Dr Sarah Caney, ex-FAB Lecturer
renal failure (CRF) is a common cause of illness in older
cats. Unlike some other organs such as the liver, damage to
the kidneys cannot be repaired. Signs of renal disease are
usually seen once at least 70-75% of the renal tissue has
been irreversibly damaged and, once established, CRF is generally
a naturally progressive condition. The rate of progression
of disease can vary hugely from cat to cat. There is no cure
for CRF and in people with this condition, dialysis treatment
followed by renal transplantation are the main options. Neither
of these treatments are currently available in the UK , although
it is possible to improve the quality of life of affected
cats by employing a variety of medical treatments tailored
according to the individual's needs. In recent years many
treatment advances have been made and there are now more options
available to owners wishing to care for their cats with CRF.
Before discussing these treatments in detail, it is important
to consider what normal kidney function is and therefore the
range of problems that cats with CRF may have.
normal cats, the kidneys play many vital roles which include:
Elimination of waste products from the
body via the urine
Regulation of the body's acidity, electrolyte
levels (calcium, phosphate, potassium, sodium and chloride)
and water balance
Production of hormones such as erythropoeitin
(required to stimulate production of red blood cells by the
bone marrow) and renin (important in controlling water and
Activation of vitamin D (important in
control of blood calcium and phosphate levels)
of CRF develop when two thirds to three quarters of renal
function has been lost. Cats with CRF are vulnerable to problems
Accumulation of protein breakdown products
(including urea and creatinine which can be measured in blood
samples) which is associated with clinical signs of illness
(e.g. nausea, vomiting, loss of appetite)
Acidosis (increased blood acidity)
Anaemia (partly due to lack of production
High blood pressure (systemic hypertension)
cats often show non-specific signs of ill health such as a
variable or poor appetite, weight loss, depression and sickness.
An increased thirst is seen in about one third of cats with
CRF although this clinical sign can also be seen with various
other conditions common in middle aged and elderly cats such
as hyperthyroidism and diabetes mellitus (‘sugar diabetes').
Diagnosis of CRF therefore requires collection of blood and
urine samples for analysis. Most commonly a diagnosis is made
following identification of azotaemia (accumulation of the
protein breakdown products creatinine and urea in the blood)
and loss of urine concentrating ability (i.e. the urine is
more dilute than it should be). Further tests may be required
in some cats to identify the cause of the renal disease. For
example ultrasound examination of the kidneys is usually a
straightforward technique for identification of polycystic
kidney disease (PKD).
of cats with CRF involves a range of treatments tailored according
to the individual's needs.
is the ideal diet for cats with kidney problems?
is common to prescribe specific dietary therapy since this
has been shown to improve the quality of life and survival
of cats with CRF and may reduce the rate of progression of
disease. Renal diets typically have restricted levels of high
quality protein which limits the amount of protein breakdown
waste products for the ailing kidneys to excrete. Levels of
phosphate are also restricted since cats with CRF have a tendency
to retain excess amounts of this in the body which can contribute
to their feeling unwell. Renal diets have increased amounts
of potassium and B vitamins which CRF cats are vulnerable
to losing in their urine and increased numbers of calories
which helps CRF cats with a poor appetite to maintain a normal
body weight. Renal diets usually have lower levels of sodium
in them which may help to reduce the risk of high blood pressure
is possible to prepare home cooked diets for cats with CRF
and veterinary recipes are available for this purpose. Most
owners do not elect for home cooking protocols as this is
very time consuming and therefore not a practical option in
with CRF often have a poor appetite and this can be exacerbated
by offering special kidney diets which may not appeal to the
cat. In some cases, the use of appetite stimulants such as
the anti-histamine cyproheptidine (trade name Periactin) or
anabolic steroids can be helpful in stimulating an adequate
appetite. More recently some vets have been treating cats
with persistently poor appetites by placing a feeding tube
into the stomach. Feeding tubes can be placed into the stomach
using endoscopy and are referred to as PEG tubes when this
is done (percutaneous endoscopically placed gastrostomy tube).
