Fast Facts:
- Normal BUN: SCR = 10-15:1 = ATN (intrinsic acute kidney injury) Cellular Debris usually seen.
- Elevated BUN (20:1) or Urinary sodium < 20 or low Fractional Excretion of Sodium = pre-renal
- RIFLE Stratification of injury:
- Considered kidney injury when SCr increases 2 times baseline
- Failure when SCr increases 3 times baseline
- Risk of injury when SCr increases 1.5 times baseline
- Contrast-induced nephropathy: NS is the best fluid to clear, usually seen 24-48 hours after contrast.
Overview:
- Common complications of AKI include electrolyte imbalances and fluid overload.
- Pre-renal disease: kidney is initially undamaged, hypoperfusion of kidney, no sign of volume depletion, concentrated urine but no sediment.
- Functional Kidney Injury: undamaged kidney, usually related to medications (NSAIDs, cyclosporin, ACEIs, ARBs) or in patients with low effective blood flow (CHF, liver disease and older adults). Concentrated urine.
- Intrinsic AKI: damaged kidney, usually due to acute tubular necrosis. Neurotensive, euvolemic or hypervolemic, urine is generally not concentrated
- Post-renal AKI: kidney undamaged, usually caused by bladder outlet obstruction. Distended bladder, enlarged prostate.
Treatment:
Manage fluid and electrolytes, discontinue causes if any, loop diuretics to manage hypovolemia in intrinsic kidney injury. Dopamine and fenoldopam are not recommended.