Feline polycystic kidney disease

Symptoms an owner can spot at home

• Drinking noticeably more and producing larger clumps in the litter box
• Gradual weight loss over months, often with a duller coat
• Reduced appetite, and increasing fussiness about food
• Vomiting, particularly in the mornings
• Lethargy and less grooming
• In some cats, no signs at all until routine bloodwork picks it up

When to see a vet

• Any cat of an at-risk breed reaching middle age without a kidney screen, book a routine appointment rather than waiting for signs
• A sudden increase in thirst or urination, which warrants bloodwork within days rather than weeks
• Not eating for 48 hours, which risks hepatic lipidosis on top of the kidney disease
• Vomiting more than occasionally, weakness, or a strong ammonia smell on the breath
• Sudden blindness or a dilated, unresponsive pupil, which can indicate hypertension secondary to kidney disease and is an emergency

What it is

Cats with polycystic kidney disease are born with cysts already in the kidneys. The cysts are microscopic at first and enlarge slowly over years, replacing functional tissue. Kidneys carry a large functional reserve, so nothing is visible from outside until a substantial proportion of that reserve is gone, which is typically somewhere between three and ten years of age.

In Persians and closely related breeds, the disease is caused by a single dominant mutation in the PKD1 gene. Dominant means one copy is enough to be affected, which is why it cannot be bred around by pairing carriers carefully, and why removing affected cats from a breeding programme is the only responsible approach.

How vets diagnose it

• DNA test from a cheek swab, valid at any age including in young kittens. This is the definitive test in the affected breeds.
• Abdominal ultrasound, which reliably detects cysts from around ten months of age and shows how extensive they are.
• Routine blood and urine testing, which detects the resulting kidney disease rather than the cysts, and only once enough function is lost.
• Blood pressure measurement, since hypertension frequently accompanies kidney disease and damages the eyes and brain.

The distinction matters when buying. A breeder saying the line is healthy is offering an opinion; a PKD1 result for both parents is evidence. Ask for the paperwork.

Managing a cat who has it

No treatment removes cysts or halts their growth. Management is the management of chronic kidney disease, with the advantage that you can start monitoring years before problems appear. That is genuinely useful, because the dietary interventions that slow CKD progression work best when introduced early, while the cat still has a good appetite.

• Twice-yearly bloodwork and urine specific gravity from middle age, rather than waiting for symptoms.
• A phosphorus-restricted therapeutic renal diet, introduced when your vet's staging supports it and transitioned over one to two weeks.
• Water intake matters. Wet food does most of the work; multiple water stations and a fountain help cats who prefer moving water.
• Regular blood pressure checks and weight monitoring at every visit.
• Never crash-diet an overweight cat with kidney disease. Weight loss has to be gradual and supervised.