Home > Related Diseases > Polycystic Kidney Disease
Overview
- Polycystic kidney disease, or PKD, is a genetic disease which causes cysts to develop in the kidneys.
- It is most common in Persian cats.
- Eventually, as the cysts grow, the cat may develop CKD.
What is Polycystic Kidney Disease?
Polycystic Kidney Disease, known as PKD, is an autosomal dominant genetic disease of the kidneys which is passed on by one or both parents; siblings may be unaffected. PKD affects around 6% of all cats, but appears to be more common in Persian cats, British Shorthairs and others with Persian ancestry. One of our cats, Harpsie (left), had PKD.
The distinguishing characteristic of PKD is that cysts are present, usually on both kidneys, and as the cat gets older, these cysts often increase in size and multiply. Eventually kidney function may be diminished to the extent that CKD develops.
Some PKD cats may also show cysts in their liver — Harpsie also had these. Polycystic kidney and liver disease in cats (1998) Bosje JT, van den Ingh TSGAM & van der Linde-Sipman JS Veterinary Quarterly 20(4) pp136-139 found that “In 12 of the 18 cats (67%) with multiple rounded cysts in the kidney (PKD) in which the liver was examined, there were also cystic changes of the liver.” It also found that, out of 27 cases in total, “In 5 cases there was severe pancreas fibrosis.”
Cats tend to develop PKD around the age of 5 – 7 years (Harpsie was diagnosed at the age of 7) but seriously affected cats with multiple cysts can fall ill when they are as young as two. Stress or infection can accelerate this disease.
However, CKD is not inevitable – it depends how badly the kidneys are affected, and some PKD cats die from other causes before reaching CKD status. Harpsie lived to 14, so he managed seven years after his PKD diagnosis, and although his cysts were growing, he did not have CKD when he died (he died of cancer).
There is another type of cyst called perinephric pseudocysts (or perirenal pseudocysts) associated with CKD, so if your vet mentions cysts, be sure you know which type is meant.
International Cat Care has a good overview of PKD.
Universities Federation for Animal Welfare has detailed information about PKD.
Cornell University College of Veterinary Medicine explains more about PKD.
Symptoms
PKD is usually asymptomatic, but a PKD cat may exhibit polydipsia (increased thirst), and in some cases the kidneys will feel enlarged (though there are other possible causes for this, see renomegaly).
Many PKD cats show a slight heart murmur and slightly swollen kidneys before CKD develops, and male PKD cats are often susceptible to FLUTD (feline lower urinary tract disorder), which Harpsie also had.
Harpsie also had frequent kidney infections: these are relatively common in PKD cats because the bacteria can burrow deep into the cysts.
If the disease progresses so far that CKD results, then the usual CKD symptoms will be present, and the usual treatments can be used as appropriate.
PKD itself is generally considered not to be a painful disease. Unfortunately, this may not apply to cats who progress to severe end stage PKD: these cats may suffer pain from the cysts growing rapidly and occasionally rupturing. Sadly, nothing can be done to prevent this, but you do need to watch for it occurring in a PKD cat so you can discuss your options (such as painkillers) with your vet. Infected cysts may also cause pain, and painkillers should always be considered during treatment for the infection.
Diagnosis
Gene Testing
The University of California at Davis identified the gene mutation that causes PKD in 2004. Feline polycystic kidney disease mutation identified in PKD1 (2004) Lyons LA, Biller DS, Erdman CA, Lipinski MJ, Young AE, Roe BA, Qin B & Grahn RA Journal of the American Society of Nephrology 15(10) pp2548-55 reports on the discovery.
Gene Testing: USA
The University of California at Davis offers genetic testing at a cost of US$40 per cat. The test can be run as soon as a kitten is 8-10 weeks old and is almost 100% accurate. You can obtain the sample yourself, it is obtained by non-invasive means so your vet does not need to be involved. You will be sent the results via e-mail.
