IRIS CKD Staging Calculator (Cats & Dogs)

Stage chronic kidney disease from creatinine and SDMA, then substage by proteinuria and blood pressure.

IRIS stages chronic kidney disease by fasting blood creatinine. Cats: stage 1 under 1.6 mg/dL, stage 2 1.6–2.8, stage 3 2.9–5.0, stage 4 over 5.0. Dogs: stage 1 under 1.4, stage 2 1.4–2.8, stage 3 2.9–5.0, stage 4 over 5.0. SDMA can move a patient up a stage, and each stage is substaged by proteinuria (UPC) and systolic blood pressure.

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How to use it

  1. Choose cat or dog.
  2. Enter a fasted blood creatinine from a stable patient; add SDMA if you have it.
  3. Add the urine protein:creatinine ratio and systolic blood pressure to substage.

What you enter

What you get

Formula

Stage by creatinine (mg/dL): cat <1.6 | 1.6–2.8 | 2.9–5.0 | >5.0; dog <1.4 | 1.4–2.8 | 2.9–5.0 | >5.0. SDMA (µg/dL): cat <18 | 18–25 | 26–38 | >38; dog <18 | 18–35 | 36–54 | >54. µmol/L = mg/dL × 88.4.

Staging applies only to stable chronic kidney disease, on at least two fasted samples; acute kidney injury is graded differently.

Worked example: 14-year-old cat

Input: Creatinine 2.2 mg/dL, SDMA 28 µg/dL, UPC 0.3, systolic 165 mmHg

Result: Stage 2 by creatinine; SDMA suggests stage 3; borderline proteinuric; hypertensive

Manage as stage 3 if SDMA stays high on a repeat test, and treat the hypertension.

Questions

What creatinine is stage 3 kidney disease in cats?

IRIS stage 3 in cats is a blood creatinine of 2.9–5.0 mg/dL (251–440 µmol/L), or an SDMA of 26–38 µg/dL. Stage 4 is above 5.0 mg/dL or SDMA above 38 µg/dL.

How does SDMA change the IRIS stage?

SDMA rises earlier than creatinine. If SDMA is persistently above 25 µg/dL in a cat or 35 µg/dL in a dog staged as stage 2 by creatinine, especially one with low muscle mass, IRIS suggests treating it as the next stage up.

What are the IRIS substages?

Proteinuria by urine protein:creatinine ratio (non-proteinuric under 0.2; borderline 0.2–0.4 in cats and 0.2–0.5 in dogs; proteinuric above that) and systolic blood pressure (under 140 normotensive, 140–159 prehypertensive, 160–179 hypertensive, 180 or more severely hypertensive).

Limitations

References

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All free tools · By Dr. Zubair Khalid, DVM, MS, PhD.