Chronic kidney disease (CKD), commonly called kidney failure, is one of the most common diseases of older cats: an estimated 30–40 % or more of cats over 10 years old have some degree of kidney disease, most of it still mild. In dogs it is much rarer, and most cases are in dogs over 10–12 years. The kidneys lose function slowly and irreversibly, and the first signs are easy to miss. But kidney failure is not an immediate death sentence — with early diagnosis, the right diet and treatment, many cats live for years and dogs for many months to years with a good quality of life. This article explains how to recognise the symptoms, what the IRIS stages mean, how we treat kidney patients at Saari Animal Clinic, what to feed, and what to expect.
What are the symptoms of kidney failure in dogs and cats?
The earliest signs are subtle: the pet drinks more and urinates more (the litter box gets wet faster, the dog asks to go out more often), appetite drops a little and weight creeps down. As the disease progresses the signs become clearer: vomiting, diarrhoea or constipation, a dull, unkempt coat, muscle wasting, lethargy, bad breath with an ammonia-like smell, pale gums from anaemia and mouth ulcers. Cats often just become quieter, hide more and stop grooming. Because the changes come on over months, owners frequently notice them only when two thirds of kidney function is already gone — which is why we recommend a yearly blood and urine test for pets over 7. In cats, weight loss can be measurable years before diagnosis, and a third of cats show no signs at all when the disease is found in a blood test.
What causes kidney failure in dogs and cats?
Chronic kidney disease is usually a slow wearing-out of the kidney tissue with age, and often no single cause is found. Known contributors are high blood pressure, kidney infections and stones, and hereditary conditions such as polycystic kidney disease in Persian and related cat breeds; dental disease is also linked with kidney disease in both species, although it has not been proven to cause it. Acute kidney failure is different: it strikes suddenly, at any age, after a toxin or infection — antifreeze (ethylene glycol), grapes and raisins in dogs, lilies in cats, overdoses of human painkillers such as ibuprofen, leptospirosis, or a septic condition such as pyometra. Acute failure is an emergency: treated quickly, the kidneys can often recover, but not always — roughly half of severe cases are lost — whereas chronic failure cannot be reversed, only slowed.
How is kidney disease diagnosed?
Diagnosis is made from blood and urine. The blood test measures creatinine, urea (BUN), phosphorus and potassium, and at our clinic also SDMA — a marker that rises when about 40 % of kidney function is lost, months to years before creatinine does. The urine test shows whether the kidneys can still concentrate urine (specific gravity) and whether protein is leaking (UPC ratio). We measure blood pressure, because high blood pressure both results from and worsens kidney disease, and an abdominal ultrasound shows the size and structure of the kidneys and looks for stones, obstruction or tumours. A single raised value is not a diagnosis: the stage is set from tests taken on at least two occasions in a stable, well-hydrated patient, which is why we often repeat the blood test after a few weeks before naming the IRIS stage that guides treatment.
What are the IRIS stages of kidney disease?
The International Renal Interest Society (IRIS) classifies chronic kidney disease into four stages by blood creatinine and SDMA. Stage 1: creatinine normal, but some other kidney abnormality is present — a persistently raised SDMA, dilute urine (in cats), protein in the urine, or changes on ultrasound. Stage 2: mild disease; creatinine normal or slightly raised, symptoms usually mild or absent, perhaps only increased drinking. Stage 3: moderate disease; symptoms such as poor appetite, vomiting and weight loss are common but not always present. Stage 4: severe disease with a high risk of uraemic crises — nausea, mouth ulcers, weakness. Each stage is further sub-staged by blood pressure and urine protein. The stage determines what treatment is started and how often we re-check.
How is kidney failure treated?
Kidney disease cannot be cured, but its progression can often be slowed considerably. The cornerstones are a renal diet with restricted phosphorus and moderate high-quality protein (shown in clinical studies to extend survival), phosphate binders when phosphorus stays high, plenty of water and — when needed — fluid therapy, either intravenously at the clinic or, for selected patients, under the skin at home after we have taught you the technique and with regular checks, because too much fluid can be harmful (especially in cats with heart disease), blood-pressure medication once the patient is stable and hydrated (amlodipine for cats, ACE inhibitors or telmisartan when protein leaks into the urine), anti-nausea and appetite medication, potassium supplements and, in advanced anaemia, a hormone injection (darbepoetin) to stimulate red blood cell production. Urinary infections are treated promptly, because in a kidney patient they can spread to the kidneys, and dental disease is kept under control. At Saari we build an individual plan for each kidney patient and adjust it at every check-up.
What should a dog or cat with kidney failure eat?
