AKI describes a rapid decline in renal function (days to weeks) leading to azotemia with/without oliguria.
It is used interchangeably with acute renal failure.
The clinical definition is an increase in Scr and a decrease in urine output for a period of fewer than 3 months.
Classification
- AKI is classified according to what is the source of the problem, i.e. is it:
- Prerenal (reduced perfusion)
- Intrarenal (intrinsic kidney disease)
- Postrenal (obstruction).
- Pre-renal and intrarenal are divided into oliguric renal failure (worse) and non-oliguric renal failure.
Prerenal failure
- Most common cause of AKI. There's no structural damage to the kidney, but rather just loss of perfusion.
- CHF and liver cirrhosis can sometimes hide hypovolemia.
- Causes include:
- Hypovolemia (dehydration)
- Decrease in effective circulatory volume (cirrhosis, PAH, HF, shock)
- Drugs with vascular disease (ACEi/ARBs with renal artery stenoses, NSAIDs and renal hypoperfusion).
- Hyperosmolar urine with low sodium.
- Increased sodium resorption (low urinary sodium).
- Increased BUN/sCr due to an