Polycystic Kidney Disease in Cats: Symptoms and Care

As PKD causes chronic kidney disease (CKD), the signs and symptoms are exactly the same as CKD, including: 

• Increased thirst and urination, by far the most common early signs
• Weight loss
• Vomiting
• Lethargy
• Poor appetite
• Enlarged abdomen (advanced)
• Bad breath and gum disease associated with high levels of urea in the blood (uraemia)

As we said, many cats won’t show signs until a lot of damage has already been done. With this in mind, it’s very important that you see your vet the moment you notice any of these signs. Early detection is key to the best prognosis. The more you know what is normal for your cat, the sooner you will spot subtle changes in behaviour.

Because cats with PKD present like any other cat with chronic kidney disease, the tests are mostly the same, with genetic testing being an important addition.

Blood & urine tests

These are the most common tests your vet will probably run. There are many diseases whose early signs are increased thirst and urination, such as diabetes, so your vet would probably want to rule these out first. Typically, a full biochemistry and haematology blood panel will be done. For kidney disease, the main blood tests are creatinine, SDMA and blood urea nitrogen (BUN).

When it comes to the urine test, below are some of the tests that vets usually run:

• Urine specific gravity (USG). This is a measure of how concentrated the urine is. One of the main jobs of the kidneys is water preservation. Domesticated cats descended from desert cats, and their kidneys are very good at producing highly concentrated urine. As kidney function is lost, the urine becomes more and more dilute.
• PH. This is a measure of how acidic, neutral or alkaline the urine is. This can be a useful indicator of wider problems and of urinary tract infections (UTIs).
• Microscopy. This checks for inflammatory cells, blood, signs of kidney damage, bacteria infection, crystals and other abnormalities.
• Culture and sensitivity. UTIs are actually quite rare in healthy cats, but as the kidneys fail and the urine becomes more dilute, infections can take hold. Your vet needs to know whether infection is present, and in case it is, what bacteria are involved and which antibiotics will work the best.

Ultrasound

The appearance of polycystic kidneys is very distinctive, especially once it’s in the later stages. Where there should be normal, dense kidney tissue, multiple fluid-filled holes appear in the image instead. You can see the difference between a normal kidney ultrasound and a cat with PKD below.

Genetic testing

Many responsible breeders have undertaken genetic screening of their breeding cats, and this is helping to reduce the incidence of PKD in predisposed cat breeds. However, the disease rate does not decline as quickly as others, and some cats still carry the problematic gene.

If you are thinking about getting any purebred cat, it's recommended that you know what their inherited diseases are and find a breeder that runs the tests and provides proof of the results.

In the early stages of PKD, the vast majority of cats show no signs and have no pain or discomfort. It is the later stages of the disease and the complications it can cause that make the cat feel ill. For example, bladder and kidney infections can occur secondary to the disease and can cause severe pain and depression. Kidney infections (pyelonephritis) can quickly become life-threatening and are an emergency.

The signs of these secondary diseases are quite similar to other conditions such as chronic kidney disease, so be on the lookout for signs such as poor appetite, nausea and vomiting. If you notice anything out of the ordinary, you should contact your vet.

Monitoring and management of cats with PKD is essential to spot complications as soon as they occur, or preferably even before.

Sadly, the bottom line is that polycystic kidney disease is incurable and progressive and causes markedly reduced life expectancy. However, as with CKD, there are treatment and management options that can improve your cat’s quality and length of life.

Nutrition

For all cats with kidney disease, changing to a kidney-supportive food is fundamental to prolonging their life. Renal or kidney support foods feature:

• Reduced overall protein content but high-quality protein. This reduces the work load on the kidneys but still allows your cat to get enough protein to maintain their condition and muscle mass.
• Restricted phosphorus. This is very important and plays a major role in slowing the progression of the disease.
• Restricted sodium, which reduces the burden placed on the kidneys and helps manage blood pressure. 
• High omega-3 fatty acids, which are known to help break the cycle of inflammation.
• Added antioxidants, which help combat cell damage and promote a healthy immune system.

Remember, never start your cat on any food without your vet’s say-so. These foods are not always suitable for cats with other conditions.

In addition to kidney support food, it’s important to ensure your cat stays hydrated. Feeding them wet food or seeing if they will eat kibble soaked in warm water is a great way to get them to consume more fluids. Ensure there are multiple water stations all over the house so that your cat never has to go far for a drink. Many cats love to drink running water, so fountains can be a big help too.