Although an anaesthetic and short period of post-operative
hospitalisation is required to place the tube, once in place
these can be used for prolonged periods to administer food,
liquids and medicines to the cat.
can dehydration be treated and prevented?
with CRF are vulnerable to becoming dehydrated since they
are unable to produce concentrated urine. Encouraging cats
to drink and maintain normal hydration is helpful, if possible,
and moist diets are probably preferable. Offering flavoured
water may encourage cats to drink more (e.g. fish broth) although
it is important to not offer salty liquids as these can increase
the risk of high blood pressure and other problems developing.
Many cats with CRF do however prefer the dry kidney diets
and it can be difficult to encourage drinking. Recently, one
treatment that is receiving a lot of attention is administration
of fluids under the skin by the cat's owner (subcutaneous
fluid therapy). This is not currently a common recommendation
in the UK although many USA owners of CRF cats are finding
it a simple and valuable technique for helping their cat.
In severe cases, dehydration may require treatment with intravenous
fluid therapy (i.e. cat admitted to a veterinary surgery and
placed on a drip). Giving additional fluids at home can therefore
be helpful in preventing this. In addition, extra treatments
such as potassium can be added to the fluids. Subcutaneous
fluid therapy usually involves giving around 150 ml of fluid
under the skin twice a week. The technique is well tolerated
by most cats and owners include one report of a 19 year old
cat with CRF that has been managed for 6 years using subcutaneous
fluid therapy as part of the management protocol. If necessary,
the regime can be changed to more frequent fluid administration.
The owner will be trained in how to perform this technique
by a veterinary surgeon or nurse – it is important that the
fluid is given correctly in a sterile manner so that infections
do not occur at the site of injection. Some cats do not tolerate
this procedure and so it may not be suitable for all cats
with CRF. One new innovation that has recently been developed
is a special catheter that is surgically placed under the
skin and can stay in this location for up to one year so that
fluids can be given without the cat feeling any discomfort
of a needle.
can electrolyte problems be treated and prevented?
are salts present in the body which are required for normal
cellular functions. The most common electrolyte imbalances
in CRF cats involve potassium and phosphate. CRF cats are
vulnerable to losing potassium in their urine which can cause
a reduction in the blood potassium levels (hypokalaemia).
Hypokalaemic cats can become very weak and lose their appetite.
Although renal diets contain increased amounts of potassium
in them, some cats with CRF can still develop low blood potassium
levels. Additional potassium can be supplied to these cats
as a powder or tablet.
cats are vulnerable to accumulating phosphate which can make
them hyperphosphataemic (have high blood phosphate levels).
Oral phosphate binders are drugs which bind to phosphate present
in the diet and limit what is absorbed by the cat's bowel.
These drugs may be needed in CRF cats whose blood phosphate
levels stay high in spite of dietary therapy or in those cats
that will not eat a prescription diet.
can systemic hypertension be treated and prevented?
blood pressure (hypertension) occurs in 20 – 30% of cats with
CRF and can have serious consequences such as blindness. Monitoring
of blood pressure is therefore important so that high blood
pressure can be identified and treated rapidly where it occurs.
Most practices now have facilities to measure blood pressure
in cats and this is a technique which is simple, pain free
and only takes a few minutes to perform. In those cats requiring
treatment, anti-hypertensive drugs (such as oral amlodipine
or benazepril) can be prescribed. Most cats need once daily
therapy to maintain normal blood pressure.
other treatments may be needed?
treatments which may be prescribed according to the needs
of the cat include:
Erythropoietin: Anaemia is common in
cats with CRF and one reason for this is the decreased amounts
of erythropoietin produced by the kidneys. Erythropoietin
is a hormone that triggers red blood cell production by the
bone marrow and treatment of anaemic CRF cats with human erythropoeitin
can be helpful in reversing the anaemia. Unfortunately, this
treatment can be expensive and may not always have a lasting
effect as the human hormone is recognised as a foreign substance
by the cat's body which eventually produces antibodies to
the drug preventing it from having a useful effect. Another
possible side effect of this treatment is development or exacerbation
of high blood pressure so cats receiving this treatment need
to be carefully monitored. There is research underway in two
US universities to develop a feline erythropoietin which would
be much more helpful and should not result in antibody production
by the cat.
