This is usually one of the first questions people ask themselves after
diagnosis.
This page attempts to help you understand a bit more about
what the test results mean, and why they do not
tell the whole story.
It also explains why
it is not as bad as it sounds when your vet says your cat has lost a
certain percentage of his/her kidney function.
How
Bad Are My Cat's Results?
There are a number of ways in which the vet can
determine how advanced your cat's case is. Most vets will start with
bloodwork, and many will also analyse your cat's urine (urinalysis).
Many vets now take the test results and categorise them
according to the system proposed by the
International Renal Interest
Society. This divides CKD
into four stages based on blood and urine test results;
so if your vet tells you, for example, that your cat is in Stage 2, s/he
is probably referring to the IRIS staging system. There is more
information on this below.
Remember, your cat's test results are only part of the
story. There are other factors at play, including how your cat is
acting, how proactive your vet is, whether there is an infection etc. For
this reason, we have a mantra on
Tanya's CRF Support Group:
treat the cat, not the numbers.
Bloodwork tells vets quite a lot about how a cat's
kidneys are functioning.
BUN (urea) and
creatinine
are the two main measures of kidney function in bloodwork. Here is the
IRIS staging system, with my estimate of the likely percentage of function
lost:
Stage of Disease
Blood Values:
US
Measurements (mg/dl)
Blood Values:
International Measurements
(µmol/L)
Approx.
Level of Kidney Function Lost
Stage 1
Creatinine below 1.6
Creatinine below 140
0 -
65%
Stage 2
Creatinine
between
1.6 and 2.8
Creatinine between
140
and 249
66 -
75%
Stage 3
Creatinine
between
2.9 and 5.0
Creatinine
between
250 and 439
76 -
90%
Stage 4
Creatinine over 5.0
Creatinine over 440
Over 90%
*It is normal not to be able to detect
CKD until at least 66% of function has been lost, because before that there
are usually no symptoms, see
below.
Therefore for cats in Stage 1, bloodwork values are usually within
the normal range, and kidney problems would
only be suspected if an
anatomical or functional abnormality had been detected.
In all cases, two readings in a stable cat (who is not
dehydrated - this can make the numbers look a lot higher than they really
are), ideally
after fasting (though that is not always the best choice for a CKD cat), are required
before making a firm diagnosis of CKD. In practice, most vets will make
the diagnosis based on bloodwork taken once during your initial visit.
Urine Specific Gravity (USG)
Because of their desert heritage, healthy cats have concentrated
urine. The normal range is 1.008 to 1.060 but a cat with a
more dilute USG,
below 1.040, is generally considered to have a problem of some kind.
A CKD cat will probably have a USG
between 1.008 and 1.012.
Once a cat is receiving regular fluid therapy, this test can be rather
unreliable; but it may be helpful when blood tests first indicate a
possible problem, particularly if your cat appears to be in early stage.
There is more information about USG on the
Urinalysis
page.
Healthy
cats only have tiny amounts of protein in their urine because their
kidneys do not allow the protein to leak through. In CKD cats, this
mechanism can be faulty and excess levels of protein in the urine, known
as proteinuria but sometimes referred to as
microalbuminuria, may occur.
The usual way to determine if a cat has proteinuria is via
the urine protein:creatinine ratio (UPC):
Urine Protein: Creatinine Ratio
Proteinuria
Status
Below 0.2
Non Proteinuric (NP)
Between 0.2 and 0.4
Borderline Proteinuric (BP)
Over 0.4
Proteinuric (P)
There is a correlation between the severity of the proteinuria and the
prognosis. However, don't panic if your cat's level is over 0.4 because the UPC
ratio is not always accurate - for example,
blood in the urine, infection or
inflammation may give a false positive result.
Hypertension may worsen proteinuria, so getting blood pressure under control may lead to an
improvement in the UPC ratio. Even if your cat's UPC ratio is indeed high, it
may gradually reduce with
treatment.
You may well panic if your vet tells you that your cat has lost
two thirds or more of his/her kidney function. I regularly hear from
people who say things like "my vet told me my cat has lost 75% of kidney function and
it's looking really bad".
Take a deep breath. It is probably not as awful as you fear because it is actually normal for
CKD not to be diagnosed until
a cat has lost at least 66% of kidney function. The
What
Happens in CKD? page has more information on why this is the case.
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 help your cat manage with whatever function remains for as long as possible.
You may also be frightened because your vet says your cat's
kidneys have failed. Fortunately, this may not be as bad as it sounds.
There are a number of different expressions used to
describe chronic kidney disease. It used to be widely known as chronic
renal failure (CRF), and for many years this website was known as Tanya's
Comprehensive Guide to Feline Chronic Renal Failure.
I decided to changed the name in 2011 and use the
expression Chronic Kidney Disease (CKD) instead. This was for two reasons.
Firstly, it is the term most commonly used in the academic literature.
Secondly, I think it more accurately reflects the nature of the disease,
and focuses on the important word, "chronic" rather than on that awful
word, "failure", which tends to scare people, making them feel the end is
nigh.
Chronic means that CKD is an
ongoing disease. This is good news, because it means that in many cases it can be managed.
For this reason, some vets prefer to use the
word "insufficiency" for early stage cases instead.
Whatever expression your vet uses, try to focus on the
chronic aspect of CKD.
This
expression literally means that the cat's kidneys are at the point of
failure and there is no longer anything that can be done. Some vets use it
in this sense, referring to a cat who is rapidly becoming unable
to deal with the CKD, ceasing to respond to treatments and likely to die very
soon. However, other vets use it to mean any cat with numbers in the range of Stage 2
or 3 (see above),
when in fact many cats in these stages can live for a long time.
