Acute renal failure

Acute kidney injury

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

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%

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

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

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

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

AGN

Part of ‘Glomerulonephritis’