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Etiology of Acute Renal Failure

Prerenal Causes

Any condition that significantly reduces renal perfusion pressure and causes a decreased glomerular filtration rate and azotemia may cause prerenal kidney failure. Clinical conditions that may result in prerenal kidney failure include but are not limited to: extracellular fluid losses secondary to burns, prolonged vasoconstriction (hypertension), and reduced cardiac output as seen in patients with shock syndrome or congestive heart failure. If prerenal failure is identified early and treated correctly, the kidney dysfunction may be reversible. If the underlying cause continues to affect renal perfusion, it may lead to ischemic damage to the nephron and acute tubular necrosis (ATN).

Renal Causes

Actual damage to the nephrons and renal parenchyma characterize intrarenal failure. Clinical conditions that result in intrarenal damage can be categorized under kidney disease or acute tubular necrosis. ATN is a common type of acute renal failure in the critically ill patient. The use of nephrotoxic drugs (streptomycin, penicillin, and amphotericin) in older patients or in individuals with underlying renal insufficiency place patients at a higher risk of developing ATN. The risk for ATN is also higher in patients with prolonged prerenal factors. ATN is a potentially reversible type of renal failure but it may take weeks or months before adequate renal function returns.

Post-renal Causes

Post-renal failure is caused by clinical conditions that cause obstruction to urine flow. Any problem that stops the excretion of urine may cause this type of ARF. Common conditions associated with post-renal failure are tumors, benign prostatic hypertrophy, kidney stones and bladder neck obstruction. If post-renal failure is untreated it may result in actual nephron damage and intrarenal failure.