Medications

There are various medications that can help cats with kidney disease. The main ones aim to keep a normal blood pressure to avoid further kidney damage and bind phosphorus in the gut to reduce absorption. The latter may be particularly important if your cat can’t eat a kidney support food for any reason. Your vet may also want to provide drugs for nausea, if your cat is in the later stages, or pain relief. 

Monitoring and vet check-ups

Regular check-ups are critically important. Your vet will guide you as to the frequency of visits and repeat tests depending on your individual cat. This may entail yearly tests if your cat was diagnosed in the early stages by ultrasound or as an incidental finding. Tests are likely to be done every 3-6 months as the disease progresses.

This is incredibly variable and depends on how quickly the cysts grow and develop and how many an individual cat had at birth. It can’t be stressed enough how important early diagnosis and management are for any pet health condition, and this is especially true in the case of kidney disease. The sooner you know it’s there, the sooner your vet can implement measures to slow its progression.

If your cat is diagnosed in the latter stages and is already showing signs of the disease, life expectancy may only be weeks to months, but many cats with PKD can live for years after diagnosis and lead relatively normal lives. In a Japanese study, the average age at death of cats with PKD was 12.7 years. Your vet will be able to give you a better idea of your cat’s life expectancy based on the combined test results for your individual cat.

No pet parent wants to think about losing their beloved pet, but if your cat has a diagnosis of PKD, it’s good to discuss quality of life with your vet early and openly. Many cats live long lives with PKD but end-stage kidney disease is unpleasant. As the disease evolves, it's very important that you, as a pet parent, can recognise whether your cat no longer has a good quality of life. 

Talk to your vet about when they feel it appropriate to draw the line based on the signs of decline your cat presents. Signs of illness can be very subtle in cats, so look for things like:

• Loss of appetite
• Not interacting
• Sleeping all the time
• Not wanting to go out
• Poor coat
• Weight loss

These are all things that might mean the time is right to say goodbye. If you know what to expect, you and your family can be prepared.

Yes, by simply not breeding from affected animals. Sadly, there are many purebred animals afflicted with inherited disease and poor health due to the bodies they have been born into through selective breeding by humans. Responsible breeding is essential, but so is pet choice from prospective pet parents. Always do your research into what diseases a breed suffers from, and talk to a vet rather than simply looking at breed websites.

Never ever buy from a breeder who won’t disclose test results or a breeder who doesn’t test. Even if you’ve already fallen in love with the bundle of fluff!

PKD is a disease with pretty straightforward genetics and a reliable genetic test. Making a responsible choice when getting a cat can encourage breeders to always conduct these tests and greatly help speed up the eradication of this disease.

Polycystic kidney disease in cats is inherited, progressive and incurable. Life expectancy depends on many things and varies widely between cats. With early detection and management, many cats with PKD live for years and have normal lives.

PKD is entirely preventable with routine screening and responsible breeding. Choose your breeders very wisely – or even better, pick a cat that has no breed. Adoption centres are full of cats and kittens waiting for a great home. You get a beautiful friend and you do a good deed at the same time. Everyone’s a winner!

What is polycystic kidney disease in cats

PKD is an inherited, progressive disease where cysts (pockets of fluid) develop in the kidneys over time and destroy the functional kidney tissue, leading to chronic kidney disease and eventually kidney failure.

Is polycystic kidney disease painful for cats?

As a rule, no, but in the latter stages and due to complications such as urinary tract infections, mild discomfort to severe pain may ensue.

Can PKD in cats be cured?

No. PKD is an incurable, progressive disease, but with good management and early diagnosis, many cats live for years after diagnosis.

How long can a cat live with polycystic kidney disease?

This depends on the stage and severity. Some cats may only have weeks to months if they are already in kidney failure, others may live for years after diagnosis. Some cats also have PKD that progresses more quickly than others.

How is polycystic kidney disease diagnosed in cats?

Through blood and urine tests, ultrasound imaging of the kidneys and genetic tests.

Which cat breeds are most affected by PKD?

• Persian 
• Exotic shorthair
• Scottish fold
• Himalayan
• British and American shorthair
• Birman

Can polycystic kidney disease be prevented?

Yes, through genetic screening of breeding cats and responsible breeding. Once a kitten is born with the condition, it’s too late.

Reviewed by Becky Mullis, DVM, DACVIM (Nutrition).