What is renal failure, and what does it have to do with kidney disease?

Kidney disease causes renal failure. Renal failure, or kidney failure, means that the kidneys can no longer function well enough to filter waste and excess fluid out of the bloodstream. In acute kidney disease cases, the sudden development of renal failure may heal, but chronic kidney diseases gradually decrease kidney function to the point where the kidneys may permanently fail to work. When kidney disease causes permanent renal failure, it is called end-stage renal disease.