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Cats with Kidney Insufficiency:

Kidneys are vital to life and kidney failure is a common cause of death in cats. When asked 'how long do cats live?' I tend to reply that a cat is as old as its kidneys. There is a new treatment which can delay failure of the kidneys as long as it is started during the phase of kidney degeneration called 'insufficiency'.

When an animal is born it has about 4 times as many kidney units (called nephrons) as it needs. These nephrons get damaged by a variety of processes and eventually, when 75% of them have been destroyed, there is only just enough kidney function left. Beyond this point, the animal is said to suffer from kidney insufficiency. It will seem quite normal, but urine samples will start to show abnormalities.

If not treated, there tends to be a vicious circle effect whereby the body tries to keep up kidney function by increasing the blood pressure and this causes damage to the delicate filter beds which are at the top of each nephron.

By controlling the blood pressure within the nephron it is possible to slow down the continuing damage and extend life expectancy. There is a class of drugs called ACE inhibitors which block the system causing increased blood pressure. Some work in the kidneys to protect the filter beds.

In a trial where the effects of the ACE inhibitor was compared to placebo (ie no drug but dummy pills), there was a marked improvement in survival of cats receiving the drug compared to those given placebo. This graph (courtesy of Novartis Ltd) illustrates the difference in survival in days of the two groups of cats:

The important point here is that treatment needs to be given during kidney insufficiency, whilst the cat appears outwardly completely normal. The only way to detect kidney insufficiency is to examine a urine sample. Blood samples will give normal results until kidney failure develops, and then it is too late to make a big impact on the cat's life expectancy. I recommend testing urine samples from all cats over 10 years of age annually to attempt to find the cats which would benefit from the treatment and gain extra life before their kidneys fail.

An American site, felinecrf.com dedicated to the subject of Renal Failure (not insufficiency) has copious information. Not all methods/treatments are available in the UK. The Feline Advisory Bureau have some information also.

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