Acute kidney injury, which used to be called acute renal failure, is the sudden decrease in kidney function. When acute kidney injury occurs, the kidneys have trouble removing waste products and excess fluids, which then build up in the body and upset the body's normal chemical balance.

The most common causes of acute kidney injury are serious infection, blood loss from major surgery or injury, or medicines such as non-steroidal anti-inflammatory drugs (NSAIDs), antibiotics, or the dyes (contrast agents) used in X-ray tests.

Symptoms depend on the cause of the problem and can include:

• Little or no urine output.
• Dizziness upon standing.
• Swelling, especially of the legs and feet.
• Loss of appetite, nausea, and vomiting.
• Feeling confused, anxious and restless, or sleepy.
• Pain in the flank, which is felt just below the rib cage and above the waist on one or both sides of the back.

The treatment of acute kidney injury includes finding the cause and correcting it. Treatment also includes following a special diet, taking certain medicines, and possibly doing dialysis. This will continue until the kidneys are functioning normally. Most people who develop acute kidney injury are already in the hospital.