Your cat's kidneys perform many important functions. They filter out toxins and waste products in the blood, regulate sodium and vitamin levels, and stimulate red blood cell production. Unfortunately, kidney disease is one of the most common ailments observed in older cats. Thirty percent of cats older than 10 years will develop kidney disease, so it is important for cat owners to know about this condition, including the signs, diagnosis, treatment options, and prognosis for cats with renal disease.
What is kidney disease in cats?
Feline kidney disease is a progressive condition in which the kidneys lose normal function. Cats can develop either acute kidney disease or chronic kidney disease (CKD), and cats with CKD can experience acute kidney disease on top of their chronic condition.
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Acute kidney disease has a sudden onset caused by a specific event, such as illness or injury, while chronic kidney disease usually progresses somewhat gradually as the result of certain diseases or congenital issues. CKD is measured in severity from Stage I to Stage IV (based on guidelines put forth by the International Renal Interest Society, or IRIS).
It is worth noting that the veterinary terminology regarding kidney disease has evolved over time. Clinicians used to refer to kidney disease as kidney failure or renal failure. Currently, the term "kidney disease" is used, as it more accurately describes a decrease in kidney function.
Symptoms of kidney disease in cats
If your cat develops kidney issues, you might notice some or all of the following:
- Weight loss
- Bad breath
- Increased thirst and urination
- Inappetence or nausea
How is kidney disease diagnosed in cats?
Veterinarians use several tools to diagnose kidney disease in cats. Most clinicians will order an SDMA test as part of your cat's routine bloodwork. SDMA can help diagnose Stage I and early Stage II kidney disease. SDMA testing is important because by the time a cat develops clinical signs of renal disease, they are usually already in late Stage II or Stage III. Symptoms normally emerge in Stage II and progress to severe during Stage IV.
Prior to the SDMA test, kidney health was mainly tracked via regular monitoring of blood urea nitrogen (BUN) and creatinine. (Urine specific gravity and urine protein were also used.) But by the time these blood tests show significant increases, a cat has usually already lost 75 percent of kidney function. These tests are now used in combination with SDMA to evaluate kidney function.
Causes of kidney disease in cats
Kidney disease can have many causes, from toxin ingestion to congenital issues. While acute kidney disease often has a directly traceable cause, chronic kidney disease is usually brought on by concurrent disease processes.
Acute feline renal disease causes
- Ureteral or urethral obstruction (when the cat is "blocked" or can't urinate)
- Ingestion of a toxin (antifreeze, toxic plants, etc.)
- Kidney infection
- Feline infectious peritonitis (FIP)
- Heart failure
Risk factors for chronic kidney disease in cats
- Kidney abnormalities present from birth (including polycystic kidney disease)
- Kidney stones or ureteral stones
- Kidney cysts
- Bacterial kidney infections
- Viral infections, such as FIP or feline leukemia virus (FeLV)
- A urinalysis might show the presence of protein
Cat kidney disease stages
IRIS classifies the progressive stages of kidney disease based on clinical signs and renal values obtained from lab work.
- Stage I: Usually has no symptoms; hypertension (high blood pressure) is possible; is normally only detected with SDMA
- Stage II: Mild symptoms start; can be detected with SDMA; slight renal value abnormalities and possibly low potassium
- Stage III: Symptoms become pronounced; bloodwork abnormalities, such as rising phosphorus levels, become apparent
- Stage IV: Symptoms and renal value abnormalities are severe; risk of crisis; end-stage disease
Cats require 25 percent of total kidney function to maintain health. Abnormal electrolyte levels and observable clinical signs can start as early as Stage II, and potassium supplementation might already be needed at this point.
Once a cat has entered Stage III, their kidneys function only between 15 and 25 percent. At this stage, lab tests usually reveal elevated levels of the waste product creatinine (between 2.9 to 5.0), accompanied by abnormal electrolyte values. Cats in Stage III are at risk for gastrointestinal issues, loss of appetite, increased thirst and urination, oral ulcers, anemia, and bladder infections.
Treating Stage III kidney disease in cats
Subcutaneous fluids, the primary treatment for cats experiencing early kidney failure, can be administered at home. Your DVM will teach you how and when to give these fluids. Injected beneath the skin, usually over the shoulder blades, subcutaneous fluids help increase hydration, restore electrolyte balance, and ease the strain on the kidneys by diluting the blood and assisting diuresis.
Depending on your cat's individual needs, your veterinarian might recommend treatment options like an injectable vitamin B-12 supplement, a low-protein kidney diet, anti-nausea medications, omega-3 fatty acids, or appetite stimulants. The goal of treatment for cats in Stage III kidney disease is to prolong survival while maintaining quality of life.
Choosing a Stage IV treatment for cats with renal disease
A cat enters Stage IV kidney disease, or end-stage kidney disease, when their kidneys begin functioning below 15 percent. Laboratory testing reveals creatinine levels above 5.0, usually accompanied by elevated phosphorous levels. Cats in end-stage CKD experience extreme nausea and lethargy, sometimes accompanied by a refusal to eat. Cats in Stage IV kidney disease usually live a few months or less.
At this point, you must consult your veterinarian to determine the best course of action. Intravenous fluids might provide some relief from acute renal failure symptoms and make your cat more comfortable. Your veterinarian also might recommend continuation of medications depending on your cat's response. They might also suggest euthanasia as a humane choice if palliative care can't sufficiently alleviate your cat's symptoms.
Can a cat recover from kidney failure?
Yes, in some cases of acute kidney disease, a cat with no permanent damage can recover. Kidney damage, including damage caused by acute kidney disease, cannot be reversed. However, its progression can be slowed, and you can increase your cat's quality of life and alleviate clinical signs with proper treatment. Cats can usually live many good months with kidney disease and possibly even years if CKD is diagnosed at Stage I. SDMA testing and IRIS staging have greatly increased the possibility of early detection and intervention.
The bottom line
Kidney disease is an unfortunate fact of life for many cats and their owners. While this prolific and progressive condition cannot be reversed, pet owners should know how to spot the symptoms, as early diagnosis and treatment can help prolong and improve the life of a cat with renal disease. It is also helpful for cat owners to know the stages of feline kidney disease as well as the recommended care and treatment for each stage.