The development of perioperative acute renal failure is associated with high incidence of morbidity and mortality. An anesthesiologist's main objective for perioperative renal protection is identification of patients who are at risk, maintainace of euvolemia, preservation of adequate renal perfustion, avoidance of nephrotoxins and pharmacological prophylaxis. The aim of this essay is to study the physiology and pharmacology of the kidney ; the characterization of tests of renal function ; the cause of postoperative renal dysfunction ; what is presently available for its prevention and treatment and the effect of postoperative renal impairment on pateint outcome