This test
is the least invasive, because initially it does not require that you take
your cat to the vet.
If you
suspect that your cat has gastro-intestinal bleeding (which could be the
case if your cat's
BUN:creatinine ratio is high,
PCV or HCT is falling and
albumin and/or the
MCV are low), you should take a
stool sample to your vet for testing and ask for an occult blood test.
You
can also buy the
EZ Detect test from pharmacies, which
tests for blood in the stool or urine (this is a human test but can also
be used for cats).
I did this
test when Ollie was anaemic. My vet had never been asked to do this test
before, but Ollie's test was positive.
Do not give
iron supplements for a couple of days before obtaining a sample for
testing. Ideally you should also feed no red meat products
beforehand, because red meat may give a false positive. I was reluctant to
restrict Ollie's diet because he was already anaemic and not eating too
well, but Ollie seemed to do well enough on chicken-based foods. Do check
what you are feeding though, many commercial foods contain more than one
meat source.
Veterinary Partner has some helpful
information on gastro-intestinal bleeding.
Both tested kits are
clinically useful for occult blood in cat feces; however, the diet fed
prior to testing must be taken into consideration, and dietary
restrictions are advisable before testing."
The first thing
your vet will do is usually a physical examination of the kidneys by
palpating (feeling and moving) them through the skin. This will tell your
vet whether the kidneys feel small or large (renomegaly)
and he/she may also be able to feel scar tissue, although kidney palpation
alone is not sufficient for a diagnosis.
Most CKD cats,
though by no means all, have small, scarred kidneys.
Many cats with
CKD have dental problems, which in some cases may even have contributed to
the development of CKD. It is therefore important for your vet to keep a
close eye on your cat's mouth and to treat any dental disease, and also to
look for mouth ulcers. Most vets will examine your cat's mouth routinely
at visits, but many dental problems are invisible to the naked eye.
This allows the
vet to examine the kidneys to check their size and to look for certain
abnormalities. Some vets perform ultrasounds routinely, but they are unlikely to be worthwhile if kidneys are small, though
are worth considering if kidneys are larger than expected,
or if the vet thinks kidney stones might be present..
Ultrasound can
also be helpful in diagnosing the existence of a kidney infection
(pyelonephritis). In these cases, the renal pelvis may be dilated (this is
known as pyelectasis), which would be visible on ultrasound. This dilation
may also occur when kidney stones are present. Ultrasound may also be
helpful in diagnosing urinary tract infections, but only if the bladder is
full. In all cases you need an experienced operator.
Where a type of
kidney disease called
Polycystic
Kidney Disease
(PKD) is suspected, an ultrasound can give you some idea how advanced the
condition is.
Ultrasounds are
not invasive and can usually be done without anaesthesia or even sedation,
so there is no need to fast the cat beforehand. The cat may need to
be shaved at the examination site (although my extremely fluffy Chinchilla
Persian had a cardiac ultrasound without being shaved). Cold gel has to be
applied to the body to allow the equipment to work properly, which may be
a little uncomfortable when first applied (ask if you can warm it a little
in your hands first), but all my cats who have had
ultrasounds coped just fine.
Long Beach Animal Hospital has information on ultrasounds
(note: the needle shown is not used during ultrasounds of hearts or
kidneys!; that is for a stomach biopsy, performed under anaesthesia).
Pet Place explains more about abdominal
ultrasounds (no need to register to read the article, just click on Close
at the bottom of the irritating pop-up).
Renal imaging in cats (2008) Seyrek-Intas
D & Kramer M Veterinary Focus18(2) pp23-30 discusses
ultrasounds.
X-rays can be
used to look at the kidneys and to check for stones, but in most cases
palpation and, if necessary, the use of ultrasound make the use of x-rays
unnecessary.
X-rays may
require the cat to be sedated. Some members of
Tanya's CRF Support Group have been allowed to
don lead aprons and hold their cats still for the x-ray instead, but not
every vet permits this.
An IVP is a special type of X-ray which uses a contrast agent to clearly
show the urinary tract. IVPs may be used when tumours or blockages are
suspected. However, the dyes used as a contrast agent may be toxic to the
kidneys, particularly if there is a blockage. The dyes are also excreted
by the kidneys, which is a risk for cats with advanced CKD. These risks must be borne
in
mind when deciding whether to have this procedure.
This is a helpful way of evaluating kidney function and does not
require anaesthesia in most cases. However, it is only available at a
small number of centres, so is normally only used to
assess kidney function prior to removing a kidney because of a tumour or
prior to a nephrectomy (cutting into the kidney, e.g. to remove kidney
stones). It is unlikely to be of any benefit for the typical CKD cat with
small, scared kidneys.
This may be
used in cases where cancer is suspected. Since it requires an anaesthetic,
it should only be done where absolutely necessary. For general
CKD cases,
it is unlikely that a biopsy will be of sufficient value to justify the
risks associated with it, but discuss this in more detail with your vet -
there may be a valid reason in your cat's case.
Most CKD cats have small, scarred kidneys. However this is not
always the case. Cats with a disease called
Polycystic
Kidney Disease (PKD) usually have large, swollen kidneys. Cats with
renal lymphoma,
a form of cancer, may also have large kidneys, as may cats with
perinephric pseudocysts. Another condition called hydronephrosis may
cause enlargement of the kidneys with urine because of obstruction of the
ureter, which prevents urine from passing through. Cats with
acute kidney
injury may have enlarged kidneys.
Occasionally a cat will have one small kidney and one large kidney, a
condition known with startling originality as "big kidney little kidney
syndrome". This is commonly caused by
stones or obstructions.
