Condition Basics

What is acute kidney injury?

Acute kidney injury (which used to be called acute renal failure) means that your kidneys have suddenly stopped working normally. Your kidneys remove waste products and help balance water and salt and other minerals (electrolytes) in your blood. When your kidneys stop working, waste products, fluids, and electrolytes build up in your body. This can cause problems that can be deadly.

What causes it?

Acute kidney injury has three main causes:

• A sudden, serious drop in blood flow to the kidneys. Heavy blood loss, an injury, or a bad infection called sepsis can reduce blood flow to the kidneys. Not enough fluid in the body (dehydration) also can harm the kidneys.
• Damage from some poisons, infections, and medicines such as ibuprofen. People who have serious, long-term health problems, such as chronic kidney disease, are more likely to have a kidney problem from medicines. Injury can also be caused by many different diseases, including lupus and scleroderma.
• A sudden blockage that stops urine from flowing out of the kidneys. Kidney stones, a tumour, an injury, or an enlarged prostate gland can cause a blockage.

Risk factors

You have a greater chance of getting acute kidney injury if:

• You are an older adult.
• You have a long-term health problem such as kidney or liver disease, diabetes, high blood pressure, heart failure, or obesity.
• You are already very ill and are in the hospital or intensive care (ICU). Heart or belly surgery or a bone marrow transplant can make you more likely to have kidney problems.

What are the symptoms?

Symptoms of acute kidney injury may include:

• Little or no urine when you try to urinate.
• Swelling, especially in your legs and feet.
• Not feeling like eating.
• Nausea and vomiting.
• Feeling confused, anxious and restless, or sleepy.
• Pain in the back just below the rib cage. This is called flank pain.

Some people may not have any symptoms. And for people who are already quite ill, the problem that's causing the kidney injury may be causing other symptoms.

How is it diagnosed?

Acute kidney injury is most often diagnosed during a hospital stay for another cause. If you are already in the hospital, tests done for other problems may find your kidney problem.

If you're not in the hospital but have symptoms of kidney injury, your doctor will ask about your symptoms, what medicines you take, and what tests you have had. Your symptoms can help point to the cause of your kidney problem.

Blood and urine tests can check how well your kidneys are working. A chemistry screen can show if you have normal levels of sodium (salt), potassium, and calcium. You may also have an ultrasound. This imaging test lets your doctor see a picture of your kidneys.

How is acute kidney injury treated?

Your doctor or a kidney specialist (nephrologist) will try to treat the problem that is causing your kidney injury. Treatment can vary widely, depending on the cause. For example, your doctor may need to restore blood flow to the kidneys, stop any medicines that may be causing the problem, or remove or bypass a blockage in the urinary tract.

At the same time, the doctor will try to:

• Stop wastes from building up in your body. You may have dialysis. This treatment does the work of your kidneys until they recover. It will help you feel better.
• Prevent other problems. You may take antibiotics to prevent or treat infections. You also may take other medicines to get rid of extra fluid and keep your body's minerals in balance.

You can help yourself heal by taking your medicines as your doctor tells you to. You also may need to follow a special diet to keep your kidneys from working too hard. You may need to limit sodium, potassium, and phosphorus. A dietitian can help you plan meals.

Does it cause lasting problems?

Doctors sometimes can fix the problems that cause kidney injury. The treatment takes a few days or weeks. These people's kidneys will work well enough for them to live normal lives.

But other people may have permanent kidney damage that leads to chronic kidney disease. A small number of them will need to have regular dialysis or a kidney transplant. Older people and those who are very sick from other health problems may not get better. People who die usually do so because of the health problem that caused their kidneys to fail.