Kidney disease in cats is alarmingly common, affecting approximately 40% of all cats at some point in their lifetime. It’s also one of the leading causes of death in cats. If we’re lucky enough for our cats to live past the age of 15 years, there’s an 80% chance that these senior kitties will eventually experience some kind of health issues with their kidneys.
Although kidney disease (also called renal disease) can develop at any age, it’s much more common in older cats. Because the kidneys play such an important role in the body, changes in the kidneys can have a great impact on many other bodily systems as well.
Kidney disease in cats comes with the classic “good news, bad news” scenario. First, the bad news: classic signs of kidney disease do not show up until about 75% of kidney function has already been lost, and once this damage has occurred, it’s irreversible. This makes diagnosing and treating kidney disease extremely difficult and frustrating, especially for veterinarians.
But there is also good news: with proper care and treatment, many cats who are diagnosed with kidney disease can do well for up to several years after diagnosis.
How Do Kidneys Work?
The kidneys have 5 main functions:
- Filtering waste products and extra water from the blood, which eliminates toxins from the body and maintains a proper level of hydration.
- Regulating electrolytes (such as sodium, potassium, phosphorous, and calcium) in the body.
- Producing and concentrating urine, which is made up of waste, toxins, and extra fluid that the body doesn’t need.
- Producing erythropoietin, a hormone that stimulates the bone marrow to create new red blood cells.
- Producing renin, an enzyme that controls the body’s blood pressure.
As blood flows through the kidneys, approximately 200,000 microscopic structures called nephrons perform an intricate filtering job that removes toxins from the blood and keeps beneficial substances (such as serum proteins) circulating in the bloodstream. These toxins become part of the urine, which is then efficiently eliminated.
How Kitty Kidneys Get Into Trouble
In young, healthy cats, there are so many nephrons available that not all are needed; some are kept in reserve, on stand-by mode. As cats age, or if the kidneys become damaged, nephrons begin to die off, and the reserve nephrons take over. Eventually however, at some point, all the nephrons that are able to function will be functioning, with none left as back-up.
Any damage or loss of nephrons that occurs after that point overloads the remaining nephrons. When this happens, waste products and toxins can no longer be filtered as effectively, and they begin to accumulate in the cat’s body. The kidneys become further stressed and are not able to perform their primary functions, leading to electrolyte imbalances, blood pressure issues, and anemia. As kidneys continue to deteriorate, they can no longer conserve water effectively, and the cat begins to pass larger amounts of dilute urine.
Only after all this has occurred do these overloads on the body begin to create the classic signs of kidney failure. Sadly, by the time kidney disease symptoms show up, about 75% of all nephrons have already been lost.
Chronic vs. Acute Kidney Failure
The above scenario represents chronic kidney failure (CKF), which happens over a long period of time, usually over several years.
There is another form of kidney failure, acute kidney failure, that can happen suddenly and in cats of any age. Acute kidney failure can be caused by:
- Ingesting toxins, such as antifreeze (ethylene glycol), or eating certain toxic houseplants
- Kidney infection
- Severe dehydration
- Shock caused by trauma or blood loss
- Stress from surgery
- Adverse reactions to medication
- Becoming “blocked” (where urine is unable to exit the body because of an obstruction)
Although damage caused by acute kidney failure may be permanent, in many cases it can be completely reversible with prompt and proper treatment. Acute kidney failure is extremely serious and can quickly become fatal, so immediate veterinary treatment is critical.
Signs Of Kidney Disease In Cats
Signs of kidney disease can vary quite a bit from one cat to another. They can be subtle and difficult to notice, or severe and alarming. However, one of the most frustrating aspects of kidney disease is that the early stages often show no signs whatsoever, while other symptoms can mimic those of hyperthyroidism or diabetes.
