Health guide · Cat · Renal / Chronic

CKD / CRF

Chronic Kidney Disease in cats

Chronic kidney disease (CKD) is one of the most common conditions in senior cats. It progresses slowly and silently, but proper management can offer years of good quality of life.

Definition

What is chronic kidney disease?

CKD is a progressive and irreversible deterioration of the kidneys. When more than three-quarters (about 75%) of nephrons (filtering units) are damaged, the body can no longer effectively clear waste, which then builds up in the blood: this is azotemia (elevated urea and creatinine). The disease primarily affects middle-aged to senior cats and progresses silently, often detected late without regular checkups.

50%

of cats over 15 years old are affected

Common

one of the most common chronic diseases in senior cats

+17 months

earlier on average with the SDMA marker

Several years

of survival possible with proper management

The 4 key kidney functions

Waste filtration

Removal of blood urea nitrogen (BUN), creatinine, and other metabolic waste products from the bloodstream.

Blood pressure regulation

Control of blood volume and arterial pressure via the renin-angiotensin system.

Erythropoietin production

Secretion of the EPO hormone that stimulates red blood cell formation in the bone marrow.

Fluid and electrolyte balance

Regulation of water, potassium, sodium, and phosphates throughout the body.

CKD is distinct from acute kidney injury (AKI), which occurs suddenly following trauma, poisoning, or severe infection. Both forms can coexist in the same animal.

Clinical signs

Signs and symptoms

CKD often progresses silently. Early signs are subtle and frequently attributed to normal aging. Learning to recognize them early can change the course of the disease.

Early stage

Often mistaken for normal aging

•Fatigue, prolonged sleep
•Progressive muscle loss, stiff gait
•Mild to moderate weight loss
•Loss of appetite, mild nausea
•Occasional vomiting or diarrhea

Intermediate stage

Consult your veterinarian

•Increased thirst and urination (polyuria/polydipsia), often the first change owners notice at home
•Withdrawal, quieter behavior
•Ammonia-smelling breath (uremic halitosis)
•Unkempt coat, reduced self-grooming

Advanced stage

Urgent consultation recommended

•Sunken eyes, severe dehydration
•Oral ulcers (gums, tongue)
•Excessive drooling and oral discomfort (uremic mouth ulcers)
•Unsteady gait (ataxia), marked weakness
•Nighttime vocalizations, disorientation
•Seizures (with very severe uremia: the body being poisoned by waste build-up)

Emergencies

When to seek immediate care?

These signs indicate acute renal decompensation or a serious complication requiring immediate veterinary care.

Open-mouth breathing or panting, respiratory distress (cats rarely pant, so any panting is an emergency)
Inability to move, sudden collapse
Seizures or tremors
Sudden blindness or abnormally wide, fixed pupils, cat bumping into objects (hypertensive emergency: prompt blood-pressure treatment can preserve vision)
Complete refusal to eat for more than 24 to 48 hours (a cat that stops eating deteriorates rapidly)
Sudden drop or absence of urine output, or repeated straining to urinate with no result
Uncontrollable vomiting or diarrhea
Prostration, unresponsive to stimuli
Vocalizations of intense pain

In an emergency, contact your veterinarian or an emergency clinic immediately.

Diagnosis

How is the diagnosis made?

Many cats with CKD show no clinical signs in the early phase. Regular checkups starting at age 7 are the best way to detect the disease before symptoms appear.

SDMASDMA (symmetric dimethylarginine) is a simple blood test that can reveal kidney damage up to 17 months before the older marker, creatinine, when only 25 to 40% of kidney function has been lost. It is now the most sensitive marker for early feline CKD screening, used alongside creatinine, which remains the basis for staging.

Blood tests

BUN (blood urea nitrogen) and creatinine levels to assess azotemia. SDMA is a more sensitive marker detecting kidney function loss much earlier. Complete panel including electrolytes, phosphorus, potassium, and blood count (anemia).

