Pre-Renal vs Intrinsic AKI
A rising creatinine tells you what changed — not why.
Start With Baseline and Trajectory
A creatinine rise confirms a change in kidney function; it does not distinguish reduced perfusion from structural injury or obstruction.
Start with baseline and trajectory before reaching for a diagnosis.
Build the Story Around the Kidneys
Look for poor intake, GI losses, hypotension, bleeding, infection, diuretics, ACEi/ARB, NSAIDs, contrast, urinary symptoms and obstruction risk.
Urinalysis and sediment can redirect the differential.
Pre-Renal Can Become Intrinsic
A hemodynamic AKI may evolve into tubular injury when hypoperfusion is severe or prolonged.
Persistent creatinine rise after the trigger is corrected should change your thinking.
Don't Let One Ratio Make the Diagnosis
BUN/Cr and fractional-excretion indices can support the pattern, but CKD, diuretics and mixed mechanisms limit their reliability.
Use these indices to support a coherent clinical story — not to replace it.
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