Iron supplementation: Some anaemic CRF
cats are iron deficient so measuring iron status and considering
iron supplementation may be useful. Iron is required in production
of haemoglobin, the oxygen carrying molecule in red blood
Anti-sickness pills for vomiting: cats
with CRF may suffer from what is known as uraemic gastritis
(inflammation of the stomach due to retention of waste products
and hormones which the kidneys normally excrete). Anti-sickness
treatments including antacids and anti-vomiting drugs can
be very helpful at treating this problem which may help the
cat to feel much better.
Calcitriol (vitamin D therapy). Although
still somewhat controversial, many clinicians have
used this treatment in certain selected CRF patients and found
it beneficial at maintaining normal blood levels of calcium
ACE (angiotensin converting enzyme) inhibitors
such as benazepril (Fortekor®, Novartis): This treatment
has recently been advocated based on research in people with
CRF in which ACE inhibitors were found to increase the survival
times. Preliminary data from a recent clinical trial in cats
with CRF suggests that cats receiving this therapy have a
better quality of life (as assessed by their owners) and a
reduction in the amount of protein they lose in their urine.
There may be a small benefit in terms of an increase in survival
time, although the trials have not yet been completed and
a significant increase in survival has not been proven at
this stage. Fortekor did not appear to reduce the parameters
used to assess renal function (e.g. blood urea and creatinine
levels). However, a specific group of cats with CRF which
are losing large amounts of protein in their urine do appear
to show a clear response to this treatment (better survival,
appetite and weight gain) although this accounts for only
a small proportion of cats with CRF. ACE inhibitors also lower
the blood pressure and so may be prescribed as anti-hypertensive
Antibiotics: recent studies showed that
up to 30% of cats with CRF suffer from a bacterial cystitis
at some point in the course of their disease. In some cats
this infection may spread to the kidneys further compromising
the renal function. In other cats, the bacterial cystitis
may be caused by a bacterial infection of the kidneys (pyelonephritis).
Cats with CRF may be more vulnerable to the development of
bacterial urinary tract infections since the urine they are
producing is so dilute. Unfortunately, in many cases the bacterial
infection does not cause signs of cystitis (such as urinating
more frequently, straining to urinate and passing bloody urine)
which makes diagnosis of this complication difficult. Diagnosis
requires collection of a urine sample which is assessed for
microscopic evidence of bacteria and inoculated onto bacterial
culture media for growth in a laboratory. A course of antibiotics,
in some cases for weeks or months, may be needed to successfully
eliminate bacterial urinary tract infections.
medications not discussed may be required in some cats with
CRF and it is important to modify the treatment according
to the specific requirements of each individual cat.
is the prognosis for cats with CRF?
long term outlook for cats with CRF is very variable ranging
from a few weeks post diagnosis to many years. CRF is believed
to be a progressive condition in most, if not all, cats although
the rate of progression may vary considerably according to
the cause of the disease and other individual factors. The
prognosis is also affected by other issues including whether
the cat has any other medical problems which influence its
condition and how severe the consequences of renal disease
are. For example, cats with anaemia caused by CRF often have
a very poor long term prognosis as this is difficult to treat
effectively for long periods of time. Owner and veterinary
monitoring of affected cats helps to assess the severity of
disease and rate of progression which ensures that affected
cats receive all of the treatments that they need to help
maintain good health. Care of affected cats at home can be
very rewarding as well as helpful in ensuring that CRF patients
have the best quality of life for as long as possible.
Books available: Caring for a cat with kidney failure by Dr Sarah Caney, priced £16.95
This is a book written in a way that everyone from a cat owner upwards can understand. Its been designed to be a complete guide to kidney failure in cats - from receiving the bad news and dealing with emotional issues, through to diagnosis, treatment and monitoring, to euthanasia and bereavement advice. There is also a glossary of veterinary terms and a case report.
'10% of the profits made from the sale of the book will be donated to the Feline Advisory Bureau to help them to continue the excellent work they do for cats'