- 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.
- 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.
Manage fluid and electrolytes, discontinue causes if any, loop diuretics to manage hypovolemia in intrinsic kidney injury. Dopamine and fenoldopam are not recommended.