Autosomal dominant polycystic kidney disease (AD-PKD)

Autosomal dominant polycystic kidney disease (known as AD-PKD) is an inherited condition that can cause severe kidney failure in cats. The disease causes small, fluid filled holes (cysts) to form in the kidney, and these gradually get larger as the cat gets older. As the cysts get bigger the kidneys are unable to work normally and kidney failure will eventually occur, but the time course of this is very variable.

The disease is caused by an abnormal gene. All cats with the abnormal gene will develop the disease but because the signs of disease usually do not develop until the cat is adult it is possible for a cat to breed extensively (and pass the disease on to its kittens) before the affected cat becomes ill. It is therefore essential to screen breeding cats of high risk breeds for the presence of the gene before they are used for breeding.

Cats with PKD have progressive kidney disease that will ultimately lead to kidney failure. The disease cannot be treated but if your cat does develop renal failure, there are some treatments that may help to improve its quality of life. Sadly the disease is ultimately fatal. The only way to prevent future cats suffering the same fate is to make sure that affected cats are not allowed to breed.

PKD is an inherited disease passed from parents to offspring in the genes. The affected gene is an autosomal dominant gene, so it affects both males and females; only one of the parents needs to have the disease for it to be passed onto some of the kittens, and all cats that inherit even a single copy of the affected gene will be affected by PKD.

PKD is a very rare condition in breeds other than those that are, or are related to, Persians and Exotic shorthairs. Persian cats throughout the world appear to have an especially high chance of having PKD. Recent figures show that 1/3 of Persians cats in the UK are affected, and numbers are similar throughout the world.

Other breeds, related to Persians, are also at high risk of the disease. The disease is common in Exotic shorthairs, with 3 in 10 testing positive for PKD. Other breeds which may have imported the PKD gene through previous outcrosses with Persian cats include British shorthairs, Burmillas and possibly Maine Coons.

Cats can be screened for the presence of disease before they start to show signs of kidney failure. Breeding cats from the high-risk breeds should be screened for AD-PKD before they are used for breeding. If your cat belongs to one of the breeds at risk of AD-PKD then it may well have come with some sort of certification from the breeder and if both its parents are free of the disease then it will not have disease.

If your cat is in a high-risk breed group and its parents have not been tested then you can arrange for a gene test to be done. The test uses DNA extracted from a swab taken from inside the cat’s mouth, or from a blood sample. Cats over 10 months of age can also be screened for the disease by ultrasound scanning.

The gene test for ADPKD involves collections of cells from the cat’s mouth, or from a blood sample. The sample is then sent to one of the accredited laboratories offering the gene test. There are two accredited laboratories in the UK (Langford Veterinary Diagnostics and the Animal Health Trust) and many breeders also use the lab in the USA where the test was developed (Veterinary Genetics Laboratory, University College, Davis, California).

In order to qualify for entry on the AD-PKD Negative Register cats must also have an identification microchip, the number of which must be recorded by a vet on the submission form which accompanies the sample to the lab.

Ultrasound scanning can be used to identify the kidney cysts. If the cysts are large they can easily be identified by routine scanning (just like pregnancy testing in humans) and this is useful in cats with advanced PKD, e.g. those that have enlarged kidneys, or that have already developed renal failure. A small patch of fur will need to be clipped so that the ultrasound can get good contact with the skin.

Pre-breeding screening requires a more specialist approach as the cysts are likely to be very tiny and hard to identify. The scan must be done by a specialist ultrasonographer using a very high definition machine. Cats must be 10 months old before they can be given a certificate to say that they do not have PKD, because the cysts may be too small to detect before this time.

To qualify for entry on the AD-PKD Negative Register the cat must be scanned by an approved ultrasonographer and must have an identification microchip which can be read at the time of scanning so that its identity can be checked.

For breeding cats the ultrasound test for PKD must be done by a specialist ultrasonographer (so that you can be sure that the result is accurate). If you would like your negative cats to be included on the AD-PKD Negative Register your vet will be able to refer you to an accredited specialist.

If you are not planning to breed from your cat, your own veterinarian may be able to scan your cat and tell you whether or not your cat has large kidney cysts.

Reputable breeders of Persian and Exotic shorthaired cats will have all their breeding cats tested for PKD. If both parents are free of disease the offspring will all be unaffected. Occasionally a breeder may need to have a litter of kittens from an affected cat, and in this case it is predicted that a proportion of the kittens may be unaffected. The kittens can therefore be gene tested to identify which of them have the disease, and which have not.

International Cat Care runs an AD-PKD Negative Register listing cats that have been verifiably tested to AD-PKD and have been found to be negative.

International Cat Care (formerly the Feline Advisory Bureau – FAB) has all the up to date information about the disease and the AD-PKD Negative Register. For further information contact:

International Cat Care
High Street
Tisbury
Wiltshire
SP3 6LD
United Kingdom

Tel: 01747 871 872
Fax: 01747 871 873
Email: info@icatcare.org
Web: icatcare.org