Urinalysis

Urine specific gravity: failing kidneys concentrate urine less and less well (isosthenuria), which is why the cat drinks and urinates more. This is an important early sign. Assessment for protein in the urine (proteinuria), quantified by the urine protein-to-creatinine ratio (UPC): protein leakage worsens prognosis. Also screening for abnormal cells, crystals, and bacteria.

Imaging

Abdominal X-rays to evaluate kidney size and shape. Ultrasound to examine kidney structure, detect cysts (polycystic disease), kidney stones, or focal lesions.

Additional tests

Urine culture to rule out underlying infection. Blood pressure measurement (hypertension is frequent). Active screening for comorbidities: hyperthyroidism, dental disease, heart disease, whose management can slow kidney progression.

Treatment

Treatment and management

CKD is not curable, but it is manageable. The goal is to slow progression, support remaining kidney function, and ensure the best possible quality of life. A personalized plan, regularly adjusted, is essential.

Renal diet

Wet food (cans): promotes natural hydration and reduces kidney workload.
Low phosphorus: reduces hyperphosphatemia, which accelerates kidney damage.
High-quality protein, controlled amount: limits nitrogenous waste production without causing malnutrition.
Omega-3 fatty acids (EPA/DHA): already built into most renal foods; an anti-inflammatory effect that may help slow progression. Do not add a supplement without veterinary advice.
Switch very gradually: introduce the new renal food over 2 to 4 weeks (roughly 10% more each day). Cats readily develop a lasting aversion if their food is changed abruptly or during a bout of nausea, so start the new diet only once your cat is stable and eating well.
Veterinary prescription: renal foods (Hills k/d, Royal Canin Renal, etc.) meet strict criteria; do not substitute without advice.

Hydration

Water fountains: encourage voluntary drinking and reduce urine concentration.
Exclusive wet food: provides 70 to 80% of required water directly through food.
Subcutaneous fluids at home: technique taught by the veterinarian for advanced stages; prevents dehydration crises.
Periodic hospitalizations: intravenous fluid therapy during acute decompensations.

Medications and supplements

Blood pressure control: amlodipine (a calcium-channel blocker) is the first-line treatment for feline hypertension. It is started when systolic pressure stays high (generally above about 160 mmHg), to protect the eyes, heart, and brain.
Kidney protectors (RAAS blockers): telmisartan and benazepril mainly reduce proteinuria and also help control blood pressure; they are introduced cautiously, with monitoring of kidney values and potassium.
Phosphate binders: lanthanum carbonate, chitosan (Ipakitine), calcium carbonate: reduce intestinal phosphorus absorption. Give with or just before meals to bind dietary phosphorus; taken away from food they are largely ineffective. Calcium-based binders require blood calcium monitoring.
Potassium supplement: some cats with CKD lose too much potassium in their urine, causing muscle weakness and sometimes a lowered head and neck; when bloodwork shows this, a supplement (potassium gluconate or citrate) is prescribed. Citrate also helps correct the metabolic acidosis seen in advanced stages.
Anti-nausea / appetite stimulants: maropitant, mirtazapine, ondansetron to maintain adequate food intake.
Anemia treatment: recombinant erythropoietin, darbepoetin, iron supplements based on severity.

Comorbidities and follow-up

Hyperthyroidism: must be managed carefully (risk of unmasking underlying CKD); close kidney monitoring after treatment.
Urinary tract infections: culture and targeted antibiotherapy; untreated infections accelerate deterioration.
Dental disease: source of chronic inflammation that can worsen kidney progression.
Regular monitoring: blood and urine panels every 3 to 6 months to continuously adjust treatment.

Prognosis

IRIS stages and prognosis

The IRIS (International Renal Interest Society) system classifies CKD into 4 stages, primarily based on plasma creatinine. SDMA is a supportive marker, useful for detecting the disease earlier and for reassessing the stage when creatinine underestimates kidney damage (for example in a thin or low-muscle cat). The stage guides therapeutic decisions and provides an indication of long-term prognosis.

