Definition and Classification of Acute Kidney Injury in Pediatric Patients

pRIFLE Classification System

The pediatric-modified RIFLE (pRIFLE) criteria are the standard for defining AKI in children over 1 month of age, which stages AKI based on decreases in estimated GFR (eGFR), rises in serum creatinine, or decreases in urine output 1, 2
The pRIFLE system classifies pediatric AKI into three stages, including Risk (Stage 1), Injury (Stage 2), and Failure (Stage 3), based on specific criteria such as eGFR decrease, rise in creatinine, and urine output 1, 3

If no prior creatinine is available within the previous 3 months, baseline kidney function can be imputed by assuming a normal GFR of 100 ml/min/1.73 m² and using the patient's height 2, 4
The revised "Bedside Schwartz equation" is recommended for calculating eGFR in children, using the formula GFR (ml/min per 1.73 m²) = 0.413 × (height in cm) ÷ (creatinine in mg/dl) or GFR (ml/min per 1.73 m²) = 36.5 × (height in cm) ÷ (creatinine in mmol/l) 2, 5

Small changes in serum creatinine may represent relatively large changes in actual GFR in pediatric patients 6, 4
The pRIFLE definition has not been validated for neonates (under 1 month of age) and further research is needed before it can be recommended for this population 1, 2

The Kidney Disease: Improving Global Outcomes (KDIGO) guidelines refer to pRIFLE for defining AKI in children, and include criteria such as rise of ≥26 μmol/l (0.3 mg/dl) within 48 hours or 50-99% rise in creatinine from baseline within 7 days 2, 3, 4

Accurate height measurement is necessary to calculate eGFR using the Schwartz formula, which can be challenging in sick, ventilated patients 2
Enzymatic assays for creatinine measurement are preferred for pediatric populations due to the low creatinine values encountered in children 2, 5
Studies show correlation between increasingly severe AKI and adverse outcomes, highlighting the importance of early detection and proper management 2