Table 1:
AKI Classification Systems
| RIFLE (7 Days) | AKIN (48 Hours) | KDIGO |
|---|---|---|
| Risk | Stage 1 | Stage 1 |
| Increased sCr × 1.5 or GFR decrease >25% OR urine output <0.5 ml kg–1 h–1 for 6 h |
Increased sCr × 1.5–2 or sCr increase ≥0.3 mg dl–1 OR urine output <0.5 ml kg–1 h–1 for >6 h |
Increased sCr × 1.5–1.9 within seven days OR sCr increase ≥0.3 mg dl–1 within 48 h OR urine output <0.5 ml kg–1 h–1 for 6-12 h |
| Injury | Stage 2 | Stage 2 |
| Increased sCr × 2 or GFR decrease >50% OR urine output <0.5 ml kg–1 h–1 for 12 h |
Increased sCr × 2–3 OR urine output <0.5 ml kg–1 h–1 for >12h |
Increased sCr × 2–2.9 OR urine output <0.5 ml kg–1 h–1 for ≥12h |
| Failure | Stage 3 | Stage 3 |
| Increased sCr × 3 or GFR decrease by 75% or sCr ≥ 4 mg dl–1 with an acute rise in sCr (≥0.5 mg dl–1) OR urine output <0.3 ml kg–1 h–1 for 24 h or anuria for 12 h |
Increased sCr × 3 or more or sCr ≥ 4 mg dl–1 with an acute rise in sCr (≥0.5 mg dl–1) OR urine output <0.3 ml kg–1 h–1 for >24 h or anuria for 12 h |
Increased sCr × 3 or more or sCr ≥ 4 mg dl–1 or initiation of RRT or GFR decrease to <35 ml min–1 (1.73 m) –2 in patients <18 yr old OR urine output <0.3 ml kg–1 h–1 for ≥24 h or anuria for ≥12 h |
| Loss | ||
| Persistent acute renal failure=complete loss of kidney function >4 weeks | ||
| End-stage Kidney Disease | ||
| ESRD >3 months | ||
Comparison of the three most notable and historic classification systems used to diagnose AKI. The initial system was the RIFLE (Risk, Injury, Failure, Loss of kidney function, End-stage renal failure), which was developed by an international consensus in 2004. It defined 5 stages of renal injury: risk-end stage disease. A short time later the Acute Kidney Injury Network (AKIN) developed their own diagnostic criteria that uses a smaller creatinine change to define AKI. This was based on studies showing that even small changes in serum creatinine resulted in adverse outcomes.2–6 In 2012, the KDIGO (Kidney Disease: Improving Global Outcomes) classification system was produced and has been the main system in use since.9 The KDIGO system was created by combining the two prior systems and utilizing studies showing which patients were missed by the two prior classification system.