Acute Kidney Injury Flashcards
Acute kidney injury (AKI)
Sudden reduction in renal function following an insult to the kidneys
Risk factors for AKI
- > 65 years
- hx. AKI or CKD
- heart/liver failure
- diabetes
- cognitive impairment
- nephrotoxic meds
- contrast dyes
Main causes of AKI
- Pre-renal
- Intra-renal
- Post-renal
Pre-renal causes of AKI
(4)
- volume depletion/hypovolaemia (e.g. haemorrhage, GI loss)
- reduced cardiac output (e.g. HF)
- systemic vasodilation (e.g. septic shock, anaphylaxis)
- drugs (e.g. NSAIDs, ACE-i)
Causes of intra-renal AKI
(4)
- acute tubular necrosis (e.g. ischaemia, rhabdo)
- acute interstitial nephritis (e.g. drug-induced)
- vascular (e.g. renal artery thrombosis)
- glomerular (e.g. glomerulonephritis)
Causes of post-renal AKI
- obstruction (e.g. stones, tumours, strictures, prostatic hypertrophy)
Investigating suspected AKI
- urine analysis (dipstick, protein:creatinine)
- bloods
- ultrasound
Indications for ultrasound scan in AKI
all new AKI with unknown aetiology
Urinalysis findings for:
1) UTI, 2) glomerular nephritis, 3) acute interstitial nephritis
- leukocytes, nitrites
- haematuria, leukocytes
- leukocytes
Pre-renal vs. acute tubular necrosis
Urine Na+ (and %Na+ excreted)
pre-renal:
- < 20mmol
- < 1%
ATN:
- > 20mmol
- > 1%
kidneys retain Na in pre-renal to resolve hypovolaemia
Brown-casts in urine
acute tubular necrosis
AKI responds to fluid challenge
pre-renal causes
Pre-renal vs. acute tubular necrosis
% Urea excreted
pre-renal: < 35%
ATN: > 35%
NICE Criteria for AKI
- Rise in creatinine > 26 in 48hrs
- Rise in creatinine > 50% in 7 days
- Urine output < 0.5ml/kg/hr for > 6hrs
Staging AKI
3 stages
- Creatinine rise 1.5-1.9x baseline or < 0.5ml/kg/hr for 6hrs
- Creatinine rise 2-2.9x baseline or < 0.5ml/kg/hr for 12hrs
- Creatine rise > 3 baseline or < 0.5ml/kg/hr for 24hrs