Stage 1

Asymptomatic

Creatinine: < 140 µmol/L (< 1.6 mg/dL)SDMA: < 18 µg/dL

No measurable azotemia. Detected only via SDMA or urinalysis. Excellent prognosis with early management: several years of good quality of life are achievable.

Stage 2

Mildly azotemic

Creatinine: 140 to 250 µmol/L (1.6 to 2.8 mg/dL)SDMA: 18 to 25 µg/dL

Clinical signs often absent or subtle. The vast majority of cats respond well to treatment and maintain good quality of life for 2 to 5 years or more.

Stage 3

Moderately azotemic

Creatinine: 251 to 440 µmol/L (2.9 to 5.0 mg/dL)SDMA: 26 to 38 µg/dL

Clinical signs present and often significant. Intensified treatment. Median survival of 1 to 3 years with good management. Quality of life can be preserved with rigorous follow-up.

Stage 4

Severely azotemic

Creatinine: > 440 µmol/L (> 5.0 mg/dL)SDMA: > 38 µg/dL

Severe uremia, risk of uremic crises. Survival is often weeks to a few months, though every cat is different. The priority becomes comfort: palliative care at home to keep your cat at ease. If quality of life declines despite care, euthanasia may be considered gently. The decision is yours, and our team supports you through every step.

IRIS substaging: whatever the stage, each cat is also classified by proteinuria (urine protein-to-creatinine ratio, UPC: normal < 0.2; borderline 0.2 to 0.4; proteinuric > 0.4) and by systolic blood pressure. Proteinuria and hypertension worsen the outlook at any given stage and guide treatment; their interpretation is for your veterinarian.

Good news: the stage is not a fixed sentence. Prognosis also depends on treatable factors (blood pressure, anemia, protein leakage), response to treatment, and how early care begins. A well-managed Stage 3 cat can do better than a Stage 2 cat whose hypertension is left uncontrolled.

Home care

Improving daily comfort

Raised, easily accessible food and water bowls

Filtered or fresh water, changed daily

Water fountain to encourage drinking

Kidney-adapted wet food (veterinary prescription)

Quiet, warm, secure resting places

Multiple clean litter boxes, easily accessible (no stairs if possible)

Subcutaneous fluids at home

For cats in Stage 3 or 4, administering subcutaneous fluids at home (for example 100 to 150 ml, 2 to 3 times per week, as prescribed by your veterinarian) can significantly improve their comfort and reduce hospitalizations. Your veterinarian will train you on the technique and set the volume suited to your cat. Most cats tolerate it well and many owners grow comfortable after a demonstration. Every pair is different: if you or your cat find it too hard, please tell us. It is not a failure, and there are other options (fluids at the clinic, adjusting the plan).

Active disease management

Give the prescribed medications as agreed (antihypertensives, phosphate binders, etc.); if your cat refuses them, especially because of nausea, contact us rather than forcing it: we can adjust the form, the timing, or add an anti-nausea medication

Make care low-stress: hide pills in a treat or a lickable paste, warm subcutaneous fluids to body temperature (cold fluids are uncomfortable), go gently and stop if your cat is distressed, then reward after each session

Monitor appetite, water intake, and urine volume every day

Weigh your cat weekly (tip: step on a bathroom scale holding your cat, then without: the difference is their weight): sudden weight loss is a warning sign

Check hydration: dry or tacky gums are the most reliable sign at home; a fold of skin on the scruff that stays tented is a secondary clue, less reliable in a thin or older cat. If in doubt, call us rather than adjusting fluids on your own

Control stress: avoid sudden changes, loud noises, unsupervised new animals

Regular veterinary visits (every 3 to 6 months minimum) to continuously adjust treatment

Adapted enrichment: gentle toys, perches, calm interaction; avoid intense exercise when the cat is weak

Maintain a stable routine and accessible quiet spaces at all times

Never do

Never give human or over-the-counter medication or an anti-inflammatory (NSAID: ibuprofen, aspirin, meloxicam) without a prescription: risk of acute kidney failure. Acetaminophen (Tylenol) is lethal to cats.
Never restrict access to water: a cat with CKD urinates heavily and dehydrates quickly, so water must stay available at all times.
Never switch food abruptly: introduce the renal diet gradually over 2 to 4 weeks, especially if the cat is nauseous or just out of hospital, to avoid food aversion.
Never stop a prescribed medication because the cat seems to feel better, without checking with us first.
Never dismiss weight loss or reduced appetite as normal aging.

