REVIEW OF KDIGO AKI RECOMMENDATIONS
Definition and Classification of AKI
Commentary
Overview. The first group of recommendation statements
in the KDIGO AKI Guideline addresses the
definition of AKI (Box 1). Of these 13 recommendation
statements, 12 are not graded. The KDIGOWork
Group began by defining AKI by harmonizing the
prior RIFLE and AKIN criteria.7,19 In the RIFLE
criteria (Table 1), AKI was defined based on a 50%
increase in serum creatinine level occurring over 1-7
days or the presence of oliguria for more than 6 hours.
The AKIN criteria added an absolute increase in
serum creatinine level of 0.3 mg/dL and reduced the
timeframe for the increase in serum creatinine level to
48 hours (Table 1). The KDIGO Work Group harmonized
these 2 definitions, keeping the absolute increase
in serum creatinine level of 0.3 mg/dL within
48 hours from the AKIN definition, but returning to the 7-day timeframe for the 50% increase in serum
creatinine level. With regard to pediatric AKI, the
KDIGO definition did not adopt the smaller changes
in estimated creatinine clearance proposed in the
pRIFLE criteria. Rather, the KDIGO Work Group
suggested that the absolute change in creatinine level
of 0.3 mg/dL that is part of the KDIGO AKI
definition would capture most pediatric AKI. The
KDIGO definition considers a decrease in estimated
glomerular filtration rate (eGFR) to 35 mL/min/
1.73 m2 to be stage 3 AKI in pediatric patients, as
initially proposed in the pRIFLE criteria.20
Overall, while our KDOQI Work Group concurred
with the efforts on the part of KDIGO to meld the RIFLE
and AKIN criteria into a uniform definition of AKI, we
have significant reservations regarding the applicability
of this definition and staging system to clinical practice.
The RIFLE and AKIN definitions and staging systems
have substantially enhanced the ability to conduct epidemiologic
studies, and we support the use of the KDIGO
AKI guideline definition and staging strategy for future
epidemiologic research until novel biomarkers facilitate
the development of better criteria. We concur that the
rigorous application of a standard definition will permit
epidemiologic comparisons across populations and over
time. In addition, the definitions as described have value
in standardization of entry criteria and endpoints in
clinical trials of AKI. However, we question whether
these criteria are currently appropriate to guide clinical
management of adult patients.