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What is
polycystic kidney disease?
Autosomal Polycystic
Kidney Disease (PKD) is a progressive, inherited condition which
causes multiple fluid filled cysts on the kidneys of Persians/Exotic cats
& breeds with Persians/Exotics in their lines.
Cysts are
present from birth, but start out small, slowly increasing in
size. Cysts can range from very small to several centimetres in
diameter. The increasing size of the cysts damage the
normal kidney tissue, eventually causing kidney failure.
The number of
cysts & the speed & size in which they grow varies from
cat to cat. The average age of kidney failure in cats with PKD
is 7 years, but some cats will suffer from kidney failure at an
earlier age & some cats much later, and in fact succumb to
something other than PKD.
How is PKD
inherited?
Genetic studies
in cats have shown that PKD in cats is autosomal (non sex linked
gene) dominant. This means only one parent needs the gene to
pass it onto the offspring. There is a 50% chance of a cat
inheriting PKD if a parent has it. If a cat is genetically free
of PKD it is not possible to pass it onto offspring.
What are the
signs of PKD in cats?
How is it
diagnosed?
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Ultrasound:
Ultrasound diagnosis is 98% accurate after approximately 10
months of age. Ultrasound should be performed by a
veterinarian skilled in the use of ultrasound.
-
Genetic
Test: A swab from inside the cheeks (buccal swab) is
provided to a specialised laboratory for testing. This test
is 100% accurate.
How is it
treated?
There is no way
to slow down the growth of the cysts & they can't be
removed. As the kidneys begin to fail, they lose their ability
to filter out toxins. To understand the treatment it is
necessary to give a brief summary of how the kidney's work;
-
Kidneys help
control blood pressure by releasing an enzyme called renin.
When blood pressure drops and kidneys don’t receive enough
blood, renin is released; causing blood vessels to contract
(tighten). When blood vessels contract, blood pressure goes
up.
-
Kidneys
filter waste products & excess water from the blood. The
cleaned blood stays in the body & the waste products
leave the body in urine.
-
Stimulation
of red blood cell production.
-
They help
maintain the proper balance of acid and minerals, including
sodium, calcium, potassium and magnesium, in the blood.
Therefore
helping reduce the level of toxins in the cat is important.
Treatment is based on that of a cat with chronic renal failure
& may include:
-
Administration
of fluids subcutaneously to treat dehydration.
-
Prescription
diet: Such a prescription diet contains a lower percentage
of protein and less phosphorus than normal cat food. Cats
need protein every day for growth, building muscles and
repairing tissue. After the body uses the protein in the
foods, a waste product called urea is made. Cats with kidney
failure are not able to get rid of this urea normally.
Damaged kidneys may not be able to remove phosphorus from
the blood. This causes the level of phosphorus in the blood
to become too high. A high blood phosphorus level may cause
the cat to lose calcium from their bones.
-
Phosphorus
binders may be
given. These come in tablet or capsule form.
-
High blood
pressure (hypertension): Medication may be prescribed if
your cat's blood pressure is too high.
-
Antacids
& anti nausea medication.
-
Erythropoeitine:
The
kidneys produce a hormone, erythropoietin, which instructs
the bone marrow to produce red blood cells. Cats with kidney
failure often have a low red blood cell count. Only the
human form is available & some cats may eventually
recognise this substance as foreign & antibodies will be
created against it.
What is the
likely outcome for a cat with PKD?
It really
varies from cat to cat. How many cysts are present, how large
they grow & how quickly they grow. A cat with only a few
small & slow growing cysts may live to an old age &
eventually die from something unrelated to PKD. Other cats may
have numerous, large & quick growing cysts & die at an
early age.
Is there a
cure?
No, there isn't
a cure for PKD. Breeders are advised to test their cats & if
they are found to have PKD have them desexed.
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