Acute kidney injury (AKI) has now replaced the term acute renal failure and an  universal definition and staging system has been proposed to allow earlier detection  and management of AKI. The new terminology enables healthcare professionals to  consider the disease as a spectrum of injury. This spectrum extends from less severe  forms of injury to more advanced injury when acute kidney failure may require renal  replacement therapy (RRT). Clinically AKI is characterised by a rapid reduction in  kidney function resulting in a failure to maintain fluid, electrolyte and acid-base  homoeostasis. There have previously been many different definitions of AKI used in  the literature which has made it difficult to determine the epidemiology and outcomes  of AKI. Over recent years there has been increasing recognition that relatively small  rises in serum creatinine in a variety of clinical settings are associated with worse  outcomes。