Acute renal failure develops rapidly over a few hours or days. It may be fatal. It's most common in those who are critically ill and already hospitalised.Symptoms includes decreased urinary output, swelling due to fluid retention, nausea, fatigue and shortness of breath. Sometimes symptoms may be subtle or may not appear at all. In addition to addressing the underlying cause, treatments include fluids, medication and dialysis. Acute kidney injury (AKI) is a sudden episode of kidney failure or kidney damage that happens within a few hours or a few days. AKI causes a build-up of waste products in your blood and makes it hard for your kidneys to keep the right balance of fluid in your body.