This page
explains more about the various functions of the kidneys.
It is
because the kidneys have so many functions that there are so many
possible symptoms of CKD. Which ones you might see depends upon which
functions are affected.
This page
also explains why CKD is so common in cats.
It
discusses why CKD cannot normally be detected until two thirds of
function has already been lost.
Main Functions of
the Kidneys
The kidneys have five main functions:
the regulation of fluid levels in the body;
the regulation, including filtering and disposal,
of waste products in the body;
the regulation of electrolytes (salts in the body's
cells which are necessary for
survival) in the body;
stimulation of red blood cell production; and
production of renin, which controls blood pressure.
In cats with
CKD,
as the kidneys become more and more damaged and their ability to function declines, an imbalance can arise in any or all of
these areas. So, for example, a cat whose kidneys struggle with the
production of red blood cells will develop
anaemia.
Why CKD Occurs
Most cats
develop CKD
as a result of aging. Studies indicate that around 10% of cats
over the age of ten will develop CKD. Older cats are at even greater risk: as many as 30% of cats over the
age of 15
have the disease. Therefore, if you have a cat aged 15 or over, s/he has a
one in three chance of developing CKD.
Younger cats may also develop CKD but it is less likely. If they are very
young (less than two years old), this may be because of a congenital
problem. Other possible causes include kidney infections, blockages or
exposure to toxins.
Dr
Katherine James mentions that up to 30% of cats aged over 15
develop CKD.
Clinical benefit of calcitriol in feline chronic
renal failure (2005) is a report
by the Morris Feline Foundation on a study by Dr David Polzin into the use
of Calcitriol in cats with CRF. Dr Polzin mentions that 10% of cats over
the age of 10 and 30% of cats over the age of 15 develop CRF.
Management of feline chronic renal failure
(1998) Brown SA Waltham Focus8 pp27-31 mentions that up to
a third of geriatric cats may have CKD, and also discusses the disorders
that may cause renal disease, but does mention that for many cats, the
cause can not be found.
The Cat Doctor
mentions that CKD occurs twice as often in Siamese, Maine Coon,
Abyssinian, Russian Blue and Burmese cats.
The
Causes of CKD page explains more about the various possible
causes, but in most cases the treatment will be the same whatever the cause.
The Role of Nephrons
The main work of the kidneys is performed by units
called nephrons, which filter the blood flowing into the kidneys. The measure of the nephrons’ function is called
glomerular
filtration rate (GFR).
Khan Academy has a clear video showing
how the nephrons work.
Why CKD
Cannot Normally Be Detected at an Early Stage
A cat’s kidneys contain around 170,000 - 190,000
nephrons. This is actually many more nephrons than
are needed for normal function; plus nephrons can increase their individual
function to some extent when other nephrons die. This is why people can
donate a kidney and still manage perfectly well with one kidney. In the
case of a kidney transplant, if you remove one kidney from the
donor, the donor's
GFR (glomerular
filtration rate, a measure of kidney function) will
immediately fall to half of what it was, but will then gradually improve
as the remaining nephrons increase their function to compensate for the
loss of one kidney. Eventually the nephrons in the remaining kidney will reach almost the same level of function as two kidneys.
It works in a similar way in a cat with kidney disease,
i.e. as
damaged nephrons die (they are often described as "scar
tissue"), other nephrons take over their work. Eventually, however,
all the remaining nephrons will be working fulltime (i.e. there will be no
"renal reserve" left). It is at this point, when around 66-75%
of function has gone, that you will probably start to see symptoms in your
cat, as the remaining nephrons start finding it harder to cope with the
workload.
This is also why it is actually normal for CKD not to be diagnosed until
at least 66% of function has been lost.
So please do
not feel guilty for not noticing sooner - there was probably nothing for
you to notice, plus cats are very good at hiding signs of illness. CKD
is not normally painful, so this makes it easier for the cat to hide what
is happening. There
are a number of possible methods of
Early
Detection, but some of these are quite specialised, and most people
wouldn't know about them; in fact, not all vets are familiar with all of
them.
Don't waste your energy beating yourself up. What you need
to focus on is the fact that cats with CKD can often manage quite well on limited kidney function -
for some cats, things only
become critical when they have lost as much as 90% of function, and there
are some cats who cope astonishingly well with even less function. So the
goal is not to worry about the function that has already been lost, but
to try to retain the remaining function for as long as possible, and keep
your cat feeling as well as possible. This site aims to help you with both
goals.
People and pets: common diseases -
kidney disease is a video from
University of California at Davis which provides an overview of what happens
in CKD and shows a dog receiving dialysis. It also features a human CKD
patient talking about how CKD feels.
Kidney Disease is a podcast by Dr
Harriet Syme from the Royal Veterinary College which you can download.
Scroll down to RVC10.
TREATING YOUR CAT WITHOUT VETERINARY ADVICE CAN BE
EXTREMELY DANGEROUS.
I have
tried very hard to ensure that the information provided in this website is
accurate, but I am NOT a vet, just an ordinary person who has lived
through CKD with three cats. This website is for educational purposes
only, and is not intended to be used to diagnose or treat any cat. Before
trying any of the treatments described herein, you MUST consult a
qualified veterinarian and obtain professional advice on the correct
regimen for your cat and his or her particular requirements; and you
should only use any treatments described here with the full knowledge and
approval of your vet. No responsibility can be accepted.
If your cat
appears to be in pain or distress, do not waste time on the internet,
contact your vet immediately.
This site was
created using Microsoft software, and therefore it is best viewed in
Internet Explorer. I know it doesn't always display too well in other
browsers, but I'm not an IT expert so I'm afraid I don't know how to
change that. I would love it to display perfectly everywhere, but my focus
is on making the information available. When I get time, I'll try to
improve how it displays in other browsers.
You may print
out one copy of each section of this site for your own information and/or
one copy to give to your vet, but this site may not otherwise be
reproduced or reprinted, on the internet or elsewhere, without the
permission of the site owner, who can be contacted via the
Contact Me
page.
This site is a labour of love, from which I do not make
a penny. Please do not steal from me by taking credit for my work.
If you wish to
link to this site, please feel free to do so. Please make it clear that
this is a link and not your own work. I would appreciate being informed of
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