Table 2.

International Renal Interest Society (IRIS) grading criteria for acute kidney injury (AKI) in dogs and cats (adapted with permission from Borgarelli et al. (2001)

AKI grades	Serum creatinine	Clinical description
I	<1 · 6 mg/dL (<140 µmol/l)	Non-azotaemic AKI:
		a. Documented AKI: (Historical, clinical, laboratory or imaging evidence of acute kidney injury, clinical oliguria/anuria, volume responsiveness†)…and/or
		b. Progressive non-azotaemic increase in serum creatinine; ≥0.3 mg/dL (≥ 26.4 µmol/l) within 48 hours
		c. Measured oliguria (<1 ml/kg/hr) or anuria over 6 hours
II	1 · 7–2 · 5 mg/dL (141–220 µmol/L)	Mild AKI:
		a. Documented AKI and static or progressive azotaemia
		b. Progressive azotaemic increase in serum creatinine; ≥0.3 mg/dL (≥ 26.4 µmol/l) within 48 hours), or volume responsiveness†
		c. Measured oliguria (<1 ml/kg/h) or anuria over 6 hours
III	2 · 6–5 · 0 mg/dL (221–439 µmol/L)	Moderate to severe AKI:
		a. Documented AKI and increasing severities of azotaemia and functional renal failure
IV	5 · 1–10 · 0 mg/dL (440–880 µmol/L)
V	>10 · 0 mg/dL (>880 µmol/L)

Each grade of AKI is further sub-graded on the basis of oliguria, non-oliguric (NO) or oligoanuria (O), as well as any requirement for renal replacement therapy (RRT).

^†Volume responsive is an increase in urine production to >1 ml/kg/h over 6 hours; and/or decrease in serum creatinine to baseline over 48 hours)