Acute Kidney Injury Flashcards
What is AKI?
An abrupt decline in kidney function/GFR
- Disrupts ECF volume, electrolyte and acid-base homeostasis
- Accumulation of nitrogenous waste products
How is AKI actually defined?
By any of the following:
- Increase in serum creatinine by >26.5 umol/L within 48 hours
- Increase in serum creatinine by >1.5 times baseline within 7 days
- Urine volume <0.5 ml/kg/h for 6 hours (oliguria)
What are the three types of AKI causes?
Pre-renal, intrinsic and post-renal (obstruction)
Name some causes of AKI
Hypovolaemia, cardiac failure, renal artery occlusion
Vasculitis, glomerular disease, acute tubular necrosis, acute interstitial nephritis, intratubular obstruction
Bladder outlet obstruction, renal calculi
Globally, what are the commonest causes of AKI?
Hypotension and dehydration
In pre-renal AKI, why is GFR reduced?
Decreased renal blood flow
can be compensated by autoregulation
What are some causes of prerenal AKI?
Reduced arterial blood volume: hypovolaemia, vasodilation (like in sepsis), cardiac failure
Impaired renal autoreglation: pre-glomerular vasoconstriction (NSAIDs), post-glomerular vasodilation (ACEi)
What can cause acute tubular necrosis?
Ischaemia, nephrotoxins, sepsis
Which sites are most prone to damage in acute tubular necrosis?
Proximal tubule and thick ascending limb
What are some endogenous nephrotoxins?
Myoglobin, urate, bilirubin
What are some exogenous nephrotoxins?
Drugs (NSAIDs, gentamicin), poisons, X ray contrast
How may a crush injury damage the kidneys?
Rhabdomyolysis - release of myoglobin which is nephrotoxic
How does myoglobinuria appear?
Very dark ‘coca-cola urine’
What are some post renal causes of AKI?
Stones, blood clots, tumours, enlarged prostate, aortic aneurysm
What are some complications of AKI?
Metabolic acidosis, hyperkalaemia, hyponatraemia
