CHRONIC RENAL FAILURE IN CATS

We’ve prepared this handout to help you better understand chronic renal failure and its treatment. Chronic renal failure refers to a condition in which the kidneys have begun to lose their ability to produce concentrated urine and efficiently eliminate waste products. You can find much information on the web about renal failure and various treatments. Much of this information is probably accurate, but there is certainly an abundance of misinformation out there as well. Not all of these ideas, if accurate, will necessarily apply to all cats either. The progression of the disease seems to differ for each cat. Therefore, as we talk about care for your pet, we will tailor recommendations for treatment to your cat’s specific signs and symptoms. Not all cats will have the signs we will discuss, or necessarily benefit from all the treatments described in this handout, but hopefully we can give you an idea of what you might expect.

It can be very difficult to identify the cause of renal failure in cats. In general, about 67-75% of normal kidney function is lost before we see changes in clinical signs or blood work. There are probably a small number of cases that are the result of scarring from past illness or injury to the kidneys. Most cases, however, are probably “idiopathic,” meaning they have no known cause. There is evidence that the changes we see in the kidneys may be the result of aging. The fact of the matter is that cats are living much longer now with human care than they would if they were feral, or lived in the wild. This means that we are seeing more cats affected by age-related conditions, such as chronic renal failure, than before.

How Kidney Disease Causes Trouble

Many cats will experience weight loss, decreased appetite, and increased thirst and urination. Some will also have vomiting and/or diarrhea. Upon physical examination, we might note small kidneys in the abdomen, pale mucous membranes, and thin body condition.

One of the first functions the kidneys lose is their ability to concentrate urine. Cats then lose more water than they should, making them feel thirstier. Thus, drinking more is one of the first signs of renal failure. The kidneys are also an important filter for protein wastes (nitrogenous waste products) and electrolytes. When they are not functioning as efficiently as they used to, these waste products can build up in your cat’s circulation. The buildup of wastes can lead to a general feeling of malaise and nausea. This nausea partly explains the loss of appetite and weight we often see.

The kidneys are important not only for making urine and balancing electrolytes, but they also have important hormonal functions as well. They are responsible for producing a hormone called erythropoietin, which stimulates red blood cell (RBC) production. Thus, in long-term kidney disease, some cats can become anemic, or have decreased red blood cells, because the kidneys are not stimulating bone marrow to produce more cells.

The kidneys also normally filter out a hormone called gastrin. Gastrin increases acid production in the stomach, which, at normal levels, is necessary for digestion. When this hormone builds up, however, it signals increased acid production in the stomach, which can cause irritation, even

leading to ulcers. This problem can be exacerbated by irritation of the stomach and GI lining by the waste products in circulation. Vomiting and diarrhea can result.

Treatment

Unfortunately, this type of disease is not reversible, but there are many treatments we can try to keep your pet comfortable. We will want to monitor your pet’s kidney function through blood work and possibly urinalysis. The values that we follow indicate the progression of kidney disease, not necessarily how well or poor your pet should feel. Many cats have lab values that are out of the normal range, but still seem to feel fine.

For early or low-grade kidney disease, starting your cat on a low-protein diet is a good first step. Since the kidneys are responsible for filtering out the breakdown products of proteins, reducing the level of proteins in the diet is one way of cutting down the amount of work the kidneys have to do. Cats are by nature meat-eaters who are used to a diet high in protein, so some of them may not take to these diets quickly. Luckily there are a few different brands on the market, and usually between those, we can find one that your cat is likely to eat.

Some cats will benefit from fluid therapy, either through intense treatment here in the clinic via an IV catheter and/or long-term treatment at home using injections under the skin. Increased circulation of fluids and blood through the kidneys can help “flush” some of the increased waste products. If you think of the kidneys as a filter for blood, then even a poor filter such as kidneys in failure can still do the same work as normal kidneys if the amount of blood they are allowed to see is increased. Reducing the level of waste products through fluid therapy may help relieve nausea and lethargy.

Erythropoietin injections can be used to try to stimulate RBC production and thus help your cat’s energy level if he/she is anemic. We can administer these injections here, or you can learn to give them at home. However, roughly 25% of patients can develop antibodies to the injections, rendering them ineffective in the long run. Repeated checks of RBC counts here in the clinic are important, therefore, in detecting signs of antibody development.

Other medications that might be considered would be stomach protectants (Carafate / Sucralfate) and acid reducers (Cimetidine / Tagament, Famoridine / Pepcid). If your cat’s phosphorous levels are elevated, phosphate binders such as those found in antacids may be helpful as well.

Your cat will likely have good days and bad days. The goal we aim for is to keep the good days outnumber the bad. Please do not hesitate to ask us any questions or share with us any concerns you may have along the way.

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