Table 9.1-4. Selected differential features of prerenal azotemia and intrinsic AKI

 

Prerenal AKI

Intrinsic AKI

Daily urine output (mL)

<400

Variable

Urine osmolality (mOsm/kg H2O)

>500

<350

Urine specific gravity (g/mL)

>1.023

≤1.012

Ratio of urea (mmol/L) to serum creatinine (micromol/L)

>1:10

 <1:10

Ratio of urinary to serum creatinine concentration

>40

<20

Urinary [Na+] concentration (mmol/L)a

<20

>40

Fractional excretion of sodiumb

<1%

>2%

Urine sediment

No abnormal findings or hyaline casts only

Epithelial cells, pigmented muddy-brown granular casts or tubular epithelial cell casts

a Urinary sodium concentration (this should be measured before administering furosemide).

b Fractional excretion of sodium: FENa = [(urinary Na concentration in mmol/L × serum creatinine concentration in mg/dL) / (serum Na concentration in mmol/L × urinary creatinine concentration in mg/dL)] × 100%.

AKI, acute kidney injury.