Acute renal failure is defined as a significant detioration in renal function occuring over hours to days.
It is usually oliguric (<500mls/24 hrs)
However, it is non-oliguric in 10% of cases, including:
- gentamycin/amphotericin toxicity
- radio-contrast nephropathy
- interstitial nephritis
When approaching renal failure everyone repeats the mantra 'is it pre-renal, renal or post-renal'. A recap of a few of the causes follows:
Pre-renal causes:
- sepsis
- hypovolaemia
- cardiac failure
- liver failure
- NSAIDS/ACE-i (interfere with renal blood flow)
Renal causes (generally acute tubular necrosis):
- nephrotoxic drugs
- gentamycin
- amphotericin
- tetracyclines
- contrast agents
- myeloma
- myoglobin (rhabdomyolysis)
- vasculitis
- glomerulonephritis
Post renal:
- any urinary tract obstruction
Important points to enable one to distinguish ATN from pre-renal uraemia are shown in the table below:
Essentially in pre-renal failure the kidneys are still working so are trying to concentrate the urine, whereas in ATN they aren't.
Going through the management of acute renal failure is a bit beyond the scope of this battle (and if you're taking MRCP you are probably already very familiar with it) so I'll finish by just briefly recapping indications for dialysis:
- refractory pulmonary oedema
- persistent hyperkalaemia (>7mmol/l)
- severe metabolic acidosis (pH<7.2 or BE <10)
- uraemic encephalopathy
- uraemic pericarditis
Thats all the battles for today. Tomorrow we're back for a mixed bag before embarking on another renal day....
