Chronic renal failure (CRF) - more
commonly known as kidney failure - is unfortunately all
too common in our feline patients. Throughout life, all
sorts of "wear and tear" can progressively damage
The kidneys have a large "functional
reserve" - in other words, we do not need all of our
kidneys to be in good working order to cope and perform
all the required functions. Indeed, a patient can happily
survive if one kidney needs removing. Thus, cats do not
show any symptoms of kidney disease until at least two thirds
of the kidneys are damaged.
Unfortunately, in CRF, we cannot reverse the
damage that has been done; the best we can hope for is to
try to help the remaining one third (or less!) of working
kidney to cope as best it can, and also try to "stop
the rot" - ie: slow down the rate of ongoing kidney
When "Lucy"'s owners noticed that
she was drinking slightly more than normal, the possibility
of kidney disease was foremost in their minds. Polyuria
and polydipsia (excessive urination and thirst) are amongst
the commonest signs of CRF.
I always tell clients that an increase in
thirst should NEVER be ignored. Weight loss, vomiting, dullness
and - in advanced cases - ulcers in the gastrointestinal
tract and seizures are all symptoms of CRF.
Lucy's owners were vigilant and brought her
in at the first sign of a problem. Blood tests showed that
the levels of certain toxins in her blood (which the kidneys
would usually eliminate from the body) were raised. This
indicated that the kidneys were no longer functioning effectively.
In early cases of CRF, there is much that can be done to
The mainstay of treatment involves feeding
a diet that is low in protein and phosphorous. The toxins
that accumulate in CRF are waste products from protein digestion.
Thus, less protein means less wastes are produced, and the
kidneys have less work to do excreting these wastes. Keeping
the levels of phosphorous low is crucial as it slows down
the advancing kidney disease. Unfortunately, cats love high
protein foods, and some will not take to a low protein/phosphorous
diet. We can still keep phosphorous levels controlled, however,
even without a special diet, by giving drugs that prevent
phosphorous being absorbed in the bowels.
As CRF progresses, the part of the kidneys
which is still working tries to do the job of all the kidney
tissue, so it "over works". This may seem sensible,
but unfortunately, by working so hard, the remnants of normal
kidney wear out even faster. A drug called benazepril is
a recent advancement in the treatment of CRF as it reduces
this "over-working" so that the remaining healthy
kidney tissue lasts for longer.
Other important factors in treating CRF include
monitoring of blood pressure. CRF can actually cause high
blood pressure, and this is a vicious circle because high
blood pressure hastens the kidneys' demise. Thus, cats with
high blood pressure are put onto amlodipine - a human drug
that reduces the pressure.
Finally, regular urine tests to monitor for
urinary infections are important. Cats with CRF are more
prone to water infections. Once again, there is a vicious
circle, because infections add to the kidney disease.
In cats such as Lucy, where problems were
detected early, the measures described may hold her kidney
disease at bay for a long time. In cats where the disease
is more advanced, it is not so simple. Human patients would
receive dialysis and possibly transplants. Until recently,
this was out of the question for feline patients. However,
the Royal College of Veterinary Surgeons (RCVS) has recently
approved theoretical proposals to allow kidney transplants
to be performed in cats.
This has raised huge ethical questions. Unlike
with man, a cat cannot give consent to donate a kidney,
and moral arguments regarding the use of donor cats are
understandably being raised. There is concern that cats
may be bred purely to be used as donors.
One suggestion as a source of donor cats is
rescue centres. An idea has been put forward that an unwanted
or stray cat at a rescue center could be used to donate
one kidney, and the owner of the recipient cat would then
be obliged to give the homeless donor cat a home for life.
This way, both the cat with kidney disease and the homeless
cat would get a positive outcome.
Another concern is that the cat who has donated
a kidney may well develop kidney problems of its own, much
earlier than would otherwise have happened because it has
less "spare" kidney tissue.
Should kidney transplants go ahead, they will
be tightly regulated, and only performed at specialist centers
with the required expertise (ie: you won't be able to steal
a neighbours cat, pinch its kidney and get it implanted
into your own cat at a back street clinic!!!). A transplant
is likely to cost in excess of £8000! As far as I
am aware, there have as yet been no transplants performed,
but it would seem that - approve or not - it is just around
the corner. Watch this space!
Young BVSc CertSAM MRCVS
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