- Apply at 12 hours of PICU admission. Select the patient's highest applicable Risk tier: any PICU admission (1) → solid-organ / hematopoietic stem-cell transplant history (3) → invasive mechanical ventilation and ≥ 1 vasoactive infusion (5).
- Select the patient's highest applicable Injury tier from the worse of fluid overload (% FO) or % decrease in estimated creatinine clearance (ΔeCCl) vs. baseline.
- Optionally enter the measured FO% and ΔeCCl% — the calculator will suggest the matching Injury tier to confirm above.
- RAI = Risk × Injury (range 1–40). RAI ≥ 8 = renal angina present (high risk of severe Day-3 AKI); RAI < 8 = renal angina absent (high negative predictive value).
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When to Use
Apply the Renal Angina Index to critically ill children at 12 hours of PICU admission to identify those at high risk of severe AKI on Day 3 (KDIGO Stage 2 or greater). It is a triage and stewardship tool — not a diagnosis. A positive RAI defines the population that benefits from early renal consultation, urinary biomarker testing, nephrotoxin de-prescribing, and tightened fluid stewardship. A negative RAI carries a high negative predictive value and supports continued routine PICU monitoring.
Appropriate population
Children admitted to a pediatric ICU, evaluated at the 12-hour mark. The RAI is validated for predicting severe Day-3 KDIGO Stage 2+ AKI in this setting and has been deployed in single-center derivation cohorts and the multinational AWARE study (Basu 2014; Basu 2018).
When NOT to rely on it
The RAI is not intended for adults, for neonatal intensive care without local adaptation, or for patients already at KDIGO Stage 2+ AKI at the 12-hour mark (the score is for prediction, not diagnosis). A score below 8 does not mean "no kidney risk forever" — clinical trajectory, new sepsis, nephrotoxin exposure, and rising creatinine still require reassessment. Treat the RAI as a screening tool that focuses biomarker and consult resources, not as a replacement for clinical judgment.
Pearls & Pitfalls
Risk × Injury — take the highest applicable tier
Both Risk and Injury are single-select tiers: you assign the patient to the highest tier they meet, not the sum. A transplant recipient on mechanical ventilation with vasoactives is Risk 5 (not 3 + 5), and a child with FO 12% (Injury 4) and ΔeCCl 28% (Injury 2) is Injury 4 — the worse of the two. The optional FO% and ΔeCCl% fields below help select the right tier.
Pair the RAI with biomarkers, not just clinical gestalt
The RAI was designed to enrich the population that benefits from emerging AKI biomarkers — urinary NGAL, KIM-1, and the FDA-cleared [TIMP-2] × [IGFBP7] panel. When the RAI is positive, sending a biomarker has a substantially higher pre-test probability of identifying severe Day-3 AKI than routine PICU monitoring alone. When the RAI is negative, biomarker testing is generally low-yield.
Pitfalls
(1) Garbage in — fluid overload and baseline creatinine must be recorded accurately; a missing or estimated baseline weight invalidates the FO% calculation. (2) Single timepoint: the RAI is anchored to the 12-hour mark and was not validated for serial reapplication every shift. (3) "Renal angina absent" is not "no AKI possible" — it identifies a population in whom severe Day-3 AKI is unlikely given current data; reapply clinical judgment as the trajectory evolves. (4) The RAI does not stage AKI — use KDIGO / pRIFLE criteria for that.
Why Use It
Pediatric AKI is common in critical illness, often missed early, and strongly associated with mortality, prolonged ventilation, and long-term CKD. By the time AKI is "diagnosable" on Day 3 by creatinine, the window for nephroprotective intervention — nephrotoxin de-prescribing, fluid stewardship, biomarker-guided escalation — has narrowed. The Renal Angina Index, modeled on cardiac angina as a clinical syndrome that triggers further testing, gives the PICU team a fast, structured way at the 12-hour mark to convert vague risk into a defensible enrichment criterion for downstream testing and consultation. It has been derived and validated in pediatric cohorts (Basu 2014) and deployed prospectively in the multinational AWARE study (Basu 2018), where it consistently outperformed clinician gestalt for identifying children destined for severe Day-3 AKI.
