Table 1.

Urinary index equations and reference values.

Urinary indices	Formula	Traditional reference value
FeNa	FeNa = [(Nau/NaS)/(cru/crP)] × 100	<1% transient AKI >1% persistent AKI
FeU	FeU = [(Uu/US)/(cru/crP)] × 100	<35% transient AKI >35% persistent AKI

Na—sodium, cr—creatinine, u—urinary, S—serum, P—plasma, U—urea, and AKI—acute kidney injury. Modified from [20, 37].