DDC Veterinary in Ohio offers a similar test for US$48.
Gene Testing: Europe
The University of Bristol Langford Veterinary Services can perform testing for £36.60. It will also perform the test for people outside the EU if they provide additional information.
Ultrasound
The only other way to diagnose PKD properly is via an ultrasound of the kidneys. An ultrasound, as explained by Evaluation of the repeatability of ultrasound scanning for detection of feline polycystic kidney disease (2010) Wills SJ, Barr FJ, Bradley KJ, Helps CR, Cannon MJ & Gruffydd-Jones TJ Journal of Feline Medicine & Surgery 11 p993, is the only way to diagnose non-autosomal dominant forms of PKD.
Ultrasounds also allow you to see how many cysts are present and how severe the cysts are. Age-based ultrasonographic criteria for diagnosis of autosomal dominant polycystic kidney disease in Persian cats (2018) Guerra JM, Freitas MF, Daniel AG, Pellegrino A, Cardoso NC, Castro I, Onuchic LF & Cogliati B Journal of Feline Medicine and Surgery 21(2) pp156-164 examined whether ultrasound could be used to consistently diagnose PKD in Persian cats and found that “the presence of at least one renal cyst was sufficient to establish a diagnosis of ADPKD in animals up to 15 months of age. Two or more cysts were required for diagnosis in cats aged 16-32 months, and at least three cysts warranted diagnosis of ADPKD in animals aged 33-49 months. Finally, four or more cysts led to diagnosis in cats aged 50-66 months.”
Ultrasound is a reasonably accurate method of diagnosis if it is undertaken by a person skilled in sonography, and ideally with experience of PKD kidneys. Repeated scans may need to be taken if the cat is very young as the cysts may not be visible at that time: it is often hard to detect PKD in cats less than nine months old.
Cysts are rare in cats but not all cysts are necessarily PKD; research is still being done in this area.
If you have a Persian cat suspected of having hypertrophic cardiomyopathy (HCM), a type of heart problem, and are planning to have the heart examined by ultrasound, I would recommend having the cat’s kidneys examined by ultrasound at the same time in order to rule out PKD. This was how we discovered that Harpsie has PKD — the cardiologist checked his kidneys when he checked his heart.
Treatments
PKD is incurable and sadly, there are very few treatments available other than the standard treatments for CKD. Try to ensure that your cat leads a stress free life, free of infection and toxicity. A soy protein diet may possibly help.
In principle the cysts could be drained. However, Cornell University College of Veterinary Medicine says “It is conceivable, according to Dr. Goldstein, that cysts within the kidney could be drained with a needle in a procedure guided by ultrasound imaging. “But there usually are so many cysts,” he notes, “that this is not a viable option. And even if you did drain all of them, they would fill up with fluid again.””
In theory, it might also be possible to remove the cysts surgically, though the same issues apply as with draining them. Having said that, one member of Tanya’s CKD Support Group did have her PKD cat’s cysts surgically removed and they did not grow back for four years.
We found that our PKD cat was very prone to kidney infections. Around 30-50% of human PKD patients will develop a urinary tract infection, and Renal infections in autosomal dominant polycystic kidney disease (1987) Sklar AH, Caruana RJ, Lammers JE & Strauser GD American Journal of Kidney Disease 10(2) pp81-8 reports that these can be difficult to treat, especially if the infection is in the cysts themselves.
Polycystic kidney disease in four British shorthair cats with successful treatment of bacterial cyst infection (2015) Nivy R, Lyons LA, Aroch I & Segev G Journal of Small Animal Practice 56(9) pp585-9 states that infected renal cysts have not previously been reported in cats but in this study a cat with an infected cyst was successfully treated.
Potassium citrate/citric acid intake improves renal function in rats with polycystic kidney disease (1998) Tanner GA American Society of Nephrology 9 pp1242-48 indicated that potassium citrate may help PKD rats; it is not known if this also applies to cats, but potassium citrate is an ingredient in Royal Canin’s Persian cat food. Do not supplement potassium without your vet’s knowledge and approval.
