The usual treatment for renal failure is a low-protein diet. This makes sense: proteins are the main source of nitrogen (vitamins contribute a negligible amount), and there is no urea or creatinine without nitrogen, so on a low-protein diet the levels of of these two compounds go down, meaning that (hopefully) the body is not poisoning itself as much. Even in a diet completely devoid of protein (not recommended), though, there will always be some protein breakdown as a part of "business as usual".
Unless you're a cat. If you're a cat, your metabolism, unlike those of your human slave-monkeys, is so attuned to the life of a carnivore that its preferred fuel source is not carbohydrates, but proteins. This means that for cats, protein is not just something that builds muscles and makes them strong--protein is also their main source of energy. To a cat, substituting protein with carbohydrates is like trying to run a diesel truck on jet fuel. It'll go--most likely with an explosive bang.
I realize that this doesn't really make sense--cats need to break down protein in order to build up carbohydrates so that their bodies can be properly fueled. Note the word "properly". Because cats are also extremely efficient at utilizing carbohydrates. Too efficient--the energy they cull from carbohydrates, if it's not burned off, is usually stored as fat. Even skinny cats may have a larger percentage of body fat than is strictly good for them.
For a cat with renal failure, then, protein is not the bane it is in the human counterpart of the disease. Protein is the fuel on which their bodies run most efficiently, meaning that there's less waste for the kidneys to filter, and giving them more energy to fight the disease. A diet high in carbohydrates, on the other hand, jacks everything up to hi-speed, too high--generating lots of waste and putting lots of stress on the kidneys.
So goes the theory, anyway. The reality is: it's complicated.
It's complicated because kidneys are complicated, and kidney failure even more so. It's not just the loss of filtering ability or concentrating urine. Kidneys generate erythropoietin, which stimulate the production of red blood cells. They regulate blood pressure--25% of the body's blood volume passes through the kidneys every minute. They regulate blood pH, calcium levels, sodium and potassium. Since renal failure isn't obvious until 70% of kidney function is lost, maintaining whatever kidney function is left becomes critical.
And it could very well be that decreasing azotemia at any cost may be the best course of action for this. I theorize that it has to do with the stage of the disease. If you caught it early--as I did (so early that the vet had to do a urinalysis to be sure)--then perhaps a diet of high-quality protein might buy you more time. As the disease progresses, perhaps low quantities of protein will be more important.
I'm not a vet. What I write is based entirely on my understanding of metabolism and biochemistry from my few years in medical school. Your vet will most likely think that my advocating a raw diet--which is not actually a high-protein diet, as meat is only about 20% protein--is heresy to begin with, and doubly so for a sick cat.
Yet the Tweeb is doing well. Questioning dogma is something I do regularly anyway, not necessarily with concrete evidence. To have a living, breathing, healthy counterpoint to accepted practice merely enforces what some might consider a bad habit.
Friday, May 8, 2009
When I adopted the Tweeb as a companion to Shadow (my other black cat), there was no reason to think that she had renal failure--a slowly progressive disease that is fairly common amongst elderly cats. Now, I knew she was old, as she'd been in "foster care" for six years. But she was healthy, for all her physical shortcomings--she has had no less than five broken bones in her little tough life, and most of them healed at odd angles, giving her the appearance of a Cubists' cat.
I'd been feeding Shadow a raw diet. Shadow was doing incredibly well on it, growing in leaps and bounds, and miraculously not getting fat despite my studio apartment being barely big enough for the two of us. The Tweeb took to raw instantly, too, much to my relief, chowing down enthusiastically on her bloody morass of ground chicken and organ meat.
But she was still drinking water.
That was the key: had she remained on her kibble diet, I would have thought nothing of the Tweeb drinking water, and would never have brought her in for the tests. Had she remained on kibble, I would not have realized that something was wrong until much, much later--possibly too late, when the sole choice remaining to me was not if euthanasia, but when.
Now, two years post-diagnosis, the Tweeb is doing quite well. She is energetic--perhaps even more so than Shadow, trotting after us when we go to the kitchen in hopes of begging a morsel out of us, and skittering through the apartment in a bout of the cat-crazies--and her appetite is undiminished. Far from losing weight, she's actually gained a significant amount of muscle and fat (not so much as to be anywhere near obese, but she's no longer the skin-and-bone kitty she used to be). She's quite personable, too, loving nothing better than to curl up on me when I sleep. You'd be hard-pressed to believe that she has renal failure, unless you were at the vet's with us.
I do not attribute this entirely to the raw food. Renal failure progresses differently in every cat, and it could simply be that she had the fortune to get the long-term variety. At the same time, though, it's hard not to believe that a diet of easily-synthesized protein, minimal carbohydrates, and plenty of water (in the form of meat and canned food) has nothing to do with her good health. I realize that the disease is progressive--that eventually we will have to give her more intensive care, along the lines of subcutaneous fluids and medications, and may even have to make that hardest of decisions concerning a rainbow bridge--but for now her renal failure seems to have been beaten into a sort of remission.
Next: the Great Protein Debate