Definition of Acute Kidney Injury

?Acute?kidney?injury?(AKI)?is?the?abrupt?loss?of?kidney?function,?resulting?in?the?retention?of?urea?and other nitrogenous waste products and in the dysregulation of extracellular volume and electrolytes. The term AKI has largely replaced acute renal failure (ARF), reflecting the recognition that smaller decrements in kidney function that do not result in overt organ failure are of substantial clinical relevance and are associated with increased morbidity and mortality. The term ARF is now reserved for severe AKI, usually implying the need for renal replacement therapy. The loss of kidney function that defines AKI is most easily detected by measurement of the serum creatinine, which is used to estimate the glomerular filtration rate (GFR). Three problems are associated with the use of serum creatinine to quantitatively define AKI: