In searching around the web and looking at a cat memorial... the number of cats dying of renal failure is shocking. Years ago when I worked in an animal hospital in the city, this was a disease of old cats. Now I see people losing much younger animals to this disease. Anyone have any idea why it's becoming so common?
In searching around the web and looking at a cat ... disease. Anyone have any idea why it's becoming so common?

I don't know, but if I had to guess, it would be the food. Cheap, poorly made food, probably imported ... At least the meat and milk. I figure that if it doesn't hurt my kidneys, it probably won't hurt theirs.

I know the vitamin you mean but don't know where it can be bought. Duplicating a cats natural diet with raw meat would be difficult as they eat the entire carcass.
Cats can get into poison set out for rats and moes. This will cause renal failure. Cats or dogs can get heartworm and if they are going down hill it is part of the dying process. I read that the food cats and dogs get in the stores are not so good for them as they say it is and can cause cancers and etc. Again, if the cat gets cancer, renal failure is part of the dying process. They are saying to make your pet's food and add vitamins and suppliments.

If the food is not good, do you think the vitamins and suppliments are going to be any better? Will they be derived from anything different than the food is derived from? Then, don't forget the insectacides and pesticides can affect an outdoor cat who is in the environment containing these things. This can be a cause of young cats dying prematurly and renal failure. There is a number of speculations out there.
What about the bones. One could get stuck in their throat or intestines. Not good.

You have to be careful to not feed your dog chicken bones. Dogs tend to wolf food down, and small ... they will leave the bones in their dish uneaten. It's just in a cats nature to be a fastidious eater.

It's worth noting that wild-caught boney food is very different to cooked offerings from humans. Once bones are cooked, they tend to become hard and brittle, whereas uncooked bones are more bendy and much less brittle. Take the average fox and his stolen chicken from the hen house, for instance: he's perfectly able to cope with it. The domestic dog, however, (which is very closely related) mustn't eat chicken bones simply because they've been cooked and become brittle. This means they can splinter and tear the dogs throat and, especially, its stomach. Cats, should avoid fish bones, though. Very few cats naturally eat fish (too much trouble for the lazy 'baskets'!) so bones and even large scales can catch in the cat's throat.

It's really a shame. These two new shelter kitties we got last month will be house cats only. There are too many dangers out there to let them roam free even though we live out in the country.
I wonder how much the unnatural grain rich dry kibble foods they're being fed has to do with the obesity, diabetes and kidney failure rate in cats these days?!?!?!?! From what I'm reading about these foods, they're better suited to horses and cows than to obligate carnivores. :-\