Hello,

Urinary electrolytes are somewhat helpful in assessing AKI. If you decided a patient was volume contracted, then the appropriate response of the kidney is to conserve sodium - even down to 0 mmol/L (or fractional excretion <1%). However, if sodium is not low when the kidney should be conserving it, this is consistent with ATN as the tubules are unable to behave as they should. In terms of post-renal failure, you might find that hyperkalemia is present out of keeping with the degree of renal failure (so hyperkalemia at lower serum creatinine) - but this is not a hard and fast rule. Electrolytes do not help much in diagnosing GN.

There is a nice Medscape article on this linked below.

Dr. Jordan Weinstein