If you had renal failure, which organ wouldn't be working correctly?

Acute renal failure (also called acute kidney injury) means that your kidneys have suddenly stopped working. They 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 renal failure has three main causes:

• A sudden, serious drop in blood flow to the kidneys
• Damage from some medicines, poisons, or infections
• A sudden blockage that stops urine from flowing out of the kidneys.