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"Lucy" - Cat with chronic renal failure

Chronic renal failure (CRF) - more commonly known as kidney failure - is unfortunately all too common in our feline patients. Throughout life, all sorts of "wear and tear" can progressively damage the kidneys.

The kidneys have a large "functional reserve" - in other words, we do not need all of our kidneys to be in good working order to cope and perform all the required functions. Indeed, a patient can happily survive if one kidney needs removing. Thus, cats do not show any symptoms of kidney disease until at least two thirds of the kidneys are damaged.

Unfortunately, in CRF, we cannot reverse the damage that has been done; the best we can hope for is to try to help the remaining one third (or less!) of working kidney to cope as best it can, and also try to "stop the rot" - ie: slow down the rate of ongoing kidney destruction.

When "Lucy"'s owners noticed that she was drinking slightly more than normal, the possibility of kidney disease was foremost in their minds. Polyuria and polydipsia (excessive urination and thirst) are amongst the commonest signs of CRF.

I always tell clients that an increase in thirst should NEVER be ignored. Weight loss, vomiting, dullness and - in advanced cases - ulcers in the gastrointestinal tract and seizures are all symptoms of CRF.

Lucy's owners were vigilant and brought her in at the first sign of a problem. Blood tests showed that the levels of certain toxins in her blood (which the kidneys would usually eliminate from the body) were raised. This indicated that the kidneys were no longer functioning effectively. In early cases of CRF, there is much that can be done to help.

The mainstay of treatment involves feeding a diet that is low in protein and phosphorous. The toxins that accumulate in CRF are waste products from protein digestion. Thus, less protein means less wastes are produced, and the kidneys have less work to do excreting these wastes. Keeping the levels of phosphorous low is crucial as it slows down the advancing kidney disease. Unfortunately, cats love high protein foods, and some will not take to a low protein/phosphorous diet. We can still keep phosphorous levels controlled, however, even without a special diet, by giving drugs that prevent phosphorous being absorbed in the bowels.

As CRF progresses, the part of the kidneys which is still working tries to do the job of all the kidney tissue, so it "over works". This may seem sensible, but unfortunately, by working so hard, the remnants of normal kidney wear out even faster. A drug called benazepril is a recent advancement in the treatment of CRF as it reduces this "over-working" so that the remaining healthy kidney tissue lasts for longer.

Other important factors in treating CRF include monitoring of blood pressure. CRF can actually cause high blood pressure, and this is a vicious circle because high blood pressure hastens the kidneys' demise. Thus, cats with high blood pressure are put onto amlodipine - a human drug that reduces the pressure.

Finally, regular urine tests to monitor for urinary infections are important. Cats with CRF are more prone to water infections. Once again, there is a vicious circle, because infections add to the kidney disease.

In cats such as Lucy, where problems were detected early, the measures described may hold her kidney disease at bay for a long time. In cats where the disease is more advanced, it is not so simple. Human patients would receive dialysis and possibly transplants. Until recently, this was out of the question for feline patients. However, the Royal College of Veterinary Surgeons (RCVS) has recently approved theoretical proposals to allow kidney transplants to be performed in cats.

This has raised huge ethical questions. Unlike with man, a cat cannot give consent to donate a kidney, and moral arguments regarding the use of donor cats are understandably being raised. There is concern that cats may be bred purely to be used as donors.

One suggestion as a source of donor cats is rescue centres. An idea has been put forward that an unwanted or stray cat at a rescue center could be used to donate one kidney, and the owner of the recipient cat would then be obliged to give the homeless donor cat a home for life. This way, both the cat with kidney disease and the homeless cat would get a positive outcome.

Another concern is that the cat who has donated a kidney may well develop kidney problems of its own, much earlier than would otherwise have happened because it has less "spare" kidney tissue.

Should kidney transplants go ahead, they will be tightly regulated, and only performed at specialist centers with the required expertise (ie: you won't be able to steal a neighbours cat, pinch its kidney and get it implanted into your own cat at a back street clinic!!!). A transplant is likely to cost in excess of £8000! As far as I am aware, there have as yet been no transplants performed, but it would seem that - approve or not - it is just around the corner. Watch this space!

Geraldine Young BVSc CertSAM MRCVS

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