In a recent study that used a definition of pre-renal azotemia, which was very similar to ours, cystatin C, NGAL, IL-18 and KIM-1 were elevated in ICU patients with pre-renal AKI compared to those without AKI, but were lower than values for patients whose AKI did not resolve within 48 hrs [27]. Here, IL18 is linked to acute kidney injury.