Cats — Kidney Failure (Chronic)

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What is meant by the term "Chronic Kidney Failure"?

Presumably, the term "chronic kidney failure" suggests that the kidneys have stopped working 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 cats 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 cat?

The typical form of chronic kidney failure is the result of aging; it is simply a "wearing out" process. For most cats, the early signs occur at about 10-14 years of age.

What changes are likely to occur in my cat?

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 cat from becoming dehydrated, due to increased fluid loss in the urine, thirst is increased so the cat drinks more water.

Thus, the early clinical signs of kidney failure are increased water consumption and increased urine production. The clinical signs of advanced kidney failure include loss of appetite, depression, vomiting, diarrhea, and very bad breath. Occasionally, ulcers will be found in the mouth.

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. If the values are much higher than a normal cat, a diagnosis of kidney failure is given. A 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 cat with marginal kidney function may have normal blood tests. If that cat is stressed with major illness or surgery, the kidneys may fail, sending the blood test levels quickly into the abnormal range.

Since this is basically just a wearing out process, can advanced kidney failure be treated with anything other than a kidney transplant?

Yes it can. You must recognize that your cat's kidneys have reached this point due to aging, so they will never be normal again, but many cats still have enough functional kidney tissue so treatment can be very rewarding. Treatment of advanced kidney failure is 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 and diarrhea.

What can I expect from this phase of treatment?

There are three possible outcomes from the first phase of treatment:

• The kidneys will resume functioning and continue to function for a few weeks to a few years.

• The kidneys will resume functioning during treatment but fail again as soon as treatment stops.

• 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 possible. This is accomplished with one or more of the following, depending on the situation:

• A high quality, low protein diet. This helps to keep the waste products as low to normal as possible, which usually makes your cat feel better.
   

• Potassium supplementation. Potassium is lost in the urine when urine production becomes excessive. A potassium supplement will replace that loss. Low potassium levels have been shown to further reduce kidney function. This is the second reason that a potassium supplement is recommended. Potassium supplements come in tablet, powder, or gel form.
   

• A phosphate binder. One of the secondary things that occurs in kidney failure is an elevation of the blood's level of phosphorus. 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.
   

• Fluids given at home. Once your cat is stabilized, fluids can be given under the skin (subcutaneously). This serves to continually "restart" the kidneys as their function begins to fail again. This is done once daily to once weekly, depending on the degree of kidney failure. Although this might not sound like something you can do, you will be surprised at how easily the technique can be learned and how well most cats will tolerate it.
   

• 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.
   

• 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 cats in kidney failure have a low red blood cell count, anemia. Epogen, a synthetic form of erythropoietin, will correct the anemia in most cats. Unfortunately for some cats, the drug cannot be used long term because the immune system recognizes the drug as "foreign" and will make antibodies (immune proteins) against it.

How long can I expect my cat to live?

The prognosis is quite variable, depending on response to the initial stage of treatment and your ability to perform the follow-up care. However, veterinarians encourage treatment in most situations because many cats will respond and have a good quality of life for months to years.