Chronic kidney disease (CKD)

IRIS staging, the framework vets use

The International Renal Interest Society (IRIS) stages CKD on a 1–4 scale based on fasting creatinine and SDMA, then substages by proteinuria (UPC ratio) and blood pressure. Staging drives treatment intensity and prognosis.

• Stage 1, kidney damage with normal or mildly elevated renal markers. Often picked up incidentally.
• Stage 2, mild azotemia. Symptomatic disease usually still subtle.
• Stage 3, moderate azotemia. Clinical signs (PU/PD, weight loss, decreased appetite) typically present.
• Stage 4, severe azotemia. Uremic crisis risk, intensive intervention.

Diet is the highest-leverage intervention

Phosphorus-restricted, controlled-protein veterinary therapeutic renal diets have multiple randomized controlled trials showing extended survival in cats and dogs with IRIS Stage 2+ CKD. The effect size is meaningful, months to over a year of additional median survival. This is one of the highest-impact dietary interventions in companion-animal medicine, and it depends on owner compliance: switching the bag matters.

Supporting care

• Subcutaneous fluids, at home, typically 100–150 mL per administration in cats; frequency dictated by stage.
• Phosphate binders, when dietary restriction alone does not control serum phosphorus.
• Antiproteinurics (telmisartan, benazepril) when UPC ratio elevated.
• Antiemetics (maropitant) and appetite stimulants (mirtazapine, capromorelin) for inappetence.
• Blood pressure monitoring and management of systemic hypertension.

Why it matters

CKD is often diagnosed late, after substantial nephron loss. Annual senior bloodwork including SDMA picks it up earlier, while diet and supportive care still have room to extend quality and length of life. Skipping the prescription renal diet because it is more expensive is the single most common owner-driven failure in CKD management.