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This Old Cat

Pets are living longer than ever and nowhere is this more evident than in the family cat. Once upon a time, a twelve-year-old cat was considered elderly. Even today, “reliable” sources, such as the PetMeds website, claim that a cat’s life expectancy is 10 to 14 years.

Balderdash! Your twelve-year-old cat may be no spring chicken, but it’s hardly an old coot. One doesn’t need to look very far to find kitties of 17, 18, or over 20 years of age. My oldest cat patient lived to be 26. Now THAT’S an old bird!

How do you help your cat live into its late teens or early twenties? You take care of it, of course! Old kitties have certain characteristic ways of deteriorating as they age. With a little forethought and anticipation the life expectancy of your aged kitty can be extended for years beyond what Mother Nature provides.

If you are a cat, and you live long enough, you will die of kidney failure. Why? Because it is the nature of cats to stress their kidneys, and kidneys wear out. Cats require a high-protein diet because of their obligatory carnivorous nature, and every amino acid subunit of every protein molecule generates at least one molecule of ammonia when it is metabolized. Ammonia is converted to urea by the liver, and then excreted by the kidneys. A cat’s kidneys work much harder than those of other animals.

Cats are born with amazing kidney function and have sometimes been know to survive for weeks without water. Feral cats, whose live-food diet is composed of roughly 90% moisture, are able to thrive with minimal drinking water available. Not so our modern housecats. Dry foods are generally formulated with about 10% moisture content. This means that the diet leaves the cat’s body wetter than it went in, and the cat must compensate by increasing the concentration of its urine to reclaim water. This is one of the reasons that cat urine is so stinky: The normal, everyday concentration of cat urine is vastly higher than anything a dog or human can possibly produce. No wonder they bury their pee!

To a young, healthy cat, this feat is no big deal. But the extra renal workload takes its toll and over the years, the number of functional renal filtration units will steadily decline. Fortunately, our kitties are born with at least five times as many functional units as they need. Still, when the number of functional units degenerates to about 20% of normal, a cat is no longer able to compensate and the levels of waste urea in the blood start to increase – but until this level of degeneration is reached it can be extremely difficult to tell that a cat has any deficiency at all!

Even when they can’t compensate, cats still compensate! The body has a special reflex that increases blood pressure generally and especially inside the remaining kidney filtration units, making them work even harder and helping to keep the cat’s waste levels where they belong. But this comes at a cost: the over-pressured filtration units burn out even faster and, even as our kitty fights to keep its kidneys working, it accelerates itself into hypertension, heart disease and advancing kidney failure, then uremic poisoning and death. This is the mechanism by which most older cats finally die.

Balderdash! It doesn’t have to be this way! Physiologic reflexes are based upon the assumption that everything is functioning normally, and that’s not the case when you’re running short on renal functional units, so this reflex has a deleterious effect. When your kidneys are marching towards failure, there’s a better way to handle the problem: better (and longer) living through pharmacology.

“ACE Inhibitors” are well tolerated, inexpensive, easy to use drugs, and - best of all - they counteract the adverse effects of renal compensatory reflexes that increase age-related kidney degeneration. ACE inhibitors open blood vessels to reduce systemic hypertension; decrease the damage high blood pressure generates in the heart, and increases blood flow through the remaining functional units to help them work better. ACE inhibitors dramatically slow the rate of kidney degeneration. For old cats with kidney disease, these drugs are cheap, safe, life-extension drugs.

We’re not talking small change here, but it’s hard to say exactly how much life extension takes place. I’ve heard experts claim that ACE inhibitors can double a cat’s remaining life expectancy. Some of my chronic renal degeneration patients just keep going and going, living three or four times longer than ever expected.

There’s a lot more to know about degenerative kidney disease, high blood pressure, and life extension in old cats. Talk with your veterinarian about what’s best for your senior kitty.

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