Try to clarify what your vet means by ESRD, and if he/she merely
means that your cat has high numbers, consider treating the cat; the
numbers may come down with treatment, and even if they don't, your cat
might be able to handle high numbers as Thomas did. Even if your vet
thinks death is imminent, it may be worth treating your cat regardless to
see how he or she responds; cats are real fighters and can often pull
through.
Obviously though, you don't want your cat to be in pain when it
is a hopeless situation. It is not always easy to tell when a CKD cat has
come to the end of the road -
The
Final Hours contains details of the symptoms you
are likely to see towards the end, and discusses making the painful
decision to let go.
If Your Vet Has Recommended
Euthanasia
When vets tell people there is no hope for their cat, it is usually based
on test results as outlined above, particularly blood tests which show high kidney values.
However, I have heard of vets who tell people their cat should be put to
sleep without doing any tests at all, based purely on the cat acting sick.
I don't think this is appropriate. Your vet may be right, there may be no
hope for your cat, but if you're thinking of making the irrevocable
decision to put your cat to sleep, you need proper, accurate information
on which to base your decision.
Even if you do have some blood test results, the numbers only tell part of
the story.
In
Renal disease (2006), Dr D Polzin states
"Severity of renal dysfunction as determined by serum
creatinine concentration or measurement of GFR provides a less accurate
means of assessing short-term prognosis than does the clinical condition
of the patient. The relationship between magnitude of renal dysfunction
and clinical signs of uremia is often unpredictable. Therefore, short-term
prognosis should not be established on the basis of a single measurement
of the severity of renal function. In addition, a single determination of
renal function is unreliable as an index of the potential for improvement
in renal function." In
The laboratory diagnosis of feline kidney disease
(2008) Heine R Veterinary Focus18(2) pp16-22, Dr Heine
states "cats can sometimes, especially in cases of acute
kidney injury secondary to obstructive
FLUTD,
develop creatinine values of 1600-1800 μmol/L
(20.98-23.6 mg/dL) and yet recover."
I don't know why some vets don't try to fight CKD. Perhaps they think it's
not worth trying because CKD is incurable. Yes, CKD is incurable, but it
can often be managed so your cat feels better. As one member of Tanya's
CRF Support Group said, "vets are about the cure, we are about
the care."
So try not to worry too much about which stage your cat is in, especially
since numbers can be artificially inflated at diagnosis. The stages are
supposed to help the vet roughly work out which treatments are likely to
be needed, not to encourage them to write off cats in the higher
categories. Yes, your cat's chances may be worse if your cat is - and
remains - a high numbers cat; but some cats do well despite high numbers,
so try treating the cat, not the numbers and see what happens.
Therefore, if your vet has told you there is no hope for your cat,
and has recommended euthanasia, I urge you to:
read this page, and also the Is
There Any Hope? page to
explore the various scenarios you may be facing;
ask your vet
about trying some of the
Treatmentsthat are appropriate for any of the symptoms you are
seeing and any imbalances indicated by your cat's test results;
before making
the irrevocable decision to put your cat to sleep.
so you can nip these problems in the bud if they
are present.
In virtually all cases it is worth trying treatments for at least two
weeks.
The International Renal Interest Society has some suggestions on what to watch for and be prepared to
treat at each stage, including what to do if proteinuria or hypertension
are present.
Whatever stage your cat is at, most people find the
treatments only take about 20 minutes out of their day, including the time
needed to give sub-cutaneous fluids.
Here are some tips on what you may
be facing:
Cat in IRIS Stage 1, Stage 2 or the Lower End of Stage
3
If your cat seems to fall into IRIS Stage 1, 2 or the lower
end of Stage 3, it is early stage and with proper care and a little luck
on your side, your cat could live for years.
Most cats in these Stages (creatinine below 3.5-4.0
mg/dl US or 300-350
µmol/L international) will not need subcutaneous fluids and can
easily be managed with just a few treatments tailored to the individual
cat's needs, e.g. treatment for stomach acid to prevent vomiting,
constipation remedies and/or control of elevated phosphorus levels.
In all cases, it is essential that your cat eats!
Cat in Stage 4 or the Upper End of Stage 3
If your cat seems to fall into Stage 4 or the top end
of Stage 3, don't despair. You may not be seeing the true
situation. Bloodwork can appear high for the following reasons:
the cat is severely dehydrated
the cat has an untreated urinary tract infection or a kidney
infection
the cat has untreated hypertension (high blood pressure)
the cat has kidney stones
In such cases, the numbers you are seeing won't be an accurate
representation of true kidney function.
You need to treat your cat, particularly any
dehydration, before you can know the true status of the kidneys.
Even if your cat proves to be at the top of Stage 3 or
in Stage 4 following stabilisation, don't give up hope: some cats do seem
to manage very well on very little kidney function, and it is possible
that your cat might be one such cat. You will probably need to be more
proactive and your cat will usually need more treatments than cats with
lower bloodwork values, but it is certainly worth trying to help.
These cats will usually need the same treatments as
cats in lower stages for whatever problems may be present, e.g. for
stomach acid, high phosphorus levels, constipation etc. In addition, they
will usually need regular fluid therapy in the form of sub-cutaneous
fluids in order to avoid dehydration.
Cats in IRIS Stage 4 will often have anaemia, and will
need treatment for that - untreated severe anaemia can be very dangerous
and can kill a CKD cat before the CKD does. Fortunately, many effective
treatments for anaemia are available, meaning no CKD cat need die of
anaemia. See the
Anaemia page for more information.
Cats in IRIS Stage 4 may have metabolic acidosis, so
ensure your vet checks for that and treats it if it is present.