A therapeutic renal diet is the treatment with the best evidence behind it: in studies, cats that ate a renal diet lived around twice as long as cats that did not (median 633 versus 264 days in one study), had far fewer uraemic crises in a randomised trial, and dogs benefited at least as much (594 versus 188 days). Renal diets are low in phosphorus, have moderate amounts of high-quality protein, added omega-3 fatty acids, potassium and B vitamins, and are less acidifying. Wet food is preferable because it carries water into the patient — many kidney patients are chronically slightly dehydrated. Start the renal diet early — ideally in stage 2, while appetite is still good — and never while the pet is ill, nauseous or hospitalised, because a food eaten during nausea is often refused for good afterwards. For the same reason, never hide tablets in the renal food — use a separate treat. Change food gradually over several weeks (in cats often 4–8 weeks), mixing old and new, and never force a renal diet on a pet that refuses it; eating something is more important than eating the perfect food, and we have several brands and flavours to try. Home-cooked kidney diets are possible but must be formulated by a veterinary nutritionist — an unbalanced home diet does more harm than good. Ask us about renal foods; we also sell them at the clinic.
How long can a dog or cat live with kidney failure?
It depends mostly on the stage at diagnosis and on how well phosphorus, blood pressure and appetite are controlled. Cats generally do better than dogs: in the largest study with survival by stage, cats diagnosed at the upper end of stage 2 lived a median of about 3 years, in stage 3 about 2 years, and in stage 4 about 3 months — cats caught earlier in stage 2 can be expected to do better. In dogs the disease tends to progress faster — in a smaller study, dogs in stage 2 lived a median of over a year, in stage 3 several months to a year, and in stage 4 weeks to a few months. These are median values from published studies of treated animals — half of the animals lived longer than these figures — not predictions for your pet: with a well-accepted renal diet, good appetite and regular monitoring, individual animals frequently outlive them.
What does end-stage kidney failure look like?
In the final stage the kidneys can no longer clear waste from the blood, and the pet becomes uraemic: it refuses food and water, vomits, loses weight rapidly, is weak and sleeps most of the day, may have mouth ulcers, a strong smell on the breath, and occasionally tremors. Fluids, anti-nausea drugs and appetite stimulants can bring good days back for a while, and we help you judge quality of life honestly: is the pet still eating, moving, interacting and free of pain most days? When the answer becomes no, euthanasia is the last kindness we can offer, and we talk about it with you openly and in time.
How often should a kidney patient be checked?
After diagnosis we usually re-check within 2–4 weeks to see how the diet and treatment are working, then every 3–6 months in stable stage 2 patients, every 2–3 months in stage 3, and every 1–2 months in stage 4. Each check includes weight, blood pressure, a blood test (creatinine, SDMA, phosphorus, potassium, red blood cells) and a urine test. Regular monitoring is what lets us adjust treatment before a small problem becomes a crisis.
Can kidney disease be prevented or caught early?
Chronic kidney disease cannot be fully prevented, but it can be caught early — and treatment started in stage 2 gives the best chance of slowing it down. We recommend a yearly senior check with blood and urine tests for dogs and cats over 7 (our senior check-up includes an SDMA kidney test), keeping teeth healthy (dental disease is linked with kidney disease), feeding wet food to cats that drink little, and keeping antifreeze, human painkillers, grapes and lilies out of reach. Have a cat that is drinking more or losing weight checked without delay — these are the usual first signs, although a third of cats show nothing at all until the blood test.
When should I bring my pet to the vet?
If your dog or cat drinks and urinates more than before, has lost weight or appetite, vomits repeatedly or has bad breath — book an appointment. A blood and urine test taken at the visit shows whether the kidneys are involved; to confirm chronic kidney disease and set the stage we usually repeat it once the pet is stable. Saari Animal Clinic in Vaasa follows kidney patients on an individual schedule; call (06) 321 7300 or book online.
Sources
- International Renal Interest Society (IRIS): IRIS Staging of CKD and treatment recommendations. iris-kidney.com
- Sparkes A.H. ym. (2016): ISFM Consensus Guidelines on the Diagnosis and Management of Feline Chronic Kidney Disease. Journal of Feline Medicine and Surgery 18(3):219–239. doi.org
- IDEXX: SDMA and IRIS — early detection and staging of chronic kidney disease. idexx.com
- Elliott J. ym. (2000): Survival of cats with naturally occurring chronic renal failure — effect of dietary management. Journal of Small Animal Practice 41(6):235–242. doi.org
- Ross S.J. ym. (2006): Clinical evaluation of dietary modification for treatment of spontaneous chronic kidney disease in cats. Journal of the American Veterinary Medical Association 229(6):949–957. avma.org
- Boyd L.M. ym. (2008): Survival in cats with naturally occurring chronic kidney disease (2000–2002). Journal of Veterinary Internal Medicine 22(5):1111–1117. doi.org
- O'Neill D.G. ym. (2013): Chronic kidney disease in dogs in UK veterinary practices: prevalence, risk factors, and survival. Journal of Veterinary Internal Medicine 27(4):814–821. doi.org
- Jacob F. ym. (2002): Clinical evaluation of dietary modification for treatment of spontaneous chronic renal failure in dogs. Journal of the American Veterinary Medical Association 220(8):1163–1170. doi.org