Renal Angina Index (Pediatric AKI Prediction at 12 h)
Select the patient's highest applicable Risk tier and highest applicable Injury tier at the 12-hour mark of PICU admission. Optionally enter % fluid overload (FO) and % decrease in estimated creatinine clearance (ΔeCCl) — the tool will suggest the matching Injury tier. RAI = Risk × Injury (range 1–40); ≥ 8 = renal angina present.
⚕ Basu RK et al. Kidney Int. 2014;85(3):659–667; Basu RK et al. (AWARE) Lancet Child Adolesc Health. 2018;2(2):112–120. The Renal Angina Index identifies critically ill children at the 12-hour PICU mark who are at high risk of severe Day-3 KDIGO Stage 2+ AKI. A positive RAI is not a diagnosis of AKI — it is an enrichment criterion for biomarker testing, nephrotoxin de-prescribing, and early nephrology consultation. Interpret alongside trajectory and the full clinical picture.
Next Steps
Use the 12-hour RAI to direct enrichment, stewardship, and consultation.
- RAI ≥ 8 — renal angina present: intensify monitoring (hourly urine output, daily creatinine and weight); send a urinary biomarker panel where available (NGAL, KIM-1, [TIMP-2] × [IGFBP7]); audit and de-prescribe nephrotoxins (aminoglycosides, vancomycin, NSAIDs, contrast, calcineurin inhibitors); tighten fluid stewardship; obtain early pediatric nephrology consultation.
- RAI < 8 — renal angina absent: continue standard PICU monitoring; routine biomarker testing is generally low-yield. Reapply clinical judgment and re-evaluate if the trajectory deteriorates (new sepsis, nephrotoxin exposure, rising creatinine, worsening fluid balance).
- Stage any established AKI with KDIGO / pRIFLE criteria using the pediatric AKI staging tool; estimate function with bedside Schwartz eGFR.
- Document the 12-hour RAI in the chart with its components, so subsequent trajectory (Day-3 KDIGO stage, biomarker results, fluid balance) can be reviewed against the prediction.
Evidence & References
Scoring
| Domain | Tier (single-select, highest applicable) |
|---|---|
| Risk | 1 = PICU admission · 3 = transplant (HSCT or solid-organ) · 5 = mechanical ventilation and ≥ 1 vasoactive |
| Injury (worse of FO% or ΔeCCl%) | 1 = FO < 5% / ΔeCCl 0–<25% · 2 = FO 5–<10% / ΔeCCl 25–<50% · 4 = FO 10–<15% / ΔeCCl 50–<75% · 8 = FO ≥ 15% / ΔeCCl ≥ 75% |
| RAI | Risk × Injury (range 1–40) |
| Threshold | ≥ 8 = renal angina present (predicts Day-3 KDIGO Stage 2+ AKI) |
Interpretation
| RAI at 12 h | Interpretation |
|---|---|
| < 8 | Renal angina absent — high negative predictive value for severe Day-3 KDIGO Stage 2+ AKI |
| ≥ 8 | Renal angina present — enriches the population for biomarker testing, nephrotoxin stewardship, and early nephrology consultation |
Basu and colleagues derived and validated the RAI in critically ill children, demonstrating high negative predictive value for severe Day-3 AKI; the multinational AWARE prospective study confirmed its performance across diverse pediatric ICUs.
References
- Basu RK, Zappitelli M, Brunner L, et al. Derivation and validation of the renal angina index to improve the prediction of acute kidney injury in critically ill children. Kidney Int. 2014;85(3):659–667.
- Basu RK, Kaddourah A, Goldstein SL; AWARE Study Investigators. Assessment of a renal angina index for prediction of severe acute kidney injury in critically ill children: a multicentre, multinational, prospective observational study. Lancet Child Adolesc Health. 2018;2(2):112–120.
- Goldstein SL, Mottes T, et al. AKI biomarker panel + RAI multicenter study (integrating NGAL, KIM-1, and [TIMP-2] × [IGFBP7] with the renal angina index in pediatric critical care).
