What is the difference between prerenal and renal acute kidney injury?

This paper discusses the somewhat artificial distinction between the traditional classification of acute kidney injury in prerenal AKI and established acute tubular necrosis. The primary focus in the setting of a rising SCr should not be assigning the diagnosis of"prerenal" or "renal" AKI but should be determining where the dysfunction lies on the spectrum between purely "functional"and completely structural kidney damage. The new definitions and classification systems of AKI are summarised and the approach to the patient with acute rising serum creatinine and/or acute decline in urinary output is described. The role of the recently introduced novel biomarkers is discussed but it is believed that these biomarkers have not yet proven to be more discriminative in the differential diagnosis between"pure prerenal AKI"and established acute tubular necrosis, beyond a careful clinical evaluation of the patient and the use of the more "traditional" blood and urine parameters.