Acute renal failure is the sudden loss of kidney function. When acute renal failure occurs, the kidneys are unable to remove 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 renal failure are dehydration, blood loss from major surgery or injury, or medicines such as nonsteroidal 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 on one side of the back, just below the rib cage and above the waist (flank pain).

The treatment of acute renal failure includes correcting the cause and supporting the kidneys with dialysis until proper functioning is restored. Most people who develop acute renal failure are already in the hospital.