What Is Polycystic Kidney Disease in Cats?
Polycystic kidney disease (PKD) is a hereditary disorder in which numerous fluid-filled cysts develop within the kidney tissue from birth. Over time, these cysts slowly increase in number and size, progressively replacing healthy functional kidney tissue. As the cysts grow, they disrupt the normal architecture of the kidneys, reducing their capacity to filter blood, regulate electrolytes, and concentrate urine — in other words, causing chronic kidney disease (CKD).
PKD in cats is analogous in many ways to autosomal dominant polycystic kidney disease (ADPKD) in humans, and shares the same fundamental genetic mechanism. It is one of the most prevalent hereditary diseases in cats, with historical surveys suggesting that in some Persian populations, over 40 per cent of individuals were affected before widespread testing became routine.
Which Breeds Are Affected?
PKD is most strongly associated with the Persian cat and breeds derived from Persian lines. Breeds at elevated risk include:
- Persian
- British Shorthair (which has a significant amount of Persian ancestry)
- Exotic Shorthair
- Ragdoll
- Scottish Fold
- Birman
- Himalayan (also known as Colourpoint Persian)
The British Shorthair deserves particular mention as PKD is frequently encountered in this breed in the UK, and many owners are unaware of the risk when purchasing a kitten. Any prospective owner of one of these breeds should ask for PKD test certificates as a matter of course.
The Genetic Basis: Autosomal Dominant Inheritance
Feline PKD is caused by a mutation in the PKD1 gene and follows an autosomal dominant pattern of inheritance. This means that a cat needs to inherit only one copy of the mutant gene — from either parent — to develop the disease. A cat carrying the mutation has a 50 per cent chance of passing it to each kitten.
Homozygous inheritance — receiving two copies of the mutant gene — is believed to be lethal in utero, meaning affected cats in the breeding population carry one normal and one mutated copy of the gene (heterozygous). This autosomal dominant pattern is why PKD can spread rapidly through a breeding line if affected cats are not identified and excluded from breeding programmes.
Importantly, there is no carrier state in the traditional sense: if a cat has one copy of the PKD1 mutation, it will develop cysts. The disease is present from birth, even if clinical signs do not emerge until later in life.
The DNA Test
A reliable DNA test for the PKD1 mutation in cats has been available since the early 2000s. The test requires a simple cheek swab or blood sample and can identify whether a cat carries zero, one, or two copies of the mutation. Because homozygous cats do not survive, test results in breeding cats will be either:
- PKD negative (N/N): the cat carries no copies of the mutation and cannot pass it to offspring
- PKD positive (N/PKD1): the cat carries one copy and will develop cysts; 50 per cent of kittens from this cat may be affected depending on the other parent's status
The DNA test is definitive and does not depend on the cat's age or the current state of the kidneys. It can be performed from a young age, making it possible to test kittens before they are homed.
Ultrasound Diagnosis
Renal cysts can be detected by ultrasound examination from approximately ten months of age. In younger kittens, cysts may be too small to be reliably visualised, even when the PKD1 mutation is present, which is why ultrasound is not considered fully reliable for clearance testing in cats under this age.
Ultrasound remains a useful diagnostic tool — particularly for cats of unknown genetic status, for confirming DNA test results, and for monitoring cyst progression over time in affected cats. On ultrasound, PKD kidneys typically appear enlarged with multiple rounded, fluid-filled structures of varying sizes scattered throughout the parenchyma.
In older affected cats, the kidneys may be dramatically enlarged and easily palpable by an experienced vet during a physical examination. At this stage, kidney function is often already significantly compromised.
Breeding Certificate Requirements
Responsible breeding organisations and major cat registries increasingly require PKD-negative DNA test certificates before a Persian, British Shorthair, Exotic Shorthair, or related breed cat can be registered or shown. In the UK, the Governing Council of the Cat Fancy (GCCF) and many breed clubs have established PKD testing requirements or strongly recommend testing as a condition of registration.
When purchasing a kitten of an at-risk breed, buyers should always request documentation of a negative PKD DNA test from an accredited laboratory for both the sire and dam of the litter. A reputable breeder will provide this without hesitation. Absence of such documentation is a significant red flag and should lead buyers to seek a kitten elsewhere.
The impact of mandatory or strongly encouraged testing programmes on PKD prevalence has been striking in countries where they have been implemented. Prevalence rates have fallen dramatically in tested populations, demonstrating that responsible breeding genuinely makes a difference at the population level.
Progression and When Signs Appear
Despite being present from birth, PKD typically does not cause noticeable illness until the cat reaches middle age or beyond — usually between three and ten years of age, though considerable variation exists. The rate at which cysts grow varies between individuals, and some cats live relatively normally into old age before their kidney function becomes clinically compromised.
When the cyst burden becomes significant enough to impair overall kidney function, the cat develops the signs of CKD: increased thirst and urination, weight loss, reduced appetite, vomiting, poor coat condition, and lethargy. At this point, the clinical picture is indistinguishable from CKD caused by any other underlying condition.
Management: CKD Care Applies to PKD Too
There is currently no cure for PKD in cats, and no treatment to stop cyst growth or reverse the underlying genetic defect. Management of PKD therefore follows exactly the same principles as management of CKD from any other cause.
This includes:
- Phosphate restriction and phosphate binders to slow disease progression
- High-quality, moderately protein-restricted prescription renal diet
- Wet food as the dietary foundation to maintain hydration
- Subcutaneous fluid therapy at home as the disease advances
- Anti-nausea medication and appetite stimulants as needed
- Management of hypertension and proteinuria with appropriate medications
- Regular monitoring of kidney function, blood pressure, and quality of life
Cats with PKD who are diagnosed early through routine screening — whether because of a positive DNA test result or the incidental discovery of cysts on ultrasound — can be enrolled in a monitoring programme before signs develop. This allows any deterioration to be caught early and managed proactively, giving the cat the best possible outcome. Regular six-monthly or annual blood and urine checks are recommended for known PKD-positive cats, even before overt kidney disease develops.