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Chronic
Renal Failure in The Dog
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THE PET HEALTH LIBRARY
By Wendy C. Brooks, DVM, DipABVP
Educational Director, VeterinaryPartner.com
http://www.VeterinaryPartner.com
Kidney Failure (Chronic
Renal Failure)
What You Should Know
If My Pet Is Still Making Plenty of Urine, How Can There Be Kidney Failure?
In chronic kidney failure, urine is usually produced in excessive quantities.
What the kidneys are failing to do is conserve water (they are failing
to make concentrated urine). The body produces numerous toxins on a moment
by moment basis. These toxins circulate to the kidneys where, dissolved
in water, they are filtered out and urinated away. An efficient kidney can
make a highly concentrated urine so that a large amount of toxin can be
excreted in a relatively small amount of water.
When the kidneys fail over a long time period, they lose their ability
to concentrate urine and more water is required to excrete the same amount
of toxin. The animal will begin to drink more and more to provide the failing
kidneys with enough water. Ultimately, the animal cannot drink enough and
toxin levels begin to rise. Weight loss, listlessness, nausea, constipation,
and poor appetite become noticeable. It is common for animals, especially
cats, to have a long history of excessive water consumption when they finally
come to the vet's office with one of the latter complaints.
What Is my Veterinarian Reading on the Blood Panel?
If you wish to understand your pet's status with regard to kidney
failure, it is important to understand some of the parameters being monitored.
Urine Specific Gravity - This is a measure of how concentrated
a urine sample is. Water has a specific
gravity of 1.000. A dilute urine sample has a specific gravity less
that 1.020 (often less than 1.010). A concentrated urine sample would have
a specific gravity over 1.030 or 1.040.
Blood Urea Nitrogen (BUN) - This is a protein metabolite
excreted by the kidney (it is one of the toxins we are concerned about).
In a normal animal, the BUN is 25 or so. A good goal for BUN in kidney failure
is 60 to 80. Often at the time of diagnosis, BUN is well over 150, 200, or
even 300.
Creatinine- This is another protein metabolite (though this one
is less dependent on dietary protein intake than is BUN). A normal creatinine
is less than 2.0. A good goal in kidney failure is a creatinine of 4.5
or less. BUN and creatinine will be tracked (as will several other parameters)
over time and in response to different treatments.
Phosphorus - The calcium/phosphorus balance becomes deranged in
kidney failure due to hormone changes that ensue as well as the inability
of the failing kidney to excrete phosphorus. If calcium and phosphorus
levels become too high, the soft tissues of the animal's body will develop
mineralized deposits which are inflammatory and uncomfortable. The bones
will weaken as well. If phosphorus can be maintained in the normal range
(less than 7.5), a medication called calcitriol can be used to help prevent
or slow the progression of kidney failure. Medications and special diets
can be used to help keep phosphorus levels down.
Potassium - The failing kidney is unable to conserve potassium
efficiently and supplementation may be needed. Signs of hypokalemia (the
scientific name for low blood potassium) include weakness, especially drooping
of the head and neck.
Packed Cell Volume/Hematocrit - This is a measure of red blood
cell amount. More literally it represents the percentage of the blood made
up by red blood cells. The hormone that stimulates the production of red blood
cells is made by the kidney. The failing kidney does not make this hormone
in normal amounts and anemia can result. Anemia is often worsened by the
extra fluid administrations needed to manage the kidney toxins. Sometimes
a blood transfusion is needed or, more commonly, the owner of the pet must
learn how to give hormone injections to boost the red blood cell count.
Blood Pressure - Blood pressure is not something measured off
a laboratory result sheet but it is important to monitor in kidney patients
as there is a tendency for hypertension to develop in kidney failure. Special
medications may be needed to manage this problem should it arise.
The owner who plans to be involved with monitoring of the pet's condition
at home should become familiar with these terms and even get a copy of
the pet's lab results for their own records.
Your veterinarian is likely to have a handwritten chart in your pet's
record showing changes in the above parameters; it's not a bad idea to start
your own folder and chart at home.
What Are the Treatment Options?
What one does to address this problem depends on its stage at the time
of diagnosis. More advanced
cases will require hospitalization for a cycle of diuresis. Fluids are
delivered intravenously for 48 to 72 hours and the above parameters are rechecked.
