CHRONIC KIDNEY FAILURE
What is meant by the term "Chronic Kidney Failure"?
The term "chronic kidney failure" suggests that the kidneys have stopped functioning
and are, therefore, not making urine. However, by definition, kidney failure
is the inability of the kidneys to remove waste products from the blood. This
definition can occasionally create confusion because some will equate kidney
failure with failure to make urine. Kidney failure is NOT the inability to make
urine. Ironically, most dogs in kidney failure are actually producing large
quantities of urine, but the body's wastes are not being effectively eliminated.
When is this likely to happen in my dog?
The typical form of chronic kidney failure is the result of aging; it is simply
a "wearing out" process. The age of onset is related to the size of the dog.
For most small dogs, the early signs occur at about 10-14 years of age. However,
large dogs have a shorter age span and may go into kidney failure as early as
7 years of age. In some breeds there is a genetic predisposition to kidney failure.
What changes are likely to occur in my dog?
The kidneys are nothing more than filters. When aging causes the filtration
process to become inefficient and ineffective, blood flow to the kidneys is
increased in an attempt to increase filtration. This results in the production
of more urine. To keep the dog from becoming dehydrated due to increased fluid
loss in the urine, thirst is increased; this results in more water consumption.
Thus, the early clinical signs of kidney failure are increased water consumption
and increased urine production. The clinical signs of more advanced kidney failure
include loss of appetite, depression, vomiting, diarrhea, and very bad breath.
Occasionally, ulcers will be found in the mouth. When kidney failure is accompanied
by these clinical signs, it is called uremia.
How is chronic kidney failure diagnosed?
The diagnosis of kidney failure is made by determining the level of two waste
products in the blood: blood urea nitrogen (BUN) and blood creatinine. The urinalysis
is also needed to complete the study of kidney function.
Although BUN and creatinine levels reflect kidney failure, they do not predict
it. A dog with marginal kidney function may have normal blood tests. If that
dog is stressed with major illness or surgery, the kidneys may fail, sending
the blood test values up quickly.
Since this is basically just a wearing out process, can it be treated with
anything other than a kidney transplant?
In some cases, the kidneys are worn out so that they cannot be revived. However,
with appropriate treatment many dogs will live for several more months or years.
Treatment occurs in two phases. The first phase is to "restart" the kidneys.
Large quantities of intravenous fluids are given to "flush out" the kidneys.
This flushing process, called diuresis, helps to stimulate the kidney cells
to function again. If enough functional kidney cells remain, they may be able
to adequately meet the body's needs for waste removal. Fluid therapy includes
replacement of various electrolytes, especially potassium. Other important aspects
of initial treatment include proper nutrition and drugs to control vomiting
What can I expect from this phase of treatment?
There are three possible outcomes from the first phase of treatment:
1. The kidneys will resume functioning and continue to function for a few
weeks to a few years.
2. The kidneys will resume functioning during treatment but fail again as
soon as treatment stops.
3. Kidney function will not return. Unfortunately, there are no reliable
tests that will predict the outcome.
If the first phase of treatment is successful, what happens next?
The second phase of treatment is to keep the kidneys functioning as long as
This is accomplished with one or more of the following, depending on the situation:
1. A low protein diet. This helps to keep the blood tests as close to normal
as possible, which usually makes your dog feel better. Also, once kidney disease
is advanced, a decreased protein diet will decrease the workload on the kidneys.
2. A phosphate binder. Phosphorous is removed from the body by filtering
through the kidneys. Once the filtration process is impaired, phosphorous begins
to accumulate in the blood. This also contributes to lethargy and poor appetite.
Certain drugs will bind excess phosphates in the intestinal tract so they are
not absorbed, resulting in lower blood levels of phosphorus.
3. A drug to regulate the parathyroid gland and calcium levels. Calcium and
phosphorus must remain at about a 2:1 ratio in the blood. The increase in blood
phosphorus level, as mentioned above, stimulates the parathyroid gland to increase
the blood calcium level by removing it from bones. This can be helpful for the
sake of the normalizing calcium:phosphorus ratio, but it can make the bones
brittle and easily broken. Calcitriol can be used to reduce the function of
the parathyroid gland and to increase calcium absorption from the intestinal
tract. This is recommended if there is evidence of abnormal function of the
A drug to stimulate the bone marrow to produce new red blood cells. The kidneys
produce erythropoietin, a hormone that stimulates the bone marrow to make red
blood cells. Therefore, many dogs in kidney failure have a low red blood cell
count, or anemia.
How long can I expect my dog to live?
The prognosis is quite variable depending on response to the initial stage
of treatment, your ability to perform the follow-up care and your dog's willingness
to eat the special diet. Treatment can be effective. Many dogs will have a good
quality of life for months or even years.
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