As the kidneys gradually lose their ability to regulate
and remove waste products effectively, these waste products build up in
the blood. This is called uraemia and can make a cat feel very unwell.
Generally speaking, cats with creatinine over 3 mg/dl
(US) or 265 µmol/L (international), will have problems with uraemia.
Controlling the CKD should help your cat feel a lot
better.
What is Uraemia?
One of the main roles of the kidneys is filtering the blood to
regulate and remove waste products or toxins. Kidneys damaged by CKD gradually lose their ability to
do this properly, so these waste products build up in
the blood: this is called azotaemia. This can make a cat feel very unwell,
and the clinical signs and symptoms that azotaemia causes are collectively
known as uraemia.
The
uraemic toxins which the cat's damaged kidneys are unable to filter
properly include
parathyroid hormone.
Contrary to popular opinion,
blood urea nitrogen (BUN) and
creatinine are not toxins themselves.
However, BUN levels correlate with uraemic toxin levels, i.e. if BUN is
elevated, it is highly likely that uraemic toxins (which are less easy to
measure) are also elevated.
Generally speaking, you will probably start seeing signs of uraemia in
cats with creatinine over 3 mg/dl (US) or 265 µmol/L (international) who
are properly hydrated.
ISFM consensus guidelines on the diagnosis and
management of feline chronic kidney disease (2016)
Sparkes AH, Caney S, Chalhoub S, Elliott J, Finch N, Gajanayake I,
Langston C, Lefebvre H, White J & Quimby J Journal of Feline Medicine &
Surgery18 pp219-239 state "Cats
with CKD suffer from nausea, vomiting and inappetence as a result of
uraemic toxins affecting the central chemoreceptor trigger zone." The central chemoreceptor trigger zone is the
part of the brain that amongst other things controls vomiting.
These
problems are so common in CKD cats that there is a page devoted to them.
Symptoms covered there include:
Some of these symptoms may also be seen in other manifestations of
uraemia, as discussed below.
Neurological Symptoms: Uraemic
Encephalopathy
Neurological symptoms are
sometimes seen in CKD cats, particularly as the CKD progresses and the
uraemia worsens.
Renal Disease
(2006)
Polzin DJ
Delaware Valley Academy of Veterinary Medicine
says
"Metabolic encephalopathies and peripheral neuropathies may occur in dogs
and cats with uremia. It is reported that as many as 65% of dogs and cats
with primary renal insufficiency/failure have neurological manifestations.
Of dogs with neurological signs, altered consciousness (31% of patients)
and seizures (29% of patients) were the most common signs. In our experience, acute onset of altered mentation is an
important neurological finding in dogs and cats with CKD that typically
heralds a poor short-term prognosis. Other common signs include limb
weakness, ataxia and tremors."
These may be
caused by the toxin levels.
Renal Disease
(2006)
Polzin DJ
Delaware Valley Academy of Veterinary Medicine
states
"Patients may develop what has been described as the "twitch-convulsive"
state wherein there is the simultaneous combination of tremor, myoclonus,
and seizures. In advanced CKD, patients may have neurologic signs that are
cyclical and episodic, varying from day to day. The severity and rate of
progression of neurological signs appears to vary directly with the
rapidity with which CKD develops."
If the
twitching is in the limbs, it may be termed peripheral neuropathy.
Other possible
causes of twitching in CKD cats include:
Pet MD mentions that twitching may be
caused by kidney disease.
Seizures
Occasionally, if toxin levels are really high (and
particularly if a cat is in
The Final
Hours), a CKD cat may have seizures. In such cases, reducing
toxin levels is essential in order to avoid permanent damage to the brain;
but this may not be possible if the cat is in his/her final hours.
Seizures may take a number of different forms. There
may be the classic jerking and loss of consciousness, but being "spaced
out" or mentally absent or staring into space may also be a type of seizure.
Other possible causes of seizures include epilepsy
or
a
brain tumour, but the causes mentioned
above are far more likely in a CKD cat and should therefore be considered
first.
Audiogenic reflex seizures in cats
(2016) Lowrie M, Bessant C, Harvey RJ, Sparkes A &
Garosi L Journal of Feline Medicine & Surgery18(4)
pp328-336 reports on
a particular kind of epilepsy called feline audiogenic reflex seizures
(FARS) which was recently identified in cats. This is most often found in
elderly (over 15) or Birman cats, and is triggered by high-pitched noises,
such as crinkling a paper bag or touching keyboard keys.
