How is acute kidney injury defined?

• A. Abrupt increase in serum creatinine or a decrease in urine output
• B. Gradual decline in eGFR over months
• C. Stable creatinine with a normal urine output
• D. Chronic proteinuria with preserved creatinine

Answer: (A)

Acute kidney injury is a sudden loss of kidney function, defined by an abrupt rise in serum creatinine or a significant drop in urine output. This captures the acute nature of the problem, which can develop over hours to days and requires urgent assessment and management. The other options describe chronic or stable states: a gradual decline in eGFR over months points to chronic kidney disease, stable creatinine with normal urine output suggests no kidney injury, and chronic proteinuria with preserved creatinine indicates a chronic nephropathy rather than an acute event.