Chronic Kidney Disease

Chronic kidney disease (CKD) is the most prevalent serious illness in older cats. Studies suggest it affects around 30–40% of cats over 10 years old and over 80% of cats over 15. The kidneys contain millions of tiny filtering units called nephrons. Once destroyed, nephrons cannot regenerate — meaning CKD is irreversible and progressive.

The kidneys perform several vital functions: filtering metabolic waste from the blood, regulating blood pressure, producing a hormone that stimulates red blood cell production, and controlling fluid and electrolyte balance. As nephron numbers decline, these functions deteriorate gradually — which is why early CKD is often completely silent. By the time clinical signs appear, 65–75% of kidney function has typically already been lost.

The International Renal Interest Society (IRIS) staging system helps vets classify CKD severity and guide treatment. Stage 1 has no clinical signs; Stage 4 is severe with multiple organ involvement. Regular blood and urine testing allows vets to track progression and adjust management.

Management focuses on slowing progression and maintaining quality of life. Renal diets are lower in phosphorus and protein (reducing the kidney's workload), and higher in omega-3 fatty acids. Subcutaneous fluid therapy — which many owners learn to administer at home — dramatically improves hydration and wellbeing. Phosphate binders, anti-nausea medications, appetite stimulants, and blood pressure medications are commonly used as the disease progresses.