Postoperative acute kidney injury

Acute kidney injury (AKI) represents 18-47% of all causes of hospital-acquired AKI and it is associated with a high incidence of morbidity and mortality especially in patients requiring dialysis. Only recently, with the application of new AKI classifications and guidelines (RIFLE, AKIN and KDIGO), a more accurate evaluation of the real incidence of kidney dysfunction in patients undergoing surgery has been detailed. In patients undergoing non-cardiac, non-vascular and non-thoracic surgery several independent preoperative and intraoperative predictors of AKI have been identified. Nonetheless, no measure for AKI prevention reached a high level of recommendation, although hemodynamic monitoring and goal-directed fluid management may limit perioperative AKI. Cardiac surgery-related AKI and cardiopulmonary bypass-related AKI have been extensively evaluated and several preventive and treatment strategies have been developed. Open and endovascular surgery-related AKI have been compared and hydration is currently the only preventive strategy with a substantial level of efficacy. In addition, AKI in thoracic surgery, overlooked in the past, has been evaluated, showing that it frequently complicates postoperative course of patients undergoing elective lung cancer resection. Multi-hit mechanisms (ischemia, inflammation, toxins) co-act on patients' predisposition (susceptibility). A multi-step approach is probably necessary to limit the incidence and the severity of postsurgery AKI patients, such as careful risk stratification, adoption of preventive measures and goal directed intraoperative algorithms. The present review will summarize the current literature about the epidemiology of postoperative AKI focusing on patient-related and technical-related risk factors, outcome and prevention strategies in different groups of surgeries.