Kidney Disease in Cats: Stages, Symptoms & Management

Kidneys filter waste from blood, regulate hydration, and balance electrolytes. In CKD, nephrons — the functional units of the kidney — are damaged and lost over time. Waste products accumulate, and the cat cannot concentrate urine properly.

CKD is progressive but manageable. Cats may remain in early stages for years with appropriate care, or decline more quickly depending on the underlying cause and coexisting conditions.

• Age — most common in cats over seven years
• Prior kidney injury — infections, toxins (lilies, antifreeze), blockages
• Congenital abnormalities — polycystic kidney disease in some breeds
• Hyperthyroidism — can mask or worsen kidney changes
• High blood pressure — damages kidneys and results from kidney disease

Many cases are idiopathic — no single cause identified.

Early CKD may show only subtle changes:

• Increased thirst and urination — often the first sign owners notice
• Mild weight loss
• Reduced appetite
• Poor coat quality
• Bad breath (uremic odour) as disease progresses

Advanced CKD causes:

• Significant weight loss and muscle wasting
• Vomiting and nausea
• Lethargy and weakness
• Ulcers in the mouth
• Anaemia — pale gums, cold extremities
• High blood pressure — vision changes or neurological signs

Vets stage CKD using IRIS guidelines based on creatinine, SDMA, and urine concentration, guiding treatment intensity.

Senior wellness bloodwork and urinalysis detect CKD before clinical signs appear. SDMA is a sensitive early marker that may rise before creatinine. Urine specific gravity assesses concentrating ability. Blood pressure measurement and urine protein checks complete the picture.

Renal prescription diets

Low phosphorus, controlled protein, and added omega-3 fatty acids reduce kidney workload. Transition gradually — cats must actually eat the diet for it to help.

Hydration support

• Encourage water intake with fountains and wet food
• Subcutaneous fluids at home for moderate to advanced CKD
• IV fluids during dehydration crises

Medications

• Phosphate binders if diet alone does not control phosphorus
• Anti-nausea drugs — maropitant, mirtazapine for appetite
• Potassium supplementation if deficient
• Blood pressure medication — amlodipine commonly used
• Erythropoietin-stimulating agents for anaemia in later stages

Monitoring

Recheck bloodwork every three to six months — more often if unstable — adjusts treatment as the disease progresses.