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Kidney Disease in Pets
Chronic kidney disease is one of the most common conditions in older cats, and is increasingly recognised in dogs. Early detection and management can significantly extend a good quality of life.
What is Chronic Kidney Disease?
The kidneys perform essential functions: filtering waste products from the blood, regulating fluid balance, controlling blood pressure, and producing hormones that stimulate red blood cell production. In chronic kidney disease (CKD), the functional tissue of the kidney is progressively destroyed and replaced with scar tissue.
Because the kidneys have significant reserve capacity, signs of CKD do not appear until around 75% of kidney function is lost. This means the condition can be present and progressing for years before it is detected — particularly in cats, who compensate remarkably well.
CKD affects approximately 30–40% of cats over the age of 10. It is also common in older dogs, particularly certain breeds. It cannot be reversed but can be managed, and many animals live well for years after diagnosis.
IRIS Staging
CKD is staged using the International Renal Interest Society (IRIS) classification, based on creatinine (and increasingly SDMA — symmetric dimethylarginine, which detects decline earlier):
Non-azotaemic — creatinine normal but SDMA may be elevated, or urine abnormalities present. No symptoms. Management focuses on monitoring and identifying underlying causes.
Mild azotaemia — creatinine mildly elevated. Many animals show no symptoms yet. Diet change recommended. Close monitoring every 3–6 months.
Moderate azotaemia — symptoms often become apparent. Increased thirst and urination, reduced appetite, early weight loss. More intensive management required.
Severe azotaemia — uraemic symptoms. Vomiting, severe lethargy, very poor appetite, uraemic breath. Quality of life significantly affected. End-stage.
Signs & Symptoms
Increased thirst & urination
One of the earliest signs. The damaged kidneys lose their ability to concentrate urine, so more water is needed and more dilute urine is produced.
Weight loss
Often gradual and missed until significant. Muscle wasting, particularly over the spine and hindquarters in cats, is characteristic.
Reduced appetite
Declining interest in food, particularly in later stages when uraemic toxins suppress appetite.
Vomiting
Caused by the accumulation of waste products (uraemia). Can be intermittent in Stage 2–3 and more persistent in Stage 4.
Lethargy
Reduced energy, sleeping more, less interest in interaction or play.
Poor coat
Dull, unkempt coat — particularly in cats who stop grooming thoroughly.
Bad breath
A distinctive ammonia-like or "uraemic" odour — a sign of advanced kidney failure.
Oral ulcers
In advanced stages, uraemic toxins can cause ulceration of the mouth, making eating painful.
Management
- ▸Renal diet: Reduced phosphorus and controlled protein. Phosphorus restriction slows progression significantly. These diets should be introduced gradually and only if the animal will eat them — forcing an inappetent cat onto a renal diet is counterproductive.
- ▸Hydration: Encouraging fluid intake is crucial. Wet food (tinned or pouches) has much higher water content than dry food. Water fountains encourage drinking in cats. Some patients benefit from subcutaneous fluid administration at home.
- ▸Phosphate binders: Added to food to reduce phosphate absorption when diet alone is insufficient. Aluminium hydroxide, calcium carbonate, or newer options like lanthanum carbonate.
- ▸Blood pressure management: Hypertension is common and accelerates kidney damage. Amlodipine is first-line treatment in cats; telmisartan is increasingly used.
- ▸Anti-nausea medication: Maropitant or ondansetron for nausea and vomiting in stages 3–4.
- ▸Appetite stimulants: Mirtazapine (available as a transdermal gel for cats) can help maintain appetite and weight in later stages.
- ▸Erythropoietin: For anaemia caused by reduced kidney hormone production. Darbepoetin is the preferred option in veterinary patients.
Quality of Life & End Stage
Stage 4 CKD carries a poor prognosis. When the kidneys can no longer remove toxins adequately, uraemia causes profound illness — nausea, weakness, oral pain, and a general state of feeling very unwell. It is not a comfortable way to decline.
Signs that end-stage kidney disease is causing significant suffering include: persistent vomiting despite medication, complete loss of appetite, profound weakness, oral ulcers making eating impossible, apparent confusion or "uraemic encephalopathy," and a pet who has simply stopped engaging with life.
When management can no longer maintain a reasonable quality of life, a planned, peaceful farewell at home is often the kindest choice. It prevents unnecessary suffering and allows your pet to leave in the place they know best.
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