Differential diagnosis of acute kidney failure

1. Big picture

Acute kidney failure, better called acute kidney injury (AKI), is a sudden fall in kidney function causing retention of nitrogenous waste, fluid, acid, potassium, and drugs.

For the final exam, do not start with rare nephrology diseases. Start with the practical emergency algorithm:

Confirm AKI
→ assess life-threatening complications
→ decide prerenal vs intrinsic renal vs postrenal
→ stop nephrotoxins
→ restore perfusion or relieve obstruction
→ treat the cause
→ dialyze if AEIOU indications are present

The most common cause is prerenal hypoperfusion, especially dehydration, shock, sepsis, heart failure, or reduced effective circulating volume. The attached question file also states that prerenal causes are responsible for more than half of AKI cases, renal causes for about 40%, and postrenal causes for about 5%.

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