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Open Access Highly Accessed Research

A comparison of RIFLE with and without urine output criteria for acute kidney injury in critically ill patients

Kama A Wlodzimirow1*, Ameen Abu-Hanna1, Mathilde Slabbekoorn2, Robert AFM Chamuleau3, Marcus J Schultz4 and Catherine SC Bouman4

Author Affiliations

1 Department of Medical Informatics, Academic Medical Center, University of Amsterdam, Meibergdreef 9, Amsterdam, 1105 AZ, The Netherlands

2 Department of Intensive Care, Medisch Centrum Haaglanden, Lijnbaan 32, The Hague, 2512 VA, The Netherlands

3 Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, University of Amsterdam, Meibergdreef 69-71, Amsterdam, 1105 BK, The Netherlands

4 Department of Intensive Care, Academic Medical Center, University of Amsterdam, Meibergdreef 9, Amsterdam, 1105 AZ, The Netherlands

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Critical Care 2012, 16:R200  doi:10.1186/cc11808

Published: 18 October 2012

Abstract

Introduction

The Risk, Injury, Failure, Loss, and End-Stage Renal Disease (RIFLE) is a consensus-based classification system for diagnosing acute kidney insufficiency (AKI), based on serum creatinine (SCr) and urine output criteria (RIFLESCr+UO). The urine output criteria, however, are frequently discarded and many studies in the literature applied only the SCr criteria (RIFLESCr). We diagnosed AKI using both RIFLE methods and compared the effects on time to AKI diagnosis, AKI incidence and AKI severity.

Methods

This was a prospective observational cohort study during four months in adult critically ill patients admitted to the ICU for at least 48 hours. During the first week patients were scored daily for AKI according to RIFLESCr+UO and RIFLESCr. We assessed urine output hourly and fluid balance daily. The baseline SCr was estimated if a recent pre-ICU admission SCr was unknown. Based on the two RIFLE methods for each patient we determined time to AKI diagnosis (AKI-0) and maximum RIFLE grade.

Results

We studied 260 patients. A pre-ICU admission SCr was available in 101 (39%) patients. The two RIFLE methods resulted in statistically significantly different outcomes for incidence of AKI, diagnosis of AKI for individual patients, distribution of AKI-0 and distribution of the maximum RIFLE grade. Discarding the RIFLE urine criteria for AKI diagnosis significantly underestimated the presence and grade of AKI on admission and during the first ICU week (P < 0,001) and significantly delayed the diagnosis of AKI (P < 0.001). Based on RIFLESCr 45 patients had no AKI on admission but subsequently developed AKI. In 24 of these patients (53%) AKI would have been diagnosed at least one day earlier if the RIFLE urine criteria had been applied. Mortality rate in the AKI population was 38% based on RIFLESCr and 24% based on RIFLESCr+UO (P = 0.02).

Conclusions

The use of RIFLE without the urine criteria significantly underscores the incidence and grade of AKI, significantly delays the diagnosis of AKI and is associated with higher mortality.