Chronic Kidney Disease in Cats: Early Signs & Dietary Management
Dr. James O'Brien, DVM
Omelo Vet · Licensed Veterinarian
CKD affects approximately 30% of cats over age 10. The kidneys' compensatory ability means early detection through regular testing is critical for management.
Chronic kidney disease (CKD) is one of the most common conditions in older cats, affecting approximately 30% of cats over the age of 10 and up to 80% of cats over 15. Unlike acute kidney injury, which develops suddenly following a toxic exposure or ischaemic event, CKD is a slow, progressive loss of kidney function over months to years.
**Understanding how the kidneys compensate**
Cats have remarkable renal reserve capacity. The kidneys can function with up to 75% of nephrons (functional kidney units) lost before clinical signs appear. This means by the time a cat shows obvious symptoms of kidney disease, significant damage has already occurred.
This is the primary reason early detection through regular blood and urine screening in senior cats is so important. Detecting kidney disease at IRIS Stage 1 or early Stage 2 (based on creatinine, SDMA, and urine specific gravity) allows intervention that meaningfully slows progression.
**SDMA: The early marker**
Symmetric dimethylarginine (SDMA) is now included in most routine senior wellness panels because it becomes elevated when approximately 25% of kidney function is lost - compared to creatinine, which only rises when 75% is lost. Regular SDMA testing allows identification of early kidney disease years before it would otherwise be detected.
**Clinical signs of CKD**
Early (IRIS Stage 1–2):
- Often none, or very subtle changes
- Urine becoming less concentrated (lower specific gravity)
- Subtle increase in thirst and urination
- Very mild weight loss
Moderate to advanced (IRIS Stage 3–4):
- Marked increase in thirst and urination (polyuria/polydipsia)
- Weight loss, muscle wasting
- Decreased appetite, nausea, vomiting
- Mouth ulcers, halitosis with a urine-like odour
- Poor coat quality
- Lethargy and weakness
- Hypertension (can cause sudden blindness if untreated)
**Dietary management**
The renal diet is one of the most evidence-based interventions in veterinary medicine - studies in cats with CKD show that renal diets approximately double median survival time compared to maintenance diets.
Key features of renal diets:
- Reduced phosphorus: Phosphorus accumulation in CKD worsens progression - renal diets restrict phosphorus to reduce this
- Controlled (not necessarily reduced) high-quality protein: Protein restriction in CKD is nuanced - inadequate protein leads to muscle wasting; excessive protein produces more uraemic toxins. Modern renal diets aim for moderate, high-quality protein
- Increased omega-3 fatty acids: Anti-inflammatory; may slow progression
- Increased potassium: CKD cats often waste potassium
- Alkalinising formulation: Metabolic acidosis is common in CKD
Transition to a renal diet should be gradual and voluntary - forcing a sick cat to eat a new food they find unpalatable is counterproductive. If appetite is severely compromised, appetite stimulants may be needed.
**Additional management**
- Phosphate binders: Given with meals to bind dietary phosphate in the gut if phosphorus is elevated
- Subcutaneous fluids: Many owners learn to administer fluids at home to support hydration
- Anti-nausea medication: Maropitant or ondansetron to manage nausea
- Antihypertensive therapy: Amlodipine if blood pressure is elevated
- Erythropoiesis-stimulating agents: For anaemia secondary to reduced erythropoietin production
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