Classification of acute kidney injury: are we there yet?

Excerpt

Acute kidney injury (AKI) is associated with both significant morbidity and significant mortality. This has clearly been demonstrated in critically ill patients requiring renal replacement therapy following AKI, in whom there is excessive mortality even when corrected for age, gender, and severity of disease [1]. However, even relatively modest impairment of renal function must be considered an independent risk factor for mortality [2, 3]. The incidence of AKI appears to be increasing [4] although exact numbers are difficult to obtain given the lack of a uniform definition of either AKI or its manifestation as acute renal failure (ARF), with more than 30 definitions already published [5]. A step in the right direction was the development of the RIFLE criteria by the Acute Dialysis Quality Initiative (ADQI) [6]. In addition to an increase in serum creatinine, the RIFLE criteria include reduced urine output as a sensitive marker of renal dysfunction. On the basis of these two parameters renal impairment was classi fied into “risk”, “injury”, and “failure”, with two additional classes, “loss” and “end-stage renal disease”, defined by the requirement of renal replacement therapy for more than 4 weeks and more than 3 months, respectively [6]. Since its initial publication a number of studies have investigated the validity of the RIFLE criteria in classifying AKI/ARF in terms of both severity and outcome [7, 8, 9, 10, 11, 12]. The two largest studies reported are retrospective analyses of databases [11], one of them using only serum creatinines without urine outputs for the calculation of the RIFLE criteria [12]. …