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Acute renal failure
- 2. ARF
Sudden- <48 hours- decrease in renal
function
Results in inability to excrete nitrogenous
waste & maintain fluid-electrolyte balance
Present in-
~30% of ICU admissions
~5% of hospital admissions
Develops in ~25% of in-patients
Measured by rising serum creatinine
- 3. Classification
Pre-renal- decreased renal perfusion- ~50%
Renal- ~40-45%
Acute tubular necrosis- ATN- ~80%
ischemic or toxic insult
Acute interstitial nephritis- AIN- ~15%
mostly drug-induced inflammatory
response
Acute glomerulonephritis- AGN- ~5%
immunological glomerular injury
Post-renal- obstruction of B/L urinary tract,
increasing intraluminal pressure- ~5-10%
- 4. ARF- pre-renal
Commonest cause of ARF
Due to renal hypoperfusion, due to-
Decreased intravascular volume- hemorrhage, diarrhea,
dehydration, pancreatitis, burns, diuresis
Change in vascular resistance- shock, NSAIDs, ACEI,
vasopressors, cyclosporin, renal artery stenosis
Low cardiac output- cardiogenic shock, CHF, PE,
pericardial tamponade
Dx- clinical scenario & BUN/Cr ratio >20
Rx- of underlying cause, fluid repletion
- 5. ARF- post-renal
Due to obstruction of urinary flow, due
to-
Urethral valve/stricture
Bladder outlet obstruction- BPH, prostate/bladder ca.
B/L ureteric obstruction- cervical cancer, stones, clots
Dx- clinical scenario & ultrasound/CT
Rx- relieve obstruction
Beware of post-obstructive diuresis
- 6. ATN- proximal tubule
Causes-
Ischemia- surgery, trauma, rhabdomyolysis, prolonged hypoperfusion
Nephrotoxins- aminoglycosides, radiocontrast, Amphotericin,
Vancomycin, Cyclosporin
Dx- clinical scenario & urinanalysis-muddy granular cast,
hyperkalemia is common
Rx- recovery heralded by diuresis
Monitoring & supportive treatment
Diuretics- loop ± thiazides
Dialysis- hyperkalemia, fluid overload, acidosis, encephalopathy
Px- better for non-oliguric patient &
worse for surgical illness
- 7. AIN
Interstitial edema & inflammation
Causes-
Drugs- penicillins, cephalosporins, sulfonamides, NSAIDs
Infections- streptococcal, leptospirosis, CMV, RMSF
s/s- fever, rash, arthralgia
Dx- eosinophilia & eosinophiluria, WBC casts
Rx- remove inciting drug & supportive Rx,
steroids & dialysis in severe prolonged cases