The classical compartmentalisation of pre-renal, intra-renal and post-renal factors holds true in the intensive care unit with the following considerations:
A missed, but reversible, cause of renal failure has dire consequences.
Renal perfusion (blood flow and GFR) in critically ill patients may become directly related to systemic blood pressure as local auto regulation fails. Hypotension, even a marginal decrease, will not be well tolerated.
The renal interstitium is relatively hypoxic even under optimal conditions. When subjected to a multilevel endothelial insult as a result of sepsis or SIRS there is a predisposition to a vasomotor nephropathy and progression to overt ATN.
The pharmacokinetics of many drugs in intensive care are severely deranged, exposing the patient to a much greater risk of nephrotoxic effects. Drugs and toxins (including radio-contrast) should not be administered without consideration of their toxicity.
Occult or overt increases in intra-abdominal pressure should always be considered in patients with abdominal distension with or without previous surgery. When considered it should be measured and if necessary addressed.