From the Guidelines
The Acute Kidney Injury (AKI) criteria are defined as any of the following: increase in serum creatinine by ≥0.3 mg/dL within 48 hours, increase in serum creatinine to ≥1.5 times baseline within 7 days, or urine volume <0.5 mL/kg/h for 6 hours, as per the KDIGO guidelines 1. The most widely used criteria are KDIGO (Kidney Disease: Improving Global Outcomes), which stages AKI in severity from 1-3 based on the magnitude of creatinine rise or duration of oliguria.
- Stage 1 involves creatinine 1.5-1.9 times baseline or ≥0.3 mg/dL increase, or urine output <0.5 mL/kg/h for 6-12 hours.
- Stage 2 involves creatinine 2.0-2.9 times baseline or urine output <0.5 mL/kg/h for ≥12 hours.
- Stage 3 involves creatinine ≥3.0 times baseline, increase to ≥4.0 mg/dL, initiation of renal replacement therapy, urine output <0.3 mL/kg/h for ≥24 hours, or anuria for ≥12 hours, as outlined in the KDIGO guidelines 1 and further explained in 1. These criteria are important because early detection of AKI allows for prompt intervention, potentially preventing progression to more severe kidney damage and improving patient outcomes, with follow-up evaluations recommended 3 months after AKI to assess for resolution, new onset, or worsening of pre-existing chronic kidney disease (CKD) 1.
From the Research
Definition of Aki Criteria
- The Acute Kidney Injury Network defines the first stage of AKI by either an absolute or a percentage increase in serum creatinine (SCr) 2.
- Kidney Disease: Improving Global Outcomes (KDIGO) defines AKI as an increase in the serum creatinine (SCr) level of 0.3 mg/dL or more within 48 hours, an SCr level increase of 1.5 times or more of the baseline level within 7 days, or a decrease in urine output to less than 0.5 mL/kg/hour for 6 hours 3, 4.
- AKI can also be defined as an increase in serum creatinine or a decrease in urine output over hours to days 5.
Key Components of Aki Criteria
- Increase in serum creatinine level
- Decrease in urine output
- Time frame for these changes (e.g. 48 hours, 7 days)
- Baseline kidney function 2, 3, 4.
Clinical Application of Aki Criteria
- Determining the cause of AKI is critical when possible 3.
- Management of AKI includes control of the underlying cause, achievement and maintenance of euvolemia, nutritional optimization, blood glucose control, and pharmacotherapy 3.
- Referral to a nephrology subspecialist is recommended for patients with stage 2 or 3 AKI, or if the etiology of the AKI is unclear 3.