Tracking quality of life day to day

A simple tool: keep a good-days-versus-bad-days journal. Each day, note whether your cat ate on its own, moved comfortably, sought your company and still enjoyed its usual routines. When bad days start to outnumber good ones, tell us: together we will assess quality of life using a validated scale.

Monitor every day

Appetite and food intake

Urine volume and appearance

Stools (frequency and consistency)

Weight and energy level

FAQ

Frequently asked questions

How can CKD be detected before symptoms appear?

The SDMA marker can detect kidney function loss when only 25 to 40% of renal capacity is gone, approximately 17 months before creatinine levels rise. Annual blood panels including SDMA starting at age 7 is the best early screening strategy. Urine specific gravity is another early indicator: dilute urine can signal CKD even before blood markers rise.

My cat has both hyperthyroidism and CKD: which to treat first?

This is a delicate question. Hyperthyroidism increases renal blood flow and can mask CKD: creatinine may appear normal despite underlying kidney failure. Treating hyperthyroidism without closely monitoring the kidneys can reveal CKD that seemed absent. Current recommendation: start hyperthyroidism treatment gradually and recheck kidney values (creatinine, SDMA, phosphorus) roughly every 2 to 4 weeks during dose adjustment, then again once euthyroidism is achieved. It is mainly after thyroid levels normalize, over the first few weeks to a few months, that previously masked CKD may become apparent.

Do I really need to give subcutaneous injections at home?

Not necessarily, but for cats in advanced stages, home subcutaneous fluids often significantly improve comfort and reduce hospitalizations. The technique is taught by the veterinarian and tolerated well by most cats. Many owners, even without medical experience, grow comfortable after a demonstration; if it stays too hard for you or your cat, tell us, other options exist. If your cat is in Stage 3 or 4, discuss this option with your veterinarian.

My CKD cat has a poor appetite; how do I help maintain weight?

Loss of appetite is one of the most challenging complications to manage. Effective strategies: gently warm food (releases aromas), offer several small meals instead of two large ones, try different renal food textures and flavors. Appetite stimulants such as mirtazapine (tablet or transdermal gel) or capromorelin can be prescribed. The anti-nausea drug maropitant helps when nausea is present. If appetite remains inadequate despite these measures, ask us about an esophagostomy feeding tube: often well tolerated, it makes feeding, hydration, and giving medications easier while reducing the stress of care. Never switch back to non-renal food without veterinary advice.

Is CKD hereditary? Could my other cat develop it?

Certain breeds have a genetic predisposition: Persians and Himalayans are predisposed to polycystic kidney disease (PKD), a hereditary form of CKD detectable by ultrasound or DNA test. Siamese and Abyssinians also show a slight predisposition. That said, the vast majority of feline CKD cases are idiopathic (unknown cause) or age-related. Regular screening of all cats over age 7 remains recommended regardless of breed.

When does euthanasia become the most humane decision?

Terminal CKD manifests as complete anorexia, extreme weakness, seizures, disorientation, and inability to enjoy anything. It is normal to dread this moment and to grieve, sometimes well before it comes: these feelings are valid. Until then, comfort care can preserve good days. When your cat no longer eats, cannot move comfortably, and appears to be suffering despite care, euthanasia can be the kindest choice, the one that ends the suffering. It is a deeply personal decision: a good-days-versus-bad-days journal (see Home care) helps make it objective, and together we will assess quality of life using a validated scale. When the time comes, we ensure a gentle, respectful process, and you can stay with your cat, before, during, and after.

Your senior cat deserves regular kidney screening.

Early detection can make all the difference. Our team is here to support you at every stage of your cat's kidney disease.

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