Question 1

How do I determine the baseline creatinine for staging?

Accepted Answer

Use the lowest known creatinine in the preceding 3–7 days. If unavailable, a pre-admission outpatient value is preferred. When no previous value exists, the MDRD equation can back-estimate a baseline assuming eGFR 75 mL/min/1.73m², but this is a poor substitute for an actual measured baseline.

Question 2

Does the staging system account for the cause of AKI?

Accepted Answer

No. Staging reflects severity, not aetiology. The cause (prerenal, intrinsic, postrenal) is determined separately through history, exam, urinalysis, and imaging. Both dimensions are needed for management.

Question 3

Should I use creatinine or urine output criteria?

Accepted Answer

Both. The stage is determined by whichever criterion gives the higher stage. Urine output criteria often detect AKI hours before the creatinine rises, but it requires accurate urine output measurement (indwelling catheter).

Question 4

How do I stage AKI in a patient on dialysis?

Accepted Answer

A patient who initiates renal replacement therapy (RRT) for AKI is automatically classified as KDIGO Stage 3, regardless of the creatinine/urine output at the time of RRT initiation.