Acute kidney injury, including acute tubular necrosis
Description
- Abrupt fall in GFR over hours to days, with retention of nitrogenous waste and dysregulation of volume and electrolytes
KDIGO staging - creatinine OR urine output, whichever is worse
| Stage | Creatinine | Urine output |
|---|---|---|
| 1 | 1.5-1.9x baseline, OR rise >=26.5 micromol/L in 48h | <0.5 mL/kg/h for 6-12 h |
| 2 | 2.0-2.9x baseline | <0.5 mL/kg/h for >12 h |
| 3 | >=3x baseline, OR rise to >=353.6 micromol/L, OR initiation of RRT | <0.3 mL/kg/h for >=24 h, or anuria >=12 h |
- Creatinine is a late and insensitive marker - GFR may have halved before it moves
- Oliguria = <0.5 mL/kg/h; anuria (<50 mL/day) means obstruction, vascular catastrophe, or severe cortical necrosis until proven otherwise
Three buckets - the framework for every case
- Pre-renal (~40-70%) - hypoperfusion, tubules intact, reversible on restoring perfusion
- Intrinsic (~10-50%) - ATN >> AIN > glomerular > vascular
- Post-renal (~5-10%) - obstruction; must be excluded in everyone, it is the one that is fully reversible
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