Acute renal failure (ARF) has traditionally been defined as the abrupt loss of kidney function that results in the retention of urea and other nitrogenous waste products and in the dysregulation of extracellular volume and electrolytes. The loss of kidney function is most easily detected by measurement of the serum creatinine which is used to estimate the glomerular filtration rate (GFR).
The classification/staging system for acute kidney injury is as follow:
Stage 1
- Increase in serum creatinine of more than or equal to 0.3 mg/dL (≥26.4 mircomol/L) or increase to more than or equal to 150 to 200 percent (1.5- to 2-fold) from baseline.
- Urine output less than 0.5 mL/kg per hour for more than 6 hours.
Stage 2
- Increase in serum creatinine to more than 200 to 300 percent (>2- to 3-fold) from baseline.
- Urine output less than 0.5 mL/kg per hour for more than 12 hours.
Stage 3
- Increase in serum creatinine to more than 300 percent (>3-fold) from baseline (or serum creatinine of more than or equal to 4.0 mg/dL [≥354 micromol/L] with an acute increase of at least 0.5 mg/dL [44 micromol/L]).
- Urine output less than 0.3 mL/kg per hour for 24 hours or anuria for 12 hours.