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Patient education: Acute kidney injury (The Basics)
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Patient education: Acute kidney injury (The Basics)
Written by the doctors and editors at UpToDate
All topics are updated as new evidence becomes available and our peer review process is complete.
Literature review current through: Sep 2017. | This topic last updated: May 30, 2017.

What is acute kidney injury? — Acute kidney injury is when the kidneys suddenly stop working. Normally, the kidneys filter the blood and remove waste and excess salt and water (figure 1). The word "acute" means sudden.

Another term for acute kidney injury is "acute kidney failure."

What causes acute kidney injury? — Acute kidney injury can have different causes. It can happen when:

Less blood than usual flows to the kidneys. Different things can cause this to happen. For example, in a condition called heart failure, the heart might not be able to pump enough blood to the kidneys.

The kidneys get damaged. Some causes of kidney damage are infections, cancer, certain medicines, and some autoimmune conditions. In an autoimmune condition, a person's infection-fighting system attacks his or her body.

The path the urine takes to leave the body is blocked. Some causes of blockages are prostate problems (in men) and cancer.

What are the symptoms of acute kidney injury? — Some people do not have any symptoms at first. People who are in the hospital might learn that they have acute kidney injury after they have blood tests for another reason.

When people do have symptoms, the symptoms can include:

Urinating less, or not urinating at all

Blood in the urine, or urine that is red or brown

Swelling, especially in the legs or feet

Vomiting, or not feeling hungry

Feeling weak, or getting tired easily

Acting confused, or not acting like themselves

Seizures – Seizures are waves of abnormal electrical activity in the brain. They can make people pass out, or move or behave strangely.

Should I call my doctor or nurse? — Call your doctor or nurse if you have any of the above symptoms. If you are already in the hospital, let your doctor or nurse know if you have any of these symptoms.

Is there a test for acute kidney injury? — Yes. Your doctor will ask about your symptoms and do an exam. To check how well your kidneys are working, he or she will do blood and urine tests.

Most people will have an imaging test called an ultrasound to look for blockages in the urinary system. Imaging tests can create pictures of the inside of the body.

Your doctor might do other tests to look for other causes of your acute kidney injury. These can include X-rays or other imaging tests of your belly or kidneys.

If these tests don't show what's causing your acute kidney injury, your doctor might do a test called a biopsy. For a biopsy, the doctor will put a needle into your back and into your kidney. He or she will remove a tiny sample of tissue. Then another doctor will look at the sample under a microscope.

How is acute kidney injury treated? — Treatment depends on what's causing your acute kidney injury and how severe the kidney injury is.

If your acute kidney injury is caused by a medicine, your doctor will have you stop taking that medicine. Plus, to help your kidneys heal, he or she might also give you medicines called steroids. (These steroids are different from the ones athletes take to build muscle.)

If your acute kidney injury has another cause that can be treated, your doctor will treat it. For example, doctors can treat infections with antibiotics.

Most of the time, a person's kidneys will heal and work normally again. But it can take weeks to months for the kidneys to heal completely.

Until your kidneys can work normally again, you might need treatments to help make sure your body has the right amount of fluid, salt, and nutrients. These treatments can include:

Medicines

Changes in your diet

Renal replacement therapy – This treatment takes over the job of your kidneys until they can heal. It involves either:

Hemodialysis – Hemodialysis is a procedure in which a machine takes over the job of the kidneys. The machine pumps blood out of the body, filters it, and returns it to the body (figure 2). People have hemodialysis at least three times a week.

Peritoneal dialysis – Peritoneal dialysis is a procedure that people do at home every day. It involves piping a special fluid into the belly. This fluid collects waste and excess salt and water from the blood. Then the used fluid drains out of the belly (figure 3).

More on this topic

Patient education: Blood in the urine (hematuria) in adults (The Basics)
Patient education: Swelling (The Basics)
Patient education: Hemodialysis (The Basics)
Patient education: Peritoneal dialysis (The Basics)
Patient education: Dialysis and diet (The Basics)
Patient education: Chronic kidney disease (The Basics)
Patient education: Rhabdomyolysis (The Basics)
Patient education: Glomerular disease (The Basics)

Patient education: Peritoneal dialysis (Beyond the Basics)
Patient education: Hemodialysis (Beyond the Basics)
Patient education: Chronic kidney disease (Beyond the Basics)

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All topics are updated as new information becomes available. Our peer review process typically takes one to six weeks depending on the issue.