Feline Polycystic Kidney Disease

I'll keep this straightforward and as direct as possible as feline polycystic kidney disease is probably one of the best known and widely documented cat diseases. Lets analyse the language:

• Feline = cat
• Poly = meaning more than one or many (Wikipedia)
• Cystic = Having or containing cysts or a cyst (the Free Dictionary)
• Kidney = Either one of a pair of organs that function to maintain proper water and electrolyte balance. They also regulate acid-base concentration and filter metabolic waste from the blood, which are then excreted as urine. (Free Dictionary definition, modified)
• Disease = an abnormal condition of an organism that impairs bodily functions, associated with specific symptoms and signs (Wikipedia,verbatim - this is allowed).

So, we can see that cysts form in the kidneys causing the kidneys to malfunction resulting in the cat becoming ill. Here is some detail. It is an inherited disease. It is found in these cat breeds primarily (Persians and derviates particularly) and in fact all cats to varying levels:

• Persian (very high incidence - reported at 38% in the USA and 49% in the UK (src: http://www.bristol.ac.uk). This may be changing due to better breeding practices. I am not sure as to what date these figures relate to - see Persian cat health problems
  
• Himalayans (a long haired Persian either in Ultra type or traditional)
  
• Exotic Shorthair (a shorthaired Ultra type Persian)
  
• Selkirk Rex
• Maine Coon - and see Maine Coon cat health

As mentioned the disease is inherited. It is caused by a defective autosomal-dominant gene. Autosomal dominant polycystic kidney disease (AD-PKD) is the most common genetic disease in cats (src: http://www.bristol.ac.uk). The cysts can normally be detected using ultrasonography. In 2004, the University of California Davis developed a DNA test for PKD. Accordingly, the disease is now detected by a genetic test from a swab taken from the cheek epithelial cells or from a blood sample. This saves a visit to the vet provided the sample is taken properly.

Because the gene has been identified, over time it should be possible to eradicate the genetic mutation from the breeding lines through selective breeding. I have no data on the current success rates. I am surprised in one way and not in another that these figures are not published widely. Is the incidence of feline polycystic kidney disease in, say, Persian cats on the decline because it should be and if not why not? Apparently positive tests for PKD have been found in virtually all the major lines of Persians, hence the very high incidence of feline polycystic kidney disease in Persians.

Symptoms

What are the symptoms? This is the kind of thing people who live with companion cats want to know, because it will inform them of the disease. It is a "late onset" disease showing up later in the life of the cat, typically at 7 years of age (source: http://www.felinepkd.com/). However, one breeder says she lost cats to feline polycystic kidney disease as young as 18 months of age and up to the age of 14. Obviously kidney function is impaired and they ultimately fail. The symptoms of this disease are then the symptoms of kidney malfunction (i.e. when the presence of the cysts reach a stage when they cause renal failure - when 2/3rds of kidney function is lost - src: Susan Little DVM, DABVP (Feline)), which are:

• depression
• lack of appetite
• excessive thirst
• excessive urination
• weight loss
• vomiting
  

Kidney failure (total loss of function) is apparently certain when the cysts grow and cause ill health. There is cure for feline polycystic kidney disease.

What is Happening?

The kidney's enlarge due to multiple fluid filled cysts. "[the]cysts accumulate fluid, they enlarge, separate entirely from the nephron, compress the neighboring renal parenchyma, and progressively compromise renal function." (Wikpedia verbatim).

• Nephron = the basic structural and functional unit of the kidney. It eliminates wastes from the body and regulates blood volume and blood pressure. It also controls the levels of electrolytes and metabolites, and finally regulates blood pH. (src: Wikipedia modified)
• Renal parenchyma = the functional tissue of the kidney, which includes the nephrons (src: the Free Dictionary)

Click on the following link if you would like to read about Feline Kidney Disease generally. Clearly this short post is to provide us with sufficient knowledge to take immediate steps to see a veterinarian as soon as the symptoms become apparent. As mentioned, the symptoms are those of kidney failure or the kidneys failing. The underlying cause needs to be identified and it may not be feline polycystic kidney disease.



From Feline Polycystic Kidney Disease to Cat Health Problems

Photo: A Vet's cat - by fotobydave and published: