A seventy-six (76) year old man is admitted to the ICU following a laparotomy for faecal peritonitis. He has developed Multiple System Organ Failure over two days, requiring ventilatory and inotropic support. He is oliguric, increasingly acidotic, uraemic and has a rising serum creatinine.
(a) List the likely mechanisms for this patient’s renal failure.
Likely mechanisms include pre-renal, renal and post-renal causes.
Pre-renal renal failure includes hypovolaemia (inadequate resuscitation), hypotension (inadequate perfusion pressure compared to his normal BP, ? hypertensive), and impaired cardiac output (myocardial depression, myocardial ischaemia/infarction, arrhythmias).
Renal mechanisms include toxins (circulating, nephrotoxic drugs [eg. aminoglycosides]) and microcirculatory failure (sepsis and inflammatory response) with medullary ischaemia, tubular obstruction and vasoconstriction (acute tubular necrosis).
Post-renal mechanisms include increased intra-abdominal pressure, ureteric obstruction and catheter problems (unrecognised, resulting in obstruction).
Again, this is a question where the candidate is expected to demonstrate a systematic approach to the evaluation of renal failure.
In that, the question closely resembles Question 16 from the first paper of 2004, except in 2004 the patient was suffering from pneumonia and the candidate had to evalue their oliguria.
Given the differences between the two questions, the answer from 2004 is appropriately modified and reproduced below.
2) Discriminate between renal success and renal failure.
Likely mechanisms of renal failure in a patient with multi-organ system failure and septic shock