International Cat Care
explains more about this condition. Although phenobarbital
is usually used for epilepsy in cats,
Levetiracetam in the management of feline audiogenic
reflex seizures: a randomised, controlled, open-label study (2017) Lowrie M, Thomson S,
Bessant C, Sparkes A, Harvey RJ & Garosi L Journal of Feline
Medicine & Surgery19(2) pp200-206 found that a
medication called levetiracetam (Keppra) seems to work better for this
condition.
Seizures can be very scary to watch, but they are not thought to be
painful and often the cat does not even know it is happening. Cats may be
confused for a short while afterwards, but usually recover quickly. Many
cats have an increased appetite following a seizure so make the most of
this if your cat is a typical fussy CKD eater.
Howling (Particularly at Night)
This is
sometimes the result of toxin levels in the blood.
(2015) Gunn-Moore DA European Journal of Companion Animal Practice 25(3)
pp20-29 states "Chronic kidney disease can result in increased vocalisation when
associated systemic hypertension
causes cerebral vascular compromise (as in CDS). It can also occur when
polyuria without adequate access to water cause cerebral dehydration,
when polydipsia/polyuria predisposes to a secondary UTI (see UTI), or
when severe uraemia results in uraemic encephalopathy."
Gastrointestinal Symptoms
Gastrointestinal symptoms may also be seen in CKD cats as follows, though
these are less common than vomiting, nausea and appetite loss:
If the
uraemia is particularly bad, the cat may develop gastrointestinal
bleeding.
Nutritional management of chronic renal disease
Fascetti AJ & Delaney S University of California at Davis says
"The
waste products may also enhance blood loss by leading to the formation of
gastrointestinal ulcers and a reduction in blood clotting ability."
Unfortunately this is often not easily detectable, though it may sometimes manifest itself as
diarrhoea.
Renal Disease
(2006)
Polzin DJ
Delaware Valley Academy of Veterinary Medicine
says "Uremic
enterocolitis, manifested as diarrhea, may occur in dogs and cats
with severe uremia ...when present, uremic enterocolitis is often
hemorrhagic.
Considerable gastrointestinal hemorrhage may initially escape clinical
detection."
Dark stools
are also a possible sign, as is vomiting blood. Occasionally, however,
dark stools are caused by iron supplements.
If you
suspect gastrointestinal bleeding, you should take a stool sample to your
vet for occult blood testing (when I did this for Ollie, I was the first
client who had ever requested this test; but it was positive). See
Diagnosis for more on how to test for gastrointestinal bleeding.
CKD cats
with this problem do not normally need to be treated in hospital.
If gastrointestinal bleeding remains untreated,
anaemia may result.
Pet Place has some information about
blood in stool (melena).
Although
uncommon, diarrhoea
may sometimes be seen in CKD cats secondary to the CKD.
Renal Disease
(2006)
Polzin DJ
Delaware Valley Academy of Veterinary Medicine
says "Uremic
enterocolitis, manifested as diarrhea, may occur in dogs and cats
with severe uremia, but it is typically less dramatic and less common than
uremic gastritis. Owners of 80 cats with spontaneous CKD did not report
diarrhea. However, when present, uremic enterocolitis is often
hemorrhagic.
Considerable gastrointestinal hemorrhage may initially escape clinical
detection."
Other possible
causes of diarrhoea in a CKD cat include:
a sudden
change of food, perhaps to a
therapeutic kidney diet. It is better for a cat's
digestive system if a new food is introduced gradually - mix some of the
new food with the old and gradually increase the amount of the new food
in the mix over a period of several days.
food
intolerance. Because the goal is to reduce protein levels, some
therapeutic kidney foods may have relatively high levels of
carbohydrates, and some cats who are used to a higher protein diet may
find these harder to process. Introducing the new food gradually may
help, but some cats are simply grain-intolerant.
cats taking
antibiotics may develop diarrhoea. If you think this might be the
cause, contact your vet and ask if you can switch to a different
antibiotic. Please do not just stop the antibiotic, however, or the
infection may return with a vengeance.
too much
lactulose
or MiraLAX, given to treat constipation, may
cause the opposite problem of diarrhoea. It is better to start lactulose
at a low level and increase as necessary.
sometimes people think
their cat has really runny diarrhoea, but in actual fact, the cat is
constipated and the runny liquid is all that can squeeze out round the
solid stool. This is known as "overflow incontinence".
So do be aware of this possibility, particularly if there is only a
small amount of liquid faeces.
malabsorption problems and parasites
are other possible causes.
Whatever
the cause,
you must see your vet
if the
diarrhoea lasts longer than a day or so, both to
ensure your cat is OK (diarrhoea may cause or worsen
dehydration) and for a proper diagnosis.
I am sometimes asked about stool colour and texture. Sometimes I am even
sent unsolicited photos of cat stools. Ah, the joys of running this site.