Selective ablation of symptomatic dominant renal cysts using 99% ethanol in adult polycystic kidney disease (2006) Singh I & Mehrotra G Urology 68(3) pp482-7 was a study in India that found that injecting alcohol into cysts helped humans patients whose primary symptom was pain from dominant cysts. I am not aware of any evidence that this would help cats, though in 2013 I did hear from one person whose vet was considering this treatment for her cat.
If the PKD develops into CKD, then the usual CKD treatments can be used as appropriate, as described elsewhere in this site.
Research
There is limited research into the treatment of PKD in cats, since the current focus is on eradicating it from breeding lines, which in the longer term is of course the best approach. The University of Bristol Langford Veterinary Services explains more about genetic testing and has a graph showing how this is gradually helping to eradicate the disease.
The following links therefore contain information about research into certain drugs which appear to slow the progression of the disease in humans or mice only. I am not aware that anyone has used these treatments in cats.
Management of ADPKD in 2016 and beyond (2016) Perrone RD National Kidney Foundation’s 2016 Spring Clinical Meetings discusses the current position regarding research into PKD in humans.
Vascular endothelial growth factor C for polycystic kidney diseases (2016) Huang JL, Woolf AS, Kolatsi-Joannou M, Baluk P, Sandford RN, Peters DJM, McDonald DM, Price KL, Winyard PJD & Long DA Journal of the American Society of Nephrology 27(1) pp69-77 treated the tiny blood vessels around the cysts in mice with PKD with a growth factor called vascular endothelial growth factor C (VEGFC). The study found that the blood vessels normalised and states “these effects were associated with significant reductions in cystic disease, BUN and serum creatinine levels.”
Sirolimus therapy to halt the progression of ADPKD (2010) Perico N, Antiga L, Caroli A, Ruggenenti P, Fasolini G, Cafaro M, Ondei P, Rubis N, Diadei O, Gherardi G, Prandini S, Panozo A, Bravo RF, Carminati S, De Leon FR, Gaspari F, Cortinovis M, Motterlini N, Ene-Iordache B, Remuzzi A, Remuzzi G Journal of the American Society of Nephrology 21(6) pp1031-40 looked at the use of sirolimus in human patients. Sirolimus (rapamycin) is an immunosuppressant drug used to prevent rejection in organ transplants, particularly kidney transplants. The study found that sirolimus “halted cyst growth” in the human patients in the study.
Low-dose rapamycin (sirolimus) effects in autosomal dominant polycystic kidney disease: an open-label randomized controlled pilot study (2014) Braun WE, Schold JD, Stephany BR, Spirko RA & Herts BR Clinical Journal of the American Society of Nephrology 9(5) pp881-8 is a later study into the use of sirolimus which concluded “Patients with ADPKD receiving LD rapamycin demonstrated a significant increase in iGFR compared with those receiving standard care, without a significant effect on TKV after 12 months.”
Autosomal dominant polycystic kidney disease: pathophysiology and treatment (2007) Rapoport J Quarterly Journal of Medicine 100 pp1-9 reports on a number of possible treatments for humans with PKD.
Effective treatment of an orthologous model of autosomal dominant polycystic kidney disease (2004) Torres VE, Wang X, Qian Q, Somlo S, Harris PC, Gattone VH 2nd Natural Medicine 10(4) pp363-4 reports on the use of OPC-31260 in mice.
Effectiveness of vasopressin V2 receptor antagonists OPC-31260 and OPC-41061 on polycystic kidney disease development in the PCK rat (2005) Wang X, Gattone V 2nd, Harris PC, Torres VE Journal of the American Society of Nephrology 16(4) pp846-51 reports on research on rats into OPC-31260 and another drug called OPC-41061 which may slow the progression of PKD.
This page last updated: 08 June 2022
Links on this page last checked: 30 April 2020