Polycystic kidney disease (PKD)

How it progresses

Cats with PKD are born with cysts already present. The cysts are tiny at first and cause no problem, then enlarge over years. Kidneys have substantial reserve capacity, so signs appear only once enough functional tissue has been crowded out, usually somewhere between three and ten years of age.

At that point the presentation is chronic kidney disease and is not distinguishable from CKD caused by anything else: drinking and urinating more, gradual weight loss, reduced appetite, poor coat. The underlying cause changes the prognosis conversation and the breeding decision, not the day-to-day management.

The test is definitive, which is unusual

Most inherited feline disease is a matter of probability. PKD in Persians and related breeds is caused by a single dominant mutation in the PKD1 gene, so one cheek swab gives a clear answer, and because the mutation is dominant a cat with one copy is affected. Ultrasound also detects cysts reliably from around ten months of age.

• Buying a Persian, Exotic, British Shorthair, Scottish Fold or any outcross of those: ask for the parents' PKD1 DNA results in writing.
• Responsible breeding removes affected cats from the programme entirely, because a dominant gene cannot be bred around by pairing carriers carefully.
• Adopting an adult cat of an at-risk breed with unknown history: an abdominal ultrasound is a reasonable one-time investment, and it establishes a baseline either way.

Managing a cat who has it

There is no treatment that removes cysts or stops them growing. Management is CKD management, started earlier because you know it is coming. That is genuinely valuable, since the dietary interventions that slow CKD work best when they begin before the cat feels unwell.

• Twice-yearly bloodwork and urine specific gravity from middle age, rather than waiting for symptoms.
• Water intake matters. Wet food, multiple water stations, and a fountain if the cat prefers moving water.
• A phosphorus-restricted renal diet is introduced on your vet's staging, not pre-emptively.
• Blood pressure checks, because hypertension travels with kidney disease and damages eyes and brain.

Why it matters

PKD is one of the few serious feline diseases you can definitively avoid at the point of purchase. A breeder who tests has nothing to hide and will produce the paperwork without being pushed; one who deflects with reassurances about healthy lines is telling you something. For a cat who already has it, knowing years ahead of symptoms is a real advantage, because it converts a crisis diagnosis into a slow, monitored decline you can plan and budget for.