Pre-renal Azotemia is characterized by all of the following. Except -
The fractional excretion of filtered sodium (FENa) has been demonstrated to be a reliably discriminating test between prerenal azotemia and acute tubular necrosis. One paicular urinary index cannot be expected to reliably discriminate between prerenal azotemia and acute renal failure in all cases Urinary Osmolality The normal kidney can elaborate urine with a maximum concentration greater than 1,200 mOsm/kg in states of dehydration. A urinary osmolality (Uosm) greater than 500 mOsm/kg,, is highly suggestive of prerenal azotemia And it is reversible with fluid replacement Ref Harrison20th edition pg 299
Fractional excretion of Na< 1%
Urinary osmolality > 500 mosm/kg
Urinary sodium concentration > 40 meq/1
Reversible with replacement fluids
Kidney