The goal is to stabilize the patient at a toxin level where good life quality
can be indefinitely experienced.
Milder cases can be managed with fluid administration under the skin
(subcutaneous fluids) at home. This sounds scary at first but, in fact,
it is not uncomfortable for the pet and is easy to learn.
Also available (but very expensive) are dialysis, where a machine filters
the toxins from the patient's blood, and kidney transplantation.
What Sort of Treatments Might my Pet Require at Home?
Special Diet:
Most prescription diet companies produce a diet with restricted protein
(so as to generate less BUN),
restricted phosphorus, and with other important qualities to promote
metabolic health in kidney patients. Many clinics stock K/D diet made by
Hills and Select Care Modified made by Innovative Veterinary Diets. In some
cases, simply switching to this food may be adequate treatment. There is no
preventive benefit that we know of in changing to these diets prior to the
onset of kidney failure.
Amphojel/Phosphate Binders:
Amphojel is an antacid caplet used for stomach upset in people.
It also binds phosphates in the diet when it is given with food. This reduces
the phosphorus intake from the GI tract and helps normalize the blood phosphorus
level.
Calcitrol: This medication actually represents activated vitamin
D. Vitamin D is not a vitamin in the way other vitamins are or in the way
we think of vitamins; vitamin D is actually a hormone. It plays an important
role in calcium phosphorus balance and is beneficial in preventing the
progression of kidney failure when it is administered while phosphorus
levels are still normal. Our experience with this medication has been excellent
and we recommend its use in appropriate patients whole-heartedly. The doses
that are used are exceedingly small and must be compounded by a special
pharmacy. If your pet qualifies to take this medication, special instructions
on how to obtain it will be given to you.
Epogen/Erthropoeitin: In older times, anabolic steroids were used
to address the anemia (low red cell count) of chronic kidney disease. With
the advent of genetic engineering, the actual hormone the kidney has stopped
producing can be given by injection. This is done usually at home 2 to
3 times a week along with an oral iron supplement. This treatment has helped
many patients dramatically as the anemia that goes with kidney disease can
be very debilitating. The downside to this treatment is that the product
commercially available for use is of human origin and pets will ultimately
produce antibodies against it (and worse still against their own remaining
hormone). For this reason, this hormone is not used until anemia is more
advanced and the patient really needs this treatment.
Amlodipine (brand name Norvasc): It is difficult to find a blood
pressure medication that is not also toxic to the kidneys. Amlodipine is
a calcium channel blocker type medication commonly used in hypertensive cats
with renal failure. It also must be compounded specially in cat sized doses.
Fluids Under the Skin: This technique is important to learn as
most pets in kidney failure require this treatment either right away or following
hospitalization. If this process is recommended for your cat, you will receive
lessons on how this technique is performed.
Kidney failure is a complicated disease with many
facets. Please do not hesitate to contact your veterinarian should you have
questions or problems at home. You will periodically be contacted when it
is time for your pet to have monitoring tests.
You Are Not Alone: Further Resources
Chronic renal failure is a common disease and there are many pet
owners just like you all sharing thoughts, tips, and information over the
internet. If you are interested in exploring these resources, here is what
is available:
A large information area has been structured at http://www.felinecrf.com/ by the owner
of Avatar, a cat who ultimately succumbed to his kidney failure. While
this site is especially geared for cat owners, its information is certainly
applicable to dog owners as well.
For those with America On-Line subscriptions, there is a weekly feline
chronic renal failure chat to which all are welcome. This chat is held
on Sundays from 5 to 6 pm Pacific Time in the private room called "crf."
(Click on "People Connection," click on "Private Room," type in "crf.")
There is also an on-line mailing list (a listserv) for owners of cats
with chronic renal failure. To subscribe go to http://groups.yahoo.com/group/Feline-CRF-Support/.
Please do not hesitate to ask your veterinarian if you have any questions
or problems regarding your pet's condition.
Copyright 2001 - 2007 by the Veterinary
Information Network, Inc. All rights reserved.
This work was originally published by Veterinary Information Network,
Inc.(VIN)
and is republished with VIN's permission.
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The above information is simply informational. It's intent is not
to replace the advice of a veterinarian nor to assist you in making a diagnosis
of your pet. Please consult with your own veterinarian for confirmation of
any diagnosis. Your pets life may depend on it.