You are right, but not in very young dogs and cats... also, the crappy food is one reason dogs and cats are suffering renal failure at younger and younger ages.. and what do vets do — limit the protein when that is exactly the wrong thing to do (as evidenced by a researcher at of all companies Purina a few years ago and presented at a seminar on pet health).
Acute renal failure is actually more common in young dogs and cats, because they’re more active and more likely to get into poisons around the house and garden. Chronic renal failure is usually age-related, but there’s no evidence that it’s related to food, except in the few cases where it’s secondary to diabetes (actually secondary to hypertension, which is often secondary to diabetes), which can be caused by feeding obligate carnivores a high-carb diet. I have an ancient cat who has been diabetic for 2 years and in chronic renal failure for 4 years. Needless to say, his renal failure is not secondary to diabetes, and the diabetes actually appeared a few months after I switched him to a very high protein diet (heavily supplemented Gerber’s all-meat baby foods), though there’s no reason to suspect a connection.
I participate in a large internet group devoted to chronic kidney failure in cats, and have never seen any evidence or even suspicion voiced, that kidney failure is appearing at “younger and younger ages”. My cat was 17 when he was diagnosed with very early stage, still asymptomatic kidney failure. The veterinary nephrologist who is a consultant to the group (and who is a vet school professor who teaches nephrology) has never indicated any suspicion of a connection between high-carb foods and kidney failure. In her lecture notes, which are posted online, she lists the causes of renal damage as: “immune-mediated inflammation, infection, ischemia, nephrotoxins, congenital abnormalities, heredofamilial abnormalities, trauma, postrenal obstruction, neoplasia, hypertension, diabetes, electrolyte disturbances” http://www.vetsites.vin.com/Kidney/CRF.doc
There are a lot of good reasons to feed cats and dogs high protein diets, but warding off kidney failure isn’t one of them.