Urinalysis is the term used to refer to a series of tests run on a urine
sample. These tests can
help to confirm the CKD diagnosis, or may give an early warning. They are also used
to check for imbalances and infections.
Urine samples may be obtained in a number of ways.
Some methods (free catch and non-absorbent litter) can be used at home so
you can then take the sample to your vet for testing. Samples obtained in
this way are sufficient to run most of the tests below, but are not sterile,
so are not suitable for running a culture and sensitivity test (see
below). In this situation, ideally you need to take your cat to your vet
for cystocentesis.
If you do obtain a sample at home, ideally you want to take it to the vet
within four hours.
Feline Good has photos of urine collection
via the Nosorb and cystocentesis methods.
Free Catch
Free catch means that you stick a container under your cat as s/he urinates and catch some urine in
it. I can't imagine my cats tolerating this but some people's cats don't mind,
in which case it is probably the quickest and easiest way.
My Vet Meds sell a similar product (the
Uripet) for
£1.67 each.
Some people use a ladle, which is a good idea because you don't need to
get too close to your cat.
Non-absorbent Litter
and Detecting Litter
Nosorb
litter is made of non-absorbent granules. You put it in the litter tray in place of normal litter, and since
it does not absorb urine, you can scoop up some urine to take to the vet. NoSorb can
be washed and re-used.
Kit 4 Cat
is another type of non-absorbent litter that is apparently very similar to real
(sandlike) litter.
Katkor
is a non-absorbent litter available in a variety of European countries.
My vet sells the Smart Cat Urine Test Kit for £2 a packet.
My cats like a lot of litter, so I use two bags, but some people do only use one bag.
This is a one use only kit.
The Pet
Check Up is a test that
checks for blood in urine, and which may also be used to check for other
issues, such as diabetes.
Zooplus in Europe sells a detectable
litter called Perlinette.
I don't know anybody who has used it yet.
Although these tests can give
you some basic information, e.g. the presence of blood or bacteria, you
should take the sample to your vet for proper analysis. The white blood
cell reading in the urine test itself is often inaccurate.
Cystocentesis
This is the best way to obtain a sterile sample, which is required in order to
run a culture and sensitivity test to check for infections. Cystocentesis
means the removal of urine from the bladder via a fine needle. It
sounds far worse than it is, I've seen this done on my cats and they do not
even flinch. It is safe as long as you have a competent vet, who should use
ultrasound to guide the needle. It is only suitable for a cat who has
urine in the bladder, and is usually not appropriate for a cat who
struggles at the vet's.
Urinary tract infection: how to diagnose and treat
correctly (2003) is a presentation by Claudio Brovida to the
World Small Animal Veterinary Association World Congress 2003, which
explains why cystocentesis is the ideal method of urine collection, but not
always possible.
Pet Place describes how cystocentesis is
performed (no need to register to read the article, just click on Close at the
bottom of the irritating pop-up).
The urine
sample will be used to run a number of different tests, which will provide
your vet with a variety of information about various aspects of your cat's
health. The tests include:
The urine specific gravity (USG) test checks whether the cat is concentrating urine appropriately.
Because of their desert heritage, in normal circumstances healthy cats have concentrated
urine, but CKD cats usually have dilute urine. This test should be run by refractometer - using the dipstick method is
rather unreliable.
The normal range is 1.008 to 1.060,
but a cat with a USG
below 1.040 is generally considered to have a problem of some kind, and
in a cat with normal bloodwork, it may be an early warning sign that CKD
is developing. Most
CKD cats have a much lower USG of between 1.008 and 1.012, which is known as isothenuria.
Prolonging life and kidney function
(2007) a paper presented to the 32nd World Small Animal
Veterinary Association Congress by Dr D Chew,explains more
about this.
Although these
numbers have a decimal place after the 1, vets often say the numbers
verbally in a different way, so for example, a USG of 1.012 would be
referred to as "ten twelve" rather than "one point oh one two."
