Acute kidney injury/impairment (AKI), formerly known as acute renal failure (ARF) is a deterioration of renal function over a period of hours to days that results in failure of the kidney to perform its necessary processes. These include the elimination of nitrogenous waste products, homeostasis of fluids and electrolytes, acid-base balance, gluconeogenesis, and hormone production. An elevation in nitrogenous wastes is referred to as azotemia. Uremia is the clinical manifestation of azotemia and consists of nausea and vomiting, altered sensorium, pruritus, asterixis, decreased appetite, and pericarditis. Acute intrinsic kidney injury is considered to be the most diverse in terms of underlying cause of injury, as it results from functional or direct structural damage to any part of the kidney, including the small blood vessels, glomerulus, renal tubule, and interstitium. Postrenal obstruction is characterized by an acute onset of anuria.