There are
a number of tests which can be run on a urine sample. Collectively these
tests are known as urinalysis.
The USG
test can help with the diagnosis of CKD, and may be useful for detecting
early CKD before it begins to show in blood tests.
The UPC
(urine protein to creatinine ratio) test can give some idea of the
severity of the CKD.
Urine
tests are also very important for helping to diagnose kidney and urinary
tract
infections.
What is Urinalysis?
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 of CKD. They are also used
to check for imbalances and infections.
Urinalysis and Urine Sediment (2004)
Christopher MM Presentation to the World Small Animal Veterinary
Association World Congress discusses urinalysis.
Obtaining Urine Samples
Urine samples may be obtained in a number of ways.
Some methods (free catch and non-absorbent litter) can be used at home and
you then take the sample to your vet for testing. Samples obtained in
this way are sufficient to run most of the tests discussed here, but are not sterile,
so are not suitable for running a culture and sensitivity test (see
below) to check
for infection. In this situation 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. If you are assessing the urine for the presence of
crystals, you need to take it in sooner:
Effects of storage time and temperature on pH,
specific gravity, and crystal formation in urine samples from dogs and
cats (2003) Albasan H,
Lulich JP, Osborne CA, Lekcharoensuk C, Ulrich LK & Carpenter KA
Journal of the American Veterinary Medical Association222(2)
pp176-179 found that "Storage
time and temperature did not have a significant effect on pH or specific
gravity" but "Urine
samples should be analyzed within 60 minutes of collection to minimize
temperature- and time-dependent effects on in vitro crystal formation."
Urine collection in dogs and cats
(2013) Hüttig A & The IRIS Board International Renal Interest
Society has information on the various urine
collection methods.
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.
Some people use a ladle, which means you don't need to
get too close to your cat. You can also buy sterile, individually
wrapped cups for this purpose from your vet or online. As with humans, you
should aim for a mid stream sample, i.e. let your cat urinate for a few
seconds before putting the cup in place. To maintain sterility, try not to
let the cup touch anything, such as your cat or the litter tray.
Rocket Medical
sell a sterile urine catcher called the Urikone which costs £69.60
for 50.
eBay UK sells two Uripots for £14.99 with free delivery.
Non-absorbent Litter
Non-absorbent 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 liquids, you can scoop up some urine to take to the vet.
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.
Nosorb
is one brand which 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.
Detection Litter
These are litters that change colour when they detect certain substances in a
cat's urine, such as blood.
Veterinary Practice News
(2008) explains more about how these products work.
Although these tests can give
you some basic information, e.g. the presence of blood or bacteria, if the
litter changes colour, you
should take a urine sample to your vet for proper analysis. The white blood
cell reading in the urine test itself is often inaccurate.
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.
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 it
is usually not appropriate for a cat who struggles at the vet's.
Urinary tract infection: how to diagnose and treat
correctly (2003) Brovida C
Presentation to the
World Small Animal Veterinary Association World Congress 2003 explains why cystocentesis is the ideal method of urine collection, but not
always possible.
Pet Place describes how cystocentesis is
performed.
The Various Urine Tests
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 because their kidneys' concentrating ability is
damaged, CKD cats usually have dilute urine.
A cat's USG level may change quite a lot
even over the course of
a day.
Before diagnosing CKD, therefore, the test should be run more than once
and other causes ruled out.
The USG test should also not be looked at in isolation, because it can
be affected by a number of things other than CKD:
Once a cat is receiving regular fluid therapy, this
test can be rather unreliable.
Cats with a dental problem known as
FORLs
sometimes have a low USG.
ACVIM consensus statement: guidelines for the
identification, evaluation and management of hypertension in dogs and cats
(2018) Acierno MJ, Brown S, Coleman AE, Jepson RE, Papich M,
Stepien RL & Syme HM Journal of Veterinary Internal Medicine 32(6)
pp1803-1822 says 'Unfortunately, increased BP may
induce polyuria (the so-called pressure diuresis), and thus the presence
of low urine-specific gravity (<1.030) in a patient with high BP does
not establish that kidney disease is present."
Using urine specific gravity (2015) Watson
ADJ, Lefebvre HP & Elliott J International Renal Interest Society
has information on the significance of USG in cats.
Azotaemia and urine specific gravity
(2008) Maddison JE Presentation to theWorld Small Animal
Veterinary Association World Congress explains more about USG.
Urine Specific Gravity (USG): How to Check
This test should be run by refractometer —
using the dipstick method is rather unreliable.
Advanced interpretation of the urine dipstick
(2010) Pressler B CVC in Washington DC Proceedings states ""Refractometers are the best balance between cost and accuracy for
measuring urine specific gravity. The best refractometers have different
scales for dogs and cats; however, if these are not available, the
differences are rarely clinically significant. Urine dipsticks are too
inaccurate to be clinically reliable for measurement of specific
gravity."
This is not
actually as simple as it first appears because "normal" depends upon a
number of factors, such as how much a cat is drinking, the weather etc.
USG therefore needs to be considered in conjunction with blood test
results and the cat's overall status.
The typical range for hydrated cats is around 1.035 to 1.060.
A cat with a USG below 1.035-1.040 is generally
considered to have a problem of some kind.
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.
Using urine specific gravity (2015) Watson
ADJ, Lefebvre HP & Elliott J International Renal Interest Society
says a normal level, where the cat is concentrating urine, is above
1.035.
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."
Urine Specific Gravity
Levels in CKD Cats
A USG level below 1.040 is considered low in cats.
Most
CKD cats have a much lower USG of between 1.008 and 1.012, which is known as isosthenuria.
Prolonging life and kidney function
(2007) Chew D & DiBartola SP Presentation to the 32nd World Small Animal
Veterinary Association Congress explains more
about this.
Of course, CKD is never simple, so occasionally a cat will have what
appears to be a normal USG yet have CKD.
Urine specific gravity (2015) Watson
ADJ, Lefebvre HP & Elliott J International Renal Interest Society
states: 'However, USG values in some cats with chronic kidney
disease (CKD) and azotaemia may be as high as 1.040 or 1.045, so kidney
disease could still be suspected in a cat if these values are
accompanied by persistent azotaemia.'
Urine Specific Gravity:
Other Causes When Low
A low USG may also be seen in cats with
the following conditions:
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
also 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(Protein
in the Urine)and the UPC
Ratio
Proteinuria (excess protein in the urine) is
an important consideration for CKD cats because it may make
CKD progress faster. It is also used to determine the stage of CKD.
One way of measuring proteinuria is by
measuring the
UPC ratio, which is the ratio of protein (in the urine) to the
cat's creatinine level (in the blood).
Please visit the
Proteinuria page for more information.
Obtaining a
urine sample via cystocentesis (a needle into the bladder) 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. "Benign renal haematuria"
is a condition in which 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.
See
above for detection
litters which may detect blood in the urine.
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.
Normally cats
do not have glucose in their urine.
However, this value may increase suddenly in cats because of stress, for
example in cats who get stressed or frightened at the vet’s.
Glucose may
also be elevated in cats with acute kidney injury.
Overview of feline bloodwork (2008) Jensen A 2008 Zimmer
Feline Foundation states "One way to differentiate between a
glucose spike due to acute stress and high blood glucose due to diabetes
is through urinalysis. If there is no glucose in the urine in the face of
high blood glucose, it may be due to the fact that the blood glucose has
not been high long enough to overflow into the urine, suggesting an acute
spike. This is not definitive, however. Presence of glucose in the urine
is, however, highly suggestive of diabetes."
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.
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
your link.