Cats with
pyelonephritis (kidney infection) may have a low USG.
Cats
with diabetes
or hyperthyroidism
may also have dilute urine. Other possible causes of dilute urine include
liver disease or use of
corticosteroids.
A cat's USG level may also change quite a lot over the cause of the day.
Before diagnosing CKD, therefore, the test should be run more than once
and other causes ruled out.
Once a cat is receiving regular fluid therapy, this
test can be rather unreliable.
This is a measure of particles
dissolved in solution, and measures the concentration of the urine.
It is usually used in conjunction with USG. The approximate normal range
for urine osmolality is
270-320.
Serum (blood) measurement of osmolality gives some indication of
hydration levels - a dehydrated cat will often have high osmolality,
while an
over-hydrated cat will usually have low levels. High levels may also
indicate
azotaemia.
Rn Ceus
is a human nursing site with some information on osmolality.
Proteinuria
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 (though sometimes referred to as microalbuminuria), may occur. The main
proteins which leak through are
albumin
and globulin. The
degree of proteinuria is usually indicated by the number of + signs on the
test result, with more + indicating greater severity, so Protein +++ is
more severe than Protein +.
The
existence of proteinuria
has recently been determined to be extremely important in the early
detection of CKD (see protein:creatinine ratio
below), and in fact forms the basis for a
new
test devised to diagnose kidney disease early in cats.
If your cat
seems to have proteinuria, you should have the test run again in case it
is inaccurate. Blood in the urine, for example, can give a false positive.
Proteinuria can
make weight loss worse, and may also cause other symptoms, such as
swelling in the legs, abdomen or face. See
Symptoms
for more information and
Treatments
for more information on how to handle it.
Pet Place has a non-technical explanation of
proteinuria (no need to register, just click on Close at
the bottom of the irritating pop-up).
The International Renal Interest Society uses
protein in the urine as a risk factor for the development of CKD, and as a
factor in
determining the severity of the CKD:
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)
The UPC ratio is
often higher if the cat has
glomerulonephritis. The reading will
not be reliable if there is infection or inflammation in the
urine.
This is
usually
a sign of a urinary tract infection, or
bladder or kidney stones. However, if your vet obtains a
urine sample from your cat via cystocentesis (a needle into the bladder),
this may sometimes cause blood in the urine.
Other
possible causes include
high blood
pressure. or, occasionally, cancer. Ollie had this symptom towards the
end, and I think it might have been because of cancer (he had been treated
for cancer a couple of years previously).
Sometimes it is not possible to ascertain the cause. There is a
condition called "benign renal haematuria" which means there is bleeding from the kidneys
but the cause cannot be found. However, this is rare in cats.
Severe or
ongoing haematuria may cause or worsen anaemia, so you should always take
your cat to the vet if you see this symptom.
Pet Place has some information about
haematuria in cats.
This is a measure of the acidity/alkalinity of urine. A normal level is in
the range of 6.0 - 6.5. A cat with a urine pH higher than this (i.e. more
alkaline urine) can be at risk of developing struvite crystals, and a cat
with urine pH lower than this (i.e. more acidic urine) can be at risk of
developing calcium oxalate stones. A more alkaline urine may be a possible
sign of infection.
Pet Education mentions that normal pH for
cats is 6 - 6.5.
Glucose
Your
vet may wish to test for glucose (sugar) in the urine, particularly if
your cat has high
blood glucose
levels, in order to rule out diabetes.
Infections: Urinary Tract and Kidney
Infections (Pyelonephritis) Back to Page Index
Urinary Tract Infections
Urinary tract infections are relatively common in
CKD cats, so your vet
may run tests to check for their presence. As mentioned above,
cystocentesis is the
best way to obtain a urine sample if you want to check for infection.
Bacteria may be present, as may blood.
