eGFR / CKD-EPI (2021)

NephrologyCKD-EPI Collaboration

Glomerular filtration rate (GFR) is the best overall index of kidney function and is used to stage chronic kidney disease (CKD), guide drug dosing, and time renal replacement therapy. The CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) creatinine equation was developed in 2009 and updated in 2021 to remove the race coefficient, making it race-free and reducing racial disparities in CKD care. It uses serum creatinine, age, and sex to estimate GFR and is more accurate than the Cockcroft-Gault and MDRD equations, particularly at higher GFR values. The National Kidney Foundation now recommends the 2021 race-free CKD-EPI as the primary equation for CKD staging.

8 criteria6 pearls3 refsValidated

KDIGO AKI Staging

NephrologyKDIGO AKI Guideline Work Group

Open

The KDIGO (Kidney Disease: Improving Global Outcomes) AKI staging system was published in 2012 to provide a unified, internationally standardised definition and classification of acute kidney injury. Prior to KDIGO, inconsistent AKI definitions (RIFLE, AKIN) led to challenges in comparing study populations. KDIGO defined AKI as any of: increase in serum creatinine by ≥0.3 mg/dL within 48 hours, increase to ≥1.5× baseline within 7 days, or urine output <0.5 mL/kg/hour for ≥6 hours. Even small creatinine rises (Stage 1) independently predict mortality and hospital length of stay.

4 criteria6 pearls3 refsValidated

Validated In

Retrospective validation across multiple ICU and hospital cohorts worldwide

KDIGO AKI Guideline Work Group

AKI Definition

SCr ↑ ≥0.3 mg/dL in 48h OR ↑ ≥1.5× baseline in 7 days OR UO <0.5 mL/kg/hr ≥6h

Stage 1 (Mild)

SCr ↑ ≥0.3 mg/dL OR ↑ 1.5-1.9× baseline OR UO <0.5 mL/kg/hr for 6-12h

Stage 2 (Moderate)

SCr ↑ 2.0-2.9× baseline OR UO <0.5 mL/kg/hr for ≥12h

Stage 3 (Severe)

SCr ↑ ≥3× baseline OR ≥4.0 mg/dL OR UO <0.3 mL/kg/hr ≥24h OR anuria ≥12h

AKI Stage 1 doubles 30-day mortality; Stage 3 is associated with 50% in-hospital mortality in critically ill patients.

Use the LOWEST creatinine over the preceding 3-6 months as "baseline" when available — this prevents over-staging.

RRT (haemodialysis or CRRT) indications in Stage 3 AKI: severe hyperkalemia (K+ >6.5), refractory metabolic acidosis (pH <7.1), volume overload unresponsive to diuretics, uraemic complications (pericarditis, encephalopathy).

Urine output criteria are often underutilised — a patient with normal creatinine but oliguria for 12+ hours meets Stage 2 criteria and warrants nephrology input.

Novel biomarkers (NGAL, KIM-1, TIMP-2 × IGFBP7) can detect AKI earlier than creatinine, particularly useful in cardiac surgery patients.

AKI → CKD transition: 25-30% of AKI survivors develop new or worsened CKD — follow serum creatinine at 3 months post-discharge.

[1]

KDIGO Clinical Practice Guideline for Acute Kidney Injury. Kidney Int Suppl. 2012;2(1):1-138.

[2]

Hoste EA, et al. KDIGO Controversies Conference on Acute Kidney Injury: report of an international panel. Kidney Int. 2020;98(6):1477-1490.

[3]

Chawla LS, et al. Acute kidney disease and renal recovery: consensus report of the Acute Disease Quality Initiative (ADQI) 16 Workgroup. Nat Rev Nephrol. 2017;13(4):241-257.

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Clinical References

Nephrology2 results

eGFR / CKD-EPI (2021)

KDIGO AKI Staging