What is the acute kidney injury network (AKIN) classification system?

Updated: Dec 24, 2020
  • Author: Biruh T Workeneh, MD, PhD, FASN; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Answer

The Acute Kidney Injury Network (AKIN) has developed specific criteria for the diagnosis of AKI. The AKIN defines AKI as abrupt (within 48 hours) reduction of kidney function, manifested by any 1 of the following [3] :

  • An absolute increase in serum creatinine of 0.3 mg/dL or greater (≥26.4 µmol/L)
  • A percentage increase in serum creatinine of 50% or greater (1.5-fold from baseline)
  • A reduction in urine output, defined as less than 0.5 mL/kg/h for more than 6 hours

AKIN has proposed a staging system for AKI that is modified from RIFLE. In this system, either serum creatinine or urine output criteria can be used to determine stage. See Table 2, below.

Table 2. Acute Kidney Injury Network Classification/Staging System for AKI [3] (Open Table in a new window)

Stage

Serum Creatinine Criteria

Urine Output Criteria

1

Increase of ≥0.3 mg/dL (≥26.4 µmol/L) or 1.5- to 2-fold increase from baseline

< 0.5 mL/kg/h for >6 h

2

>2-fold to 3-fold increase from baseline

< 0.5 mL/kg/h for >12 h

3*

>3-fold increase from baseline, or increase of ≥ 4.0 mg/dL (≥35.4 µmol/L) with an acute increase of at least 0.5 mg/dL (44 µmol/L)

< 0.3 mL/kg/h for 24 h or anuria for 12 h

*Patients who receive renal replacement therapy (RRT) are considered to have met the criteria for stage 3 irrespective of the stage they are in at the time of RRT.


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