Acute Renal Failure

• Definition - acute deterioration in glomerular filtration rate
• Diagnostic features - acute elevation in serum creatinine +/- oliguria
• Commonest (and most readily treatable) cause is impaired renal blood flow (pre-renal failure) - see Shock
• Rapid treatment is required to prevent progression to acute tubular necrosis
• ED management focuses on addressing reversible causes - optimize circulatory status/re-establishing urine output, relieving distal obstruction (IDC), treating UTIs, eliminating potential nephrotoxins
• Refer to nephrologist for other treatments - dialysis, treating acute glomerulonephritides, managing systemic conditions - diabetes, hypertension, connective tissue disease
• Refer to ICU - if invasive haemodynamic monitoring or dialysis required to manage patient
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Causes

Pre-renal

• (see Shock) - commonest cause

Renal

• Drugs/Toxins - NSAIDS/aspirin, ACE-I, diuretics, aminoglycosides, snake venom, radio-contrast
• Other - rhabdomyolysis, haemolysis
• Acute Glomerulonephritis - streptococcal infection, other immunologically mediated

Post renal

• Bladder outlet obstruction - BPH, tumours
• Bilateral ureteric obstruction - calculi, tumours, retroperitoneal haematomas

Complications

• Hyperkalaemia (see Emergency Treatment of Hyperkalaemia)
• Metabolic acidosis
• Fluid overload/Acute pulmonary oedemia
• Acute tubular necrosis - increased risk of infection/ARDS

Diagnostic features

• Urine output < 10ml/hr (may not be present)
• Acute rise in creatinine

Investigation

• EUC
• Ca²⁺/PO₄^3-   - altered in chronic renal failure
• FBC - anaemia in sub-acute/chronic renal failure
• Serum CK, urine myoglobin - if rhabdomyolysis suspected
• Urinalysis, urine MCS - looking for UTI, rhabdomyolysis
• Urine sediment - casts/cells suggest  intrinsic insult or acute glomerulonephritis
• Renal ultrasound - if upper tract obstruction suspected

Management

• Fluid resuscitate (+/- invasive haemodynamic monitoring) - see Shock
• Insert IDC and measure urine output hourly - Bolus 500ml normal saline until urine output > 40ml/hr
• Treat cause - Antibiotics for UTI, eliminate nephrotoxins e.g. drugs, blood transfusions
• Treat complications - hyperkalaemia, acute pulmonary oedema

Indications for dialysis

(consult with nephrologist/intensivist)

• Severe hyperkalaemia/metabolic acidosis
• Acute pulmonary oedema
• Oliguria despite fluid resuscitation

Disposition

• ICU - if invasive haemoynamic monitoring or dialysis required to manage patient
• Nephrology - in acute glomerulonephritides or dialysis anticipated
• Urology consult - if upper tract obstruction demonstrated