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 a) to preserve, as best we can, the remainder of kidney function; b) to minimize the secondary effects, and c) 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. You might also want to check out our web page on The Integrative Treatment of Kidney Disease.