A test strip can show if there are bacteria present in your cat's urine,
which are indicative of an infection in a clean sample. Your vet may then
wish to run a culture and sensitivity test. This means that the laboratory
tries to grow the bacteria obtained from the urine sample over a few days
(3-4). If they are successful, they then treat each batch with a different
antibiotic to ascertain to which antibiotic the bacteria are most
sensitive (i.e. which antibiotic is most likely to kill the bacteria).
Urine cultures
(2002) is a paper from Antech Diagnostics which explains more about urine
cultures.
Your vet may also wish to run blood tests because infections sometimes
show in the white blood cell readings.
Even if your cat does not appear to have an infection, this may be a
false result. One human study,
Establishment of a persistent Escherichia coli
reservoir during the acute phase of a bladder infection
(2001) Mulvey MA, Schilling JD & Hultgren SJ Infection and Immunity69(7) pp 4572-9,
found that in some cases the bacteria that cause urinary tract
infections can burrow so deep into the bladder lining that they cannot be
detected in the usual tests.
In a later (2004) study reported by
Science Daily, researchers found that the
bacteria commonly involved in UTIs pass through four distinct
developmental stages, including a dormant stage in some cases which may
help explain why UTIs often recur.
Antibiotics should be given for around two
weeks. In order to be sure that the bacteria are completely eradicated and the
infection completely cured, some vets give CKD cats a prolonged course of
antibiotics, for four or five weeks or longer. Cats with a kidney infection
should always be given a lengthy course of antibiotics, see below.
Infections may sometimes lead to
anaemia, which
should also improve once the infection has gone.
Pyelonephritis means a kidney infection. Pyelonephritis usually occurs
because a urinary tract infection has risen into the kidneys.
In Chronic
renal failure (2001) Dr D Polzin states that
"infection at one location potentially places the entire urinary tract at
risk for infection."
Pyelonephritis may be acute or chronic. Cats with acute pyelonephritis
will often be obviously ill, e.g. not eating, sensitive to the touch, with
a fever. Unfortunately, cats with chronic pyelonephritis may not be
obviously ill. One of our cats, Harpsie, was prone to pyelonephritis and
he would simply be a little subdued. Fortunately, he also became
incontinent every time, so we were able to recognise the problem and get
treatment started promptly.
It is quite common for nothing to grow
in a culture if the cat has pyelonephritis rather than a lower urinary
tract infection,
particularly if the infection is chronic rather than acute. Some types of
bacteria do not grow in a culture.
The Merck Veterinary Manual
states
"A single urine culture can be negative if bacterial
numbers are low."
Ultrasound
may be helpful in diagnosing the existence of pyelonephritis,
though this can be of limited value in cats with
PKD, whose
kidneys already look abnormal. Ultrasound may also help with detecting urinary tract infections, but only
if the bladder is full. In both cases you need an experienced operator.
Urinary tract infection (UTI): how to diagnose
correctly and treat (2003), a presentation by Dr C Brovida to
the 28th World Congress of the World Small Animal Veterinary Association
mentions that
antibiotic treatment should continue for 4-8 weeks in the case of
kidney infections. The longer period is necessary because blood flow to the site of most kidney infections is poor,
so it can take a while for the antibiotics to reach and kill the bacteria. You should check the urine again 7-14 days after stopping the antibiotic
to make sure the infection has completely gone.
If your cat has
pyelonephritis, the bloodwork
may improve once the infection is under control.
Infections may sometimes lead to
anaemia, which
should also improve once the infection has gone.
The Veterinary Teaching Hospital at Colorado State University is seeking
volunteers for a study into the diagnosis of
pyelonephritis. The study will compare a new urine test to standard tests
to see if the new test might more accurately diagnose the infection.
Cats with pyelonephritis or a urinary tract infection
are eligible to participate, as are cats with suspected pyelonephritis,
but cats who have previously been given antibiotics are not eligible. The
laboratory tests required for the study and a kidney ultrasound will be
provided free of charge.
If you wish to participate, please call 970-297-5000 and say that you would like
to schedule an appointment for Dr Quimby's urine culture techniques study.
