What is acute kidney injury?

Kidney problems can develop suddenly (acute) or over the long term (chronic). Many conditions, diseases, and medicines can create situations that lead to acute and chronic kidney problems. Acute kidney injury, which used to be called acute renal failure, is more commonly reversible than chronic kidney failure.

• Acute kidney injury (AKI) is usually caused by an event that leads to kidney malfunction. Common causes include serious infection, blood loss from major surgery or injury, or the use of some medicines.
• Chronic kidney disease (CKD) is usually caused by a long-term disease, such as high blood pressure or diabetes, that slowly damages the kidneys and reduces their function over time.

The presence or lack of symptoms may help your doctor determine whether acute kidney injury or chronic kidney disease is present.

• Symptoms of decreased kidney function, such as fluid buildup or electrolyte imbalance, are more likely to develop with acute kidney injury, regardless of how long the kidney has been malfunctioning. Symptoms may reflect the actual cause of the kidney problem.
  • An obstruction in the urinary tract may cause pain in the side or lower back (flank pain), blood in the urine, or reduced urine output.
  • Dehydration may cause extreme thirst; lightheadedness or faintness; a weak, rapid pulse; and other symptoms.
• Symptoms of chronic kidney disease may not develop until very little kidney function remains. Other problems may develop with chronic kidney disease, such as anemia and increased levels of phosphorus in the blood (hyperphosphatemia), along with complications caused by kidney failure. These complications often do not develop until kidney disease has been present for some time.

Most cases of acute kidney injury occur in people who are already in the hospital for other reasons. In these people, acute kidney injury is usually diagnosed when routine tests show a sudden increase in creatinine and blood urea nitrogen (BUN) levels. A buildup of these waste products in the blood points to a decrease in kidney function. Your doctor will compare these levels to previous tests to find out if your kidney problem is acute or chronic.

An ultrasound of the kidneys also may help determine whether kidney problems are acute or chronic. Normal-sized kidneys may be present in either condition, but when both kidneys are smaller than normal, chronic kidney disease is usually the problem.

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.

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.

Treatment depends on the cause of the kidney injury. For example, your doctor may restore blood flow to the kidneys, stop certain medicines, or fix a urinary blockage. You may have dialysis. It does the work of your kidneys until they recover. You may take medicines, like antibiotics, and follow a special diet.

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.

• Talk to your doctor about how much fluid your child should drink.
• Be sure your child eats a healthy diet. Talk to your doctor or a dietitian about what type of diet may be best for your child. Your child may need to limit sodium, potassium, and phosphorus.
• If your child needs dialysis, follow the instructions and schedule for dialysis that your doctor gives you.
• Be safe with medicines. Read and follow all instructions on the label. Review all of your child's medicines with your doctor. Do not give your child any medicines, including nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (Advil, Motrin), unless your doctor says it is safe to do so.
• Make sure that anyone who treats your child for any health problem knows that your child has a history of acute kidney injury.

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.

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.

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 tumor, an injury, or an enlarged prostate gland can cause a blockage.