Old, skinny cats

Published 9:55 pm Saturday, November 13, 2010

I saw an older cat today. I recommended blood work, but didn’t get permission. Still I started thinking about older cat problems.

Older cats get the same things that all cats get and several that older humans get. But older cats also get a set of diseases that cause them to lose weight and decline.

This set was called the triad of old cat diseases. Many cats that are older have one or more of these three diseases which can then be interrelated. Low potassium, kidney disease and hyperthyroidism makes up the triad.

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Hypokalemia or low potassium can be a sign of renal disease or a risk factor for it. Potassium should be absorbed from the food, but poor quality diets or diets that acidify the urine are risk factors. Cats with chronic renal disease are unable to prevent excessive potassium loss.

The potassium that is lost will be taken from the body tissues to maintain the blood levels. Cats with low potassium will often walk with their hocks down, have muscle wasting, weakness or pain.

Low potassium causes problems, but too much potassium causes cardiac arrhythmias and death. So, supplementation should always be under the advice and guidance of your veterinarian.

Chronic renal disease or kidney failure is another of the triad of old cats. Under normal circumstances, the kidneys continue to flush out all toxins out of the blood as long as there is 70 percent of the kidney still functioning.

If there is dehydration or stress or if the damage exceeds 70 percent, the toxins are not filtered out of the blood and build up and therefore poisoning the cat.

Cats with chronic kidney disease drink a lot and urinate a dilute urine. They may have muscle wasting and pain. The kidneys also secrete a hormone that tells the bone marrow to produce red blood cells. If the bone marrow does not get the hormone because the kidneys are not working, the red cells are not produced and the cat becomes anemic.

The final disease of the triad is hyperthyroid disease. This is where the thyroid gland produces too much thyroid hormone.

Usually the thyroid gland has a tumor, but not always. Thyroxin speeds up the body metabolism. The cat has a ravenous appetite, but cannot maintain weight.

The three diseases often interact. Increased blood flow from hyperthyroid disease will mean that the kidneys have more of an opportunity to filter toxins out of the blood.

But this increased metabolism puts an increased stress on the heart and blood pressure. Increased blood pressure damages many cells of the body, including the kidney. The increased blood flow can also increase potassium losses.

In short, the triad of cats becomes a juggling act of veterinary medicine.

In the very early stages a very satisfying juggling act, but in the later stages it can be quite frustrating. We probably will do blood work on this cat, but maybe not in time for me to be a hero.

MJ Wixsom, DVM MS MBA, Ashland, KY