severe

People may also experience signs and symptoms of conditions or infections that cause AKI, such as very low blood pressure or sepsis.

The damage that leads to acute kidney injury has different causes.

Prerenal Acute Kidney Injury

• Dehydration
• Use of ACE inhibitors, angiotensin receptor blockers, and nonsteroidal anti-inflammatory drugs (NSAIDs) at high doses, particularly for people with preexisting kidney disease
• Blood loss
• Very low blood pressure
• Heart or liver failure

Renal Acute Kidney Injury

• Sepsis is a life-threatening immune response to infection and requires immediate treatment.
• Acute tubular necrosis is disorder that damages the tubule cells of the kidneys.
• Acute interstitial nephritis is a disorder in which the space between the tubule cells, or the interstitial tissue, become inflamed.
• Damage to the renal artery may include thrombosis, embolism, and stenosis.

These drugs tend to cause kidney damage only during specific circumstances, such as when combined with severe dehydration or when used with multiple nephrotoxins. Adjusting or stopping these medications entirely may reverse kidney damage, but this form of kidney disease cannot always be resolved easily, and some of the damage may be irreversible.

Postrenal Acute Kidney Injury

The ureters are the tubes that connect the kidneys to the bladder. Postrenal acute kidney injury occurs when urine cannot freely flow through these tubes, which can cause backflow into the kidneys. A person may not be able to urinate, which can cause the kidneys to swell and experience a number of issues, such as inflammation and scarring.

Risk Factors for Acute Kidney Injury

These risk factors can increase the hazard of developing acute kidney injury:

• Being 65 years and older
• Chronic kidney disease (CKD) or prior kidney surgery
• Chronic liver disease
• Congestive heart failure
• Diabetes
• Anemia
• Sepsis
• Peripheral vascular disease
• Renal artery stenosis
• High blood pressure
• High LDL (“bad”) cholesterol (hypercholesterolemia)
• Low albumin or low sodium levels
• Taking nephrotoxic medications

Doctors diagnose acute kidney injury by reviewing an individual’s medical history, doing a physical exam, and performing blood and urine tests. Typically, imaging or biopsies are only done in severe cases or when the cause is unknown.

• Medical History Reviewing a person’s medical history can help alert doctors to any medications that may be contributing or if past conditions may be the cause of AKI.
• Physical Examination In an exam, a doctor may be able to narrow down a diagnosis. For example, some people develop a skin rash due to an underlying condition, such as acute interstitial nephritis, or medications that can lead to acute kidney injury.

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• Urine Tests Making less urine is one of the most common symptoms of AKI, so a urine output test can be done to check how much urine is being produced. A doctor may also request a urine sample to test for electrolyte levels and signs of kidney functioning or an infection.
• Blood Tests A doctor may do a complete blood count to rule out other conditions. They may also conduct tests to measure the amount of waste products, such as creatinine, estimated glomerular filtration rate, urea nitrogen, sodium, potassium, and bicarbonate. Higher levels of these waste products can indicate that your kidneys are not functioning as they should.
• Other Tests A doctor may recommend an ultrasound of the kidneys if they suspect an obstruction. A biopsy of the kidneys is typically only performed when the cause of symptoms is unclear.

Treatment of acute kidney injury depends on the underlying cause. If kidney damage has been caused by an unrelated condition such as a kidney stone, prostate cancer, or heart failure, treating that condition will help the kidneys recover their ability to function.

Immediate treatments can include the following:

• Stopping nephrotoxic medications that can cause kidney damage
• Providing fluids and monitoring vitals, especially for people with dehydration
• Taking antibiotics, if AKI is caused by an infection
• Limiting sodium, phosphate, and potassium intake for some people, as these can be difficult for the kidneys to process
• Inserting a catheter, if AKI is caused by a blockage
• Undergoing dialysis, depending on damage to the kidneys
• Restricting water intake for some people

It’s not always possible to prevent acute kidney injury due to certain risk factors, such as age or being hospitalized. However, there are ways to support kidney health and prevent long-term damage:

• Get an annual physical. A yearly physical exam will include blood tests that can determine if the kidneys are healthy or not. It can also help a doctor identify any conditions that increase the risk of AKI early.
• Stay well hydrated. Dehydration can contribute to AKI, so it’s important to drink plenty of fluids. Aim to drink 1.5 to 2 liters of water every day, unless a doctor has advised otherwise. Drink more water if it’s a very hot day or you’re ill and have a temperature.