Pale stools may indicate a lack of bile, which is sometimes a sign of
liver disease. Green stools may indicate rapid transit through the small
bowel.
Here are some links on the different colours, sizes and textures of cat
poop. I uploaded these just after eating a rather gooey chocolate brownie.
Bad move.
Pets Canada
discusses the colour and consistency of cat stool.
The high
levels of urea seen in CKD cats are released into saliva. An enzyme in the
bacteria in the mouth called urease interacts with the urea and produces a
very strong and distinctive odour. It is hard to describe the aroma,
though once smelled, never forgotten. It is sometimes described as being
an ammonia smell (like bleach) but it may smell more like urine (ammonia
is a constituent of urine), though neither description really captures the
smell.
This smell will
often be particularly noticeable if the cat
crashes.
If your cat's breath smells more like nail polish remover,
this may indicate
The toxins
produced by the body can cause ulceration of the gums, which occurs when
the uraemic waste is converted by the bacteria in the mouth into ammonia
(hence the smell of the cat's breath being described as ammonia-like
above). You may see ulcers in the cat's mouth if you look inside, or
in severe cases your cat may
vomit blood (which may
also be a sign of bleeding from further down the
gastrointestinal tract).
You may also see drooling. Some cats paw at the mouth (which can also be a
sign of dental
problems).
Mouth
ulcers are very painful and often lead to a lack of appetite, or,
even more distressingly, a desire to eat coupled with an inability to do
so — the cat may approach the food bowl and sniff the food, then walk
away.
The ABCs of veterinary dentistry: U is for ulcers —
what a pain! (2019) Bellews J
DVM360 has some good photos of ulcers and states "ulcers are wounds." As
somebody who is prone to mouth ulcers (I got my first one at the age of
four), to such an extent that I was treated for them by a dental hospital
for sixteen years, I can tell you that this is 100% true. Ulcers are
agonising.
Check
inside your cat's mouth regularly for inflamed gums or ulceration or ask
your vet to do so. I am sometimes asked what mouth ulcers look like. They
are usually a small area of white or yellow, sore-looking skin with a thin
red ring around it.
(2014) Niemiec BA Today's Veterinary PracticeJan/Feb 2014
discusses other possible causes of ulcers.
Teeth Grinding
Cats who
grind their teeth may have excess stomach acid.
Dental problems
are another possible cause. It may also be a sign of
dehydration. This sign is sometimes seen in cats with
pancreatitis.
Very rarely this may be a sign of a rare condition called Feline Orofacial Pain Syndrome
(FOPS), which is a pain disorder predominantly seen in Burmese cats.
Feline orofacial pain (FOPS)
(2009) Rusbridge C has some information about this condition.
Some CKD
cats have a distinctive aroma, which is caused by the levels of toxins in
the body. It is similar to the
bad breath aroma. You may
notice an increase in this aroma or it may develop for the first time if
your cat's bloodwork is worsening.
In some
cases, you may first notice this smell when your cat
crashes.
Thomas developed this smell seemingly overnight when he crashed, but after
treatment it gradually disappeared.
Itching
This may be
a uraemic itch caused by the levels of toxins in the blood.
Pruritus in certain internal diseases
(2007) Yonnova D Hippokratia11(2) pp67-71 mentions that
itching occurs in about 15% of uraemic human patients, so if your cat is
scratching a lot or grooming excessively, consider this possibility.
Other
causes of itching in CKD cats include:
high phosphorus
levels, particularly if the high phosphorus levels go untreated,
resulting in
occasionally liver problems; if this is the case, your cat's bloodwork
should show elevated liver values.
If your cat
actually pulls out fur rather than merely scratching, this may indicate
hyperthyroidism.
Itching, particularly on the face, may also be a side effect of a
medication called
methimazole, which is used to treat hyperthyroidism.
Uraemic Hypothermia
It has long
been known that hypothermia (a reduced body temperature) may be seen in
human CKD patients, which occurs in part because the kidneys produce more
than 10% of body heat.
Hypothermia in uremic dogs and
cats (2016) Kabatchnik
E, Langston C, Olsen B & Lamb KE Journal of Veterinary Internal
Medicine30(5) pp1648-1654 looked at the records over sixteen
years of cats who underwent haemodialysis in NYC and found that 38% of the
cats with elevated kidney values had hypothermia. It concludes "In
cats, UH seems to be a more prevalent phenomenon driven by uremia."
Hypothermia is also often seen in anaemic cats. See
Anaemia for
tips on keeping your cat warm.
Treatment Options
It
is possible to treat all of the above symptoms, in many cases effectively,
and details can be found in the
Treatments section.
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.
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