By Sarah Bennett
Chronic Kidney Disease in Cats: What Every Owner Should Know
Chronic kidney disease (CKD) is one of the most frequently diagnosed conditions in older cats, affecting an estimated 30 to 40 per cent of cats over the age of twelve. Despite how common it is, many owners do not spot the early signs until the condition has already progressed. Understanding what to look for, how vets stage the disease, and what modern management looks like can make a real difference to your cat's comfort and longevity.
Recognising the Clinical Signs
The kidneys perform several essential functions: filtering waste products from the blood, regulating fluid balance, producing hormones, and controlling blood pressure. When kidney function declines, these processes become impaired and a range of clinical signs can emerge. In the early stages, symptoms are often subtle, which is why routine health checks matter so much for senior cats.
The most commonly reported signs of feline CKD include:
- Increased thirst and urination (polyuria and polydipsia, often abbreviated PU/PD)
- Gradual and unexplained weight loss, particularly muscle wasting along the spine
- Reduced appetite or complete loss of interest in food
- Occasional or frequent vomiting, especially in the morning
- A dull, unkempt coat due to reduced grooming and poor nutrient absorption
- Bad breath with a distinctive ammonia or uraemic smell (halitosis)
- Lethargy and a general reduction in activity levels
- Mouth ulcers in more advanced cases
If your cat is drinking noticeably more than usual and using the litter tray more frequently, this combination alone warrants a veterinary appointment. Early intervention consistently leads to better outcomes.
How Vets Diagnose CKD
Diagnosis involves a combination of blood tests, urinalysis, and in some cases imaging. Your vet will assess several key markers to understand both the severity of kidney impairment and its underlying cause.
Creatinine and SDMA
Creatinine has long been used as a standard indicator of kidney function. However, creatinine levels only become elevated after approximately 75 per cent of kidney function has already been lost. Symmetric dimethylarginine (SDMA) is a newer biomarker that can detect kidney disease much earlier — sometimes when as little as 25 per cent of function has been lost. WSAVA guidelines now recommend SDMA as part of routine senior screening, and many forward-thinking practices include it in annual blood panels for cats over seven years old.
Urine Specific Gravity
A urine specific gravity (USG) test measures how well the kidneys concentrate urine. Healthy cats produce concentrated urine; in CKD, the kidneys lose this ability and urine becomes more dilute. A persistently low USG alongside elevated creatinine or SDMA strongly supports a CKD diagnosis.
Phosphorus and Blood Pressure
Elevated blood phosphorus is both a consequence of CKD and a driver of its progression. Cats with CKD are also prone to systemic hypertension, which can cause sudden blindness if left untreated. Your vet will measure blood pressure and check phosphorus levels at each monitoring appointment.
Understanding IRIS Staging
The International Renal Interest Society (IRIS) has developed a widely adopted staging system for feline CKD. This staging framework, endorsed by ECVIM-CA and referenced in WSAVA guidelines, helps vets make consistent treatment decisions and gives owners a clearer picture of their cat's condition.
- Stage 1: Creatinine below 140 µmol/L; kidney damage is present but function is near normal. Signs may be absent. Early detection via SDMA is particularly valuable here.
- Stage 2: Creatinine 140–249 µmol/L; mild azotaemia. Many cats are clinically stable and can remain so for years with appropriate management.
- Stage 3: Creatinine 250–439 µmol/L; moderate azotaemia. Clinical signs are usually present, and quality of life support becomes central to care.
- Stage 4: Creatinine above 440 µmol/L; severe azotaemia and uraemic signs. Palliation and comfort are the primary goals.
Each stage is further sub-staged based on blood pressure and urine protein levels (proteinuria), which helps tailor treatment more precisely. ESCCAP also recommends integrating parasite screening and dental health checks into the care plan, as both can influence systemic disease in cats with CKD.
Managing CKD: Diet, Fluids and Medication
Renal Diets and Phosphorus Restriction
Nutritional management is the cornerstone of CKD care. Renal diets are formulated to be low in phosphorus, moderately protein-restricted, and palatable enough to encourage a cat with a poor appetite to eat. Multiple studies have shown that renal diets can significantly slow disease progression and extend survival time in cats with Stage 2 and 3 CKD.
Wet food is strongly preferred over dry kibble because its high moisture content supports hydration — a critical factor given that cats with CKD struggle to concentrate urine. Retailers such as Zooplus stock a wide range of veterinary renal foods from brands like Hill's Prescription Diet, Royal Canin Renal, and Purina Pro Plan Veterinary Diets, often at competitive prices for owners buying in bulk over the long term.
Hydration and Subcutaneous Fluids
Keeping a CKD cat well hydrated is essential. Alongside offering wet food, cat water fountains can encourage drinking. In moderate to advanced cases, vets may teach owners to administer subcutaneous fluid therapy at home — a technique that many owners find manageable and that cats typically tolerate well. This can greatly improve a cat's comfort and energy levels between clinic visits.
Phosphate Binders
When dietary phosphorus restriction alone is insufficient to keep blood phosphorus within target range, vets prescribe phosphate binders. These are given with meals and bind dietary phosphorus in the gut before it can be absorbed. Aluminium hydroxide and calcium carbonate are commonly used options.
ACE Inhibitors and Blood Pressure Management
In cats with proteinuria or hypertension, angiotensin-converting enzyme (ACE) inhibitors such as benazepril may be prescribed. These drugs reduce pressure within the kidney's filtering units, helping to slow progression and reduce protein loss in the urine. Anti-hypertensive medication such as amlodipine is used when blood pressure is persistently elevated.
Quality of Life and Prognosis
With consistent management, many cats with Stage 2 CKD live comfortably for several years after diagnosis. Even Stage 3 cats can maintain a good quality of life for an extended period when owners commit to dietary changes, regular monitoring, and any prescribed medications. Regular veterinary check-ups every three to six months allow the care plan to be adjusted as the disease evolves.
When to Seek Urgent Veterinary Attention
Contact your vet promptly or attend an emergency clinic if your cat shows any of the following:
- Sudden loss of vision or apparent blindness (a sign of hypertensive crisis)
- Complete refusal to eat for more than 24 hours
- Profound lethargy or collapse
- Repeated vomiting within a short period
- Severe weight loss over a short timeframe
- Seizures or disorientation
Acute-on-chronic kidney disease — a sudden worsening triggered by dehydration, infection, or medication — is a medical emergency. Prompt intervention can often restore baseline function and stabilise your cat.
CKD is a condition that asks a great deal of both cats and their owners, but with the right knowledge and a good relationship with your vet, many cats navigate it with dignity and comfort for years to come.