Alterations in renal function are common after surgical emergencies, trauma, and major operations. In these settings, successful recovery of renal function is dependent on prompt diagnosis and protective management strategies. Acute kidney injury (AKI) is characterized by an acute decrease in glomerular filtration rate (GFR). The true incidence of AKI and acute renal failure (ARF) has been difficult to define, given the broad and various definitions used to quantify and study altered renal function. Relatively recent introduction of consensus definitions, such as RIFLE (risk, failure, loss, and end-stage renal failure) criteria and AKIN (Acute Kidney Injury Network) staging, have provided standard definitions to facilitate more uniform outcome reporting. With use of these definitions, recent studies suggest that AKI occurs in up to two thirds of patients in the intensive care unit (ICU). Moreover, increasing severity of AKI is associated with increasing mortality. AKI is also associated with increased morbidity, such as increased hospital length of stay and cost of care, and has been linked to other in-hospital complications, such as increased difficulty in weaning from mechanical ventilation. Preoperative risk factors for development of AKI include older age, emergent surgery, hepatic disease, obesity, high-risk surgery, vascular disease, and chronic obstructive pulmonary disease (COPD). Prompt recognition of AKI facilitates effective treatment. Although the incidence rate of AKI appears to be rising, overall outcomes from AKI are gradually improving.
The reported mortality rate of AKI is 30% to 60%. If RRT is necessary, reported mortality rates are over 50%. The reason for such high mortality is that AKI now usually occurs as part of a spectrum of multiple organ failure, most often associated with severe sepsis or septic shock. The mortality in this setting is often determined by the underlying septic syndrome, rather than by complications of individual organ failure. Of surviving patients of AKI, a significant number have development of chronic renal insufficiency, which necessitates chronic dialysis. The precise rate of development of chronic renal failure varies greatly in the literature, depending on the patient populations. A recent review of AKI estimates that overall, the risk of necessary chronic dialysis is approximately 12%.