Acute Renal Failure (ARF) is the sudden loss of kidney functionality. The causes of ARF are classified into three categories such as prerenal, renal, and postrenal. Prerenal ARF is caused by problems that affect the flow of blood, before it enters the kidneys. Postrenal ARF is caused by problems in passing of urine out of the kidneys. Renal ARF is caused by problems with the kidney itself, resulting in the improper filtration of blood or disrupted production of urine.