Parameter Prerenal ATN
Concentration of urine:
Urine specific gravity > 1.020 < 1.010
Urine Osmolarity (mosm/lit)) > 500 < 350
GFR and overall tubular reabsorption:
Creatinine clearance > 20 < 20
Urine/Plasma urea > 8 < 3
Urine/Plasma creatinine > 40 < 20
Tubular handling of solutes
UNa (mEq/L) < 20 > 40
FeNa (%) < 1 > 1
B- Urinary sediment:
Centrifugation of fresh urine sample and examination of the urinary
sediment may be helpful in diagnosing different causes of ARF. See the
chapter on value of urine examination in medical diagnosis. In pre-renal
failure and in ischaemic ATN urinary sediment is usually free.
C- Renal Imaging:
- Plain film of the abdomen:
This will show kidney parity, size, shape, calcification and stones. - Renal Ultrasonography and echo-doppler of renal vessels: