Which criterion is used to stage acute kidney injury?

• A. RIFLE Criteria
• B. AKIN Criteria
• C. KDIGO Criteria
• D. MELD Score

Answer: (A)

Staging acute kidney injury is about classifying its severity based on how much kidney function has declined over a short period, using objective changes in serum creatinine and urine output. The RIFLE system was the original framework that defined three levels of severity—Risk, Injury, and Failure—based on specific increases in creatinine or decreases in GFR, along with urine output criteria, with two additional outcomes called Loss and End-stage. This structured approach gives clinicians a clear sense of how severely the kidney is affected and helps guide treatment and prognosis. Although newer criteria like AKIN and KDIGO later refined and updated these definitions, RIFLE is the historical criterion specifically designed to stage AKI, which is why it is the correct choice here. The MELD score, by contrast, is used to assess liver disease severity and is not used to stage AKI.