The utility of urinary biochemistry has recently been challenged , while there is emerging evidence that renal biomarkers may accurately quantify the risk of development of acute kidney injury (AKI) . Neutrophil gelatinase-associated lipocalin (NGAL) is a marker of renal tubular damage . Fractional excretion of sodium (FENa) is a marker of renal tubular function, and is a significantly cheaper investigation . Insults damaging the tubules and resulting in AKI should both stimulate NGAL production and prevent resorption of sodium. Given the different pathological mechanisms underlying septic and nonseptic AKI, it is plausible that the relationship between these variables could be different in these two groups of patients .