Smart protocols
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Use this page as a reference. When you are ready to stage a patient, Vetool keeps the workflow in one place: species, creatinine unit, SDMA, UPC, systolic blood pressure, warnings, and the final IRIS classification.
Start with stable, diagnosed CKD
IRIS staging starts after chronic kidney disease has been diagnosed. An increased creatinine or SDMA value alone does not diagnose CKD.
Interpret results alongside history, physical examination, urinalysis, imaging, urine concentrating ability, proteinuria, and previous laboratory findings. IRIS recommends staging with creatinine, SDMA, or ideally both, assessed in a stable, adequately hydrated patient on at least two occasions when possible.
Do not assign a fixed CKD stage when:
- The patient is dehydrated or hypovolemic.
- Renal values are changing quickly.
- Acute kidney injury, obstruction, or another postrenal cause has not been addressed.
- Only one isolated result is available and the clinical picture is unclear.
Step 1: choose the right species and unit
Creatinine ranges differ between dogs and cats. Use the table that matches both the species and the unit reported by the laboratory.
| IRIS stage | Dogs, mg/dL | Dogs, umol/L | Cats, mg/dL | Cats, umol/L |
|---|---|---|---|---|
| Stage 1 | Below 1.4 | Below 125 | Below 1.6 | Below 140 |
| Stage 2 | 1.4 to 2.8 | 125 to 250 | 1.6 to 2.8 | 140 to 250 |
| Stage 3 | 2.9 to 5.0 | 251 to 440 | 2.9 to 5.0 | 251 to 440 |
| Stage 4 | Above 5.0 | Above 440 | Above 5.0 | Above 440 |
A patient can have Stage 1 CKD even when creatinine is inside the laboratory reference interval, but only when other evidence of kidney disease is present.
Step 2: add SDMA when available
Creatinine and SDMA are both surrogate markers for glomerular filtration. Using both can give more context than relying on one result alone.
| IRIS stage | Dogs, ug/dL | Cats, ug/dL |
|---|---|---|
| Stage 1 | Below 18 | Below 18 |
| Stage 2 | 18 to 35 | 18 to 25 |
| Stage 3 | 36 to 54 | 26 to 38 |
| Stage 4 | Above 54 | Above 38 |
IRIS SDMA guidance is based on published work using IDEXX SDMA methodology. Results from other methods may not be directly equivalent.
Step 3: slow down when creatinine and SDMA disagree
Creatinine and SDMA can place the same patient in different stages. That does not automatically mean one value is wrong.
Check hydration, recent fluid therapy, muscle mass, body condition, previous trends, concurrent illness, breed or body size, lab method, and sample quality. Marked muscle loss can make creatinine look lower than expected for the degree of renal dysfunction.
The IRIS pocket guide says to consider muscle mass and retest both markers in 2 to 4 weeks. If values stay discordant, consider assigning the higher stage.
Example: a stable cat has creatinine in Stage 2 and SDMA in Stage 3. Review hydration, muscle mass, previous values, and trend. If the discrepancy persists after reassessment, manage the patient as Stage 3.
Step 4: add proteinuria substage
The primary stage does not describe the whole case. UPC adds a separate proteinuria substage.
| Species | Non-proteinuric | Borderline proteinuric | Proteinuric |
|---|---|---|---|
| Dog | Below 0.2 | 0.2 to 0.5 | Above 0.5 |
| Cat | Below 0.2 | 0.2 to 0.4 | Above 0.4 |
Before classifying the patient, rule out pre-renal and postrenal causes of proteinuria when possible. IRIS recommends basing substaging on at least two urine samples collected over at least two weeks.
Step 5: add blood pressure substage
Systolic blood pressure is the second IRIS substage. Let the patient acclimatize, take multiple readings, and confirm the category across repeated visits when possible.
| Systolic blood pressure | IRIS substage | Risk of future target organ damage |
|---|---|---|
| Below 140 mmHg | Normotensive | Minimal |
| 140 to 159 mmHg | Prehypertensive | Low |
| 160 to 179 mmHg | Hypertensive | Moderate |
| 180 mmHg or higher | Severely hypertensive | High |
Some dog breeds, especially sighthounds, can have higher expected blood pressure. Use breed-specific reference ranges when available. Evidence of target organ damage also changes urgency.
Step 6: reassess stage and substages over time
IRIS staging is not a permanent label. Update the classification when creatinine, SDMA, UPC, blood pressure, treatment, or the patient's clinical condition changes. If antihypertensive or antiproteinuric treatment changes the current result, document the new substage and note that the patient is receiving treatment.
Where CKD staging usually drifts
The staging tables are short. Most mistakes happen in the context around them.
Stage becomes diagnosis
IRIS staging follows CKD diagnosis. It does not replace the work needed to confirm a chronic, persistent renal abnormality.
An unstable patient receives a fixed stage
Dehydration, acute kidney injury, obstruction, and rapid changes in renal function can alter creatinine and SDMA. Stabilize and reassess first.
One marker is interpreted alone
Creatinine and SDMA may not agree. When both are available, compare them and investigate the mismatch rather than ignoring one value.
Muscle mass is overlooked
Creatinine can underestimate renal dysfunction in patients with marked muscle loss.
Substaging is left unfinished
A primary stage without UPC and blood pressure leaves two clinically relevant parts of the case unclassified.
Treated values lose context
Current UPC or blood pressure may describe controlled disease rather than the original severity. Document treatment that affects classification.
What the final classification should include
A complete IRIS CKD classification should include the primary IRIS stage, creatinine basis, SDMA basis when available, proteinuria substage, blood pressure substage, relevant treatment status, and any context that changes interpretation.
Example: IRIS CKD Stage 2, borderline proteinuric, severely hypertensive. After treatment, the same patient may be reclassified using current UPC and blood pressure values, with treatment status documented.
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References
- International Renal Interest Society. IRIS Staging of CKD, modified in 2023.
- International Renal Interest Society. Diagnosing, Staging, Treating Chronic Kidney Disease in Dogs and Cats.
- International Renal Interest Society. Treatment Recommendations for CKD in Dogs, 2023.
- International Renal Interest Society. Treatment Recommendations for CKD in Cats, 2023.
Disclaimer
For veterinary professional education and workflow support only. This guide does not diagnose chronic kidney disease or replace clinical judgment, patient-specific assessment, current IRIS guidance, local regulations, or current veterinary references.