The most common signs of kidney disease in cats include:
- Vomiting (both food and clear or foamy liquid)
- Decreased appetite
- Increased urine output (“flooding” the litter box), or producing very little urine or no urine at all (two extremes)
- Increased thirst
- Weight loss
- Sleeping more than usual
- Unusual odor to the breath
- Lethargy (no energy)/weakness/depression
Other, more subtle, signs may include:
- Leaking urine (especially while sleeping)
- Dry gums (from dehydration)
- Licking lips and/or gagging (signs of nausea)
- Pale gums (indicates anemia, caused by the body not producing enough red blood cells)
- Dull or dry hair coat
- Mouth ulcers
- Eye problems, such as broken blood vessels in the eye or blindness (associated with high blood pressure)
Since only 25-30% of kidney capacity is needed for normal functioning, cats may show no symptoms until almost 75% of kidney function is completely lost. Therefore, it’s important to have your cat examined by a veterinarian immediately if you suspect kidney problems. Cats who progress to end-stage kidney failure often have seizures and a very low body temperature, and will eventually fall into a coma. That’s why it’s critical to get treatment as soon as you notice anything unusual, especially if your cat is older.
Diagnosing Kidney Disease In Cats
To determine the extent of a cat’s kidney damage, veterinarians usually start with a blood test (which measures kidney function, electrolyte balance, and the number of red blood cells), and a urinalysis (which checks to see if urine is too dilute, indicating the kidneys are not filtering waste properly).
The veterinarian may also recommend one or more of the following tests:
- X-rays or ultrasound (to identify changes in the size or shape of kidneys)
- Blood pressure measurement (since high blood pressure is common with kidney disease)
- Thyroid testing (hyperthyroidism can mimic kidney disease)
- Kidney biopsy
There is also a promising new test that may help identify kidney disease in cats before most permanent damage occurs – an average of 17 months earlier than other tests. This test is manufactured by IDEXX, and run with a blood sample. For more information, ask your veterinarian.
Management Of Kidney Disease
Acute kidney failure is an emergency, and must be treated immediately with intravenous solutions administered by your veterinarian. If treated in time, most cases of acute kidney failure can be successfully reversed.
Unfortunately, there is no real cure for chronic kidney failure. However, depending on the severity of the condition, it can be successfully managed for anywhere from several months up to several years.
Management goals for cats with chronic kidney disease include controlling the buildup of waste products in the bloodstream, delaying loss of further kidney function, and maintaining a good quality of life for the cat for as long as possible.
This is usually done through the use of:
This involves home therapy, with cat parents injecting the cat with fluids under the skin (subcutaneously), in the area between the shoulder blades, as needed. Although it’s intimidating at first, with a little practice, cat parents quickly become professionals at doing it, and most cats handle it very well.
Cats can also be encouraged to drink more water on their own with the use of water fountains, as well as keeping several water dishes around the home in various locations. Increased water going into the cat’s body helps flush out accumulated toxins, and makes the cat feel much better.
Wet, or canned, food is much better than dry food for cats with kidney disease (and truly, for most cats in general) due to its increased moisture content.
Most veterinary nutritionists also recommend a diet that includes very high-quality protein sources and lower than normal amounts of sodium and phosphorous.
Medications can be given to lower the phosphorous level in the bloodstream if it’s too high, as well as to treat other medical conditions that can occur because of compromised kidneys, including high blood pressure and anemia.
As a last resort, kidney dialysis and kidney transplants are also available for feline patients; however, for the vast majority of people, these options are extremely cost-prohibitive. They are also still not considered a cure for the disease.
Early Detection Is Key
Kidney disease is one of the leading causes of illness and death in cats, and sadly, there is no cure. For a cat with kidney disease, the question becomes how long she will live, and what her quality of life will be for the remainder of her time.
Fortunately, if kidney disease is detected in its early stages, it can be successfully managed – giving many cats a good quality of life for several years after diagnosis. As long as they are kept well-hydrated (keeping toxins flushed), fed a diet that eases any burden on the kidneys, and kept in good health, many of these cats are able to live comfortably until their kidneys are no longer able to function.
Since the chance of developing kidney problems increases in cats over the age of 7 years, it’s a good idea to screen cats age 7 and older for kidney disease during their annual exam. Early detection can allow your veterinarian to take the proper measures well before your cat starts showing signs of kidney disease, when most of the damage has already been done.
Have you ever cared for a cat with kidney disease? Please share your story with us in the comments below!