Long-term outcomes of acute kidney injury.

Acute kidney injury (AKI) is common in the intensive care unit and is associated with significant morbidity and mortality. Based on the RIFLE criteria, AKI occurs in up to 67% of patients in the intensive care unit (ICU), with approximately 4% of critically ill patients requiring renal replacement therapy (RRT). It is well known that this subset of AKI patients who require RRT have an in-hospital mortality rate exceeding 50%. However, long-term outcomes of survivors of AKI requiring RRT remain poorly described. Long-term mortality is greater in those patients who survived AKI when compared with critically ill patients without AKI. Long-term morbidity, renal and extrarenal, is a frequent and underappreciated complication of AKI. Among survivors of AKI at long-term follow-up (1-10 years), approximately 12.5% are dialysis dependent (wide range of 1%-64%, depending on the patient population) and 19% to 31% have chronic kidney disease. According to the United States Renal Data System, "acute tubular necrosis without recovery" as a cause of end-stage kidney disease increased from 1.2% in 1994 to 1998 to 1.7% in 1999 to 2003. The incidence will likely continue to rise with the aging population, increase in comorbidities, and expansion of intensive care unit capabilities. AKI is an underrecognized cause of chronic kidney disease (CKD) and patients who survive should be followed closely for new CKD and/or progression of underlying CKD.