Acute kidney injury is characterized by abrupt deterioration in kidney function, manifested by an increase in serum creatinine level with or without reduced urine output. Creatinine comes the metabolism of creatine in skeletal muscle and dietary meat intake. Creatinine is normally freely filtered across the glomeruli and not reabsorbed in the tubules. Acute renal injury can be classified as prerenal (decreased perfusion of the normal kidney), intrarenal pathologic change within the kidney itself or postrenal (also called postobstructive).