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• Seek help for diarrhea and vomiting. These symptoms can cause dehydration, which can increase your risk of AKI. It’s important to see a doctor as soon as you experience them to prevent developing AKI.
• Treat any underlying conditions. Treating an underlying condition like CKD can go a long way in preventing acute kidney injury. Managing CKD can include avoiding the use of NSAIDs, stopping smoking, and avoiding foods high in potassium and salt.

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• Avoid contrast for imaging when possible. If undergoing certain imaging tests, it’s important to discuss the pros and cons of an iodine contrast dye with a doctor. A doctor may advise against using this dye, as it can affect the kidneys.

It’s important to know if you have any risk factors for acute kidney injury, like CKD or diabetes. If you do, being aware of the symptoms of AKI can help you seek medical attention sooner.

• Follow up with your healthcare team regularly, especially about your kidney health.
• Eat foods with less potassium, like apples, carrots, green beans, and white rice. The kidneys are responsible for processing potassium, and with loss of function, they can have difficulty removing any excess. Too high levels can cause heart problems.

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• Limit foods with phosphorus. It can be found in dairy products, oatmeal, dark-colored sodas, and nuts. Your kidneys can have difficulty filtering out excess phosphorus, and too much in your blood can weaken bones.

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• Limit your salt intake to manage blood pressure by swapping out packaged foods, fast foods, snacks, and processed meats and cheeses. High blood pressure is a risk factor for AKI.

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• Stay hydrated to avoid dehydration and extra stress on your kidneys.

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The outlook for an individual with AKI depends on the underlying cause and severity of kidney damage.

Taking care of your overall kidney health and seeking immediate treatment when experiencing any signs or symptoms can aid in your recovery and may help reverse any damage.

• Permanent Kidney Damage In some cases, acute kidney injury may lead to end-stage kidney disease, though this depends on the underlying cause and your kidney function prior to the diagnosis. People with end-stage kidney disease will need dialysis or a kidney transplant.
• Fluid Buildup If fluid builds up in the lungs, it can cause shortness of breath and other lung and breathing issues.
• High Potassium and Phosphate Levels Too much potassium can lead to arrhythmias, while phosphate can cause bone and joint pain.

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• Chest Pain This symptom may occur if the lining of the heart (pericardium) becomes inflamed. Other cardiovascular conditions can also arise, such as arrhythmias and cardiac arrest, though these are rare.
• Muscle Weakness The kidneys are responsible for regulating electrolyte concentrations in the body. Electrolyte imbalances can cause muscle weakness.
• Gastrointestinal Bleeding People may also experience stomach bleeding if the cause of acute kidney injury is related to taking medications like NSAIDs.

In severe cases, such as if the kidneys stop working entirely, acute kidney injury may be fatal.

Disparities exist in the mortality rates, outcomes, and treatment of acute kidney injury.

CKD is often associated with acute kidney injury. Any condition that puts stress on the kidneys may contribute to this condition, including electrolyte imbalances, kidney disease, and cancer.

• High blood pressure
• Diabetes
• Atrial fibrillation
• Heart disease or heart failure
• Electrolyte, fluid, and acid-base disorders
• Liver disease

National Kidney Foundation

You can learn detailed information on keeping your kidneys healthy, kidney conditions and their treatments, and kidney transplants. You can find support through a free information helpline, communities, or peer-mentoring groups. The foundation also offers a way for people to get involved in kidney research.

American Kidney Fund

This charity organization offers support in many forms. It provides information, a space to donate, disaster relief, help with insurance premiums, grants and scholarships, and more. It also has a resource finder to connect you with assistance in your community.

• Acute kidney injury results in the kidneys having a decreased ability to filter out waste products. It can be caused by damage to the kidneys or by obstruction in the blood vessels or the urinary system connected to the kidneys.
• People may not always experience symptoms with acute kidney injury. But if they do, one symptom is producing less urine than usual.
• Acute kidney injury is often reversible, especially when its cause is identified quickly.