Kidney disease is the single most common health issue in old cats, due primarily to the fact that cats are obligate carnivores and must eat meat to survive. This high protein diet places a tremendous workload on the kidneys, which can cause a gradual reduction in their function over time. The symptoms that we see from the outside are a cat who is losing weight and/or muscle mass, and who usually has a dry, unkempt coat of fur. Because kidney issues can cause nausea, we also see cats who may vomit, have diarrhea, or are less active than normal. You may or may not see changes in thirst or urination.
A veterinarian can diagnose kidney issues through a combination of a comprehensive physical examination and lab tests, which usually include radiographs, blood, and urine tests. In many instances, a veterinarian can actually feel a cat’s kidneys during the examination. If they are larger than normal, it can mean that an acute kidney problem like infection or stones is present; if they are smaller than normal, it usually means that kidney problems have been present a while.
The blood tests simply measure, among other things, the amounts of three metabolic products called BUN, creatinine, and phosphorus. Every time we eat or flex a muscle, these products are released into the bloodstream. It is the job of our kidneys to get rid of them. If our blood test shows that these substances are present in excessive quantities, we know that our kidneys are not working well. The higher the levels of these substances, the less function the kidneys have. We don’t even begin to see elevations in BUN, creatinine, and phosphorus until about 75% of normal kidney function is lost.
One of the common findings in kidney disease is the presence of protein in the urine. Under normal circumstances, our kidneys won’t let any protein into the urine at all. As kidneys begin to fail, they begin to let protein into the urine. This is one of the earliest ways to detect the beginnings of kidney problems– to measure the amount of small proteins in the urine. As we lose protein via the urine, two things happen. Because muscle is protein, we lose weight and muscle tone. Because our antibodies are protein, kidney disease causes immune suppression. Just not enough protein to go around.
The side effects of kidney disease also include high blood pressure and ulceration of the stomach and intestines. These are both due to the accumulations of toxins in the bloodstream.
Once a cat is diagnosed with kidney insufficiency, it is important to realize that most kidney function has already been lost. Our goals in treatment then become:
- To preserve, as best we can, the remainder of kidney function
- To minimize the secondary effects
- To maintain quality of life for the affected pet.
The approaches to kidney insufficiency in cats are dictated by the needs of the individual patient, but some general guidelines will serve as a starting point.
- Diet: The best way we have of preserving kidney function and minimizing the accumulation of the toxins mentioned above is to begin a cat on a prescription “kidney diet”. There are several out on the market, but in essence they reduce the amount of toxins formed by the cat, have a good quality of protein to help reduce muscle wasting, and have low salt to help prevent the high blood pressure. It is important to note that these diets not only help to TREAT kidney disease, we also think that they have a PREVENTIVE effect in older cats. So even if your cat does not have kidney problems now, it might not be a bad idea to begin them on such a diet to help head those problems off. When cats continue to lose weight, there are times that we must supplement their protein with a good quality meat such as low fat turkey/chicken or white fish such as halibut. Pork and beef products are not as good for these cats.
- If we are concerned about urinary protein loss, we can begin a cat on a medication called enalapril (or its cousin benazapril)l, which does two things: it helps reduce the protein in the urine, and it also helps both blood pressure and heart function.
- Because many of these cats’ immune systems are suppressed, we must often use antibiotics to prevent secondary bacterial infections. These are available in both pill and liquid form.
- If a cat’s stomach and intestines are irritated by the bloodborne toxins, we can use intestinal protectants like pepsid AC and other antacids to minimize ulceration. There is also an intestinal protectant that will help decrease the absorption of phosphorus from the intestines, which is a help since phosphorus is supposed to be excreted by the kidneys.
- There are times when we must try to increase urine flow. This is because if no urine is being formed, then no toxins can be excreted. We can do this by giving a cat diuretics like Lasix and/or by giving them fluids under the skin either in the office or at home.