What is the definition of acute kidney injury (AKI)?

Acute kidney injury (AKI) is defined as the sudden inability of the kidneys to perform their essential function of filtering and removing excess fluids, minerals, and waste products from the blood. It often occurs within hours or days and can result from various causes, including impaired blood flow to the kidneys, direct damage to the kidney tissue, or an obstruction in the urinary tract. The key characteristic of AKI is its rapid onset, which distinguishes it from chronic conditions, hence making the definition focused on sudden changes in kidney function accurate.

The gradual loss of kidney function is typically associated with chronic kidney disease rather than AKI, which is why that option does not describe AKI properly. The complete failure of kidney function suggests end-stage renal disease (ESRD), which is a more permanent state rather than an acute condition. A chronic condition requiring regular dialysis indicates a long-term management approach for kidney failure rather than a sudden impairment in kidney function, further reinforcing that this option does not align with the definition of AKI.