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Most veterinarians are under the impression that "high" protein causes a progressive decrease in kidney function as animals' age. As a consequence of this thinking, low protein diets are often suggested and prescribed for geriatric animals. The conclusion has been deduced from studies in rats, which have shown high protein diets may cause kidney lesions. Additionally, it is known that once animals have kidney disease, protein restriction may help alleviate signs.

However, it does not logically follow that an experimental result on one species of animal, in this case rats, can be extrapolated to other species. Secondly, the fact that protein restriction helps in pre-existing kidney disease does not equate to protein being an etiological cause of kidney disease.

In one study, thirty-one dogs were divided into two groups and studied for four years after they had reached seven to eight years of age. Half of the group was fed a diet consisting of 34% protein and the other half received 18% protein. To make the animals even more susceptible to kidney changes, the researchers removed one kidney. (Such cruel experimentation was totally unnecessary. The logic of the Wysong Optimal Health Program™ philosophy would have easily predicted the answers.) The results: six dogs in the 18% protein group died, whereas only one in the 34% group did. Examination of kidney tissue showed no significant difference between the two groups in terms of kidney degeneration or disease. The fact that neither group experienced significant kidney disease, but that the group on the lower protein diet experienced a higher mortality may speaks to the beneficial effects on the immune system of a higher protein diet.

An added finding in this study was that higher dietary levels of phosphorous did not contribute to kidney disease since the diets used in this study were at 0.9% phosphorous, whereas those commercially available for treatment of renal failure are at 0.3% phosphorous.

Moreover, consider that kidney disease in pets fed starch-based processed diets is not seen to any extent in wild animals. Wild animals of all ages consume high protein muscle and organs from their prey.

Further evidence regarding the cause and prevention of kidney disease:

Protein may not be a factor in slowing the kidney disease progression--

"...Restriction of protein intake does not alter the development of renal lesions nor does it preserve renal function." (See KIRKS VETERINARY THERAPY XIII, Small Animal Practice, W. B. Saunders, page 861). The effect of protein restriction on the progression of renal damage in dogs and cats remains controversial and no definitive study exists on this matter. Not enough protein in the diet can be equally detrimental and protein malnutrition in patients with renal failure can facilitate the occurrence of other complications or lead to an early death. Studies have revealed that protein restriction made no difference at all in longevity. The effect of dietary protein restriction alone on the progression of chronic renal failure is either minimal or non-existent.
Ingredients and processing dramatically influence the quality of the protein in mixed processed pet foods. The poorer the quality of the protein and the more it is processed, the more "junk" protein must be excreted by the body putting stress on the kidneys. Studies have shown that there is an inverse relation between the blood urea content and the biological value of the diet. The more meat and organs, and the less they are processed, the less "junk" protein must be excreted by the kidneys. The Wysong Au Jus™ canned varieties, as well as the Wysong TNT™ (true non-thermally) processed raw cat and dog foods such as Archetype™, UnCanny™, and Dream Treats™ that have been minimally processed are of the very highest biological value.
Chemicals in food (like preservatives, coloring agents, artificial flavoring agents, and the toxins created by processing) and in the environment (contaminated water, air and soil) are directly stressful to the kidneys. These factors are the likely candidates for precipitating kidney disease, not the natural high protein diets carnivores have adapted to over eons.
High blood pressure in the kidney deteriorates the organ rapidly. A decrease in blood pressure can thus slow the progression of kidney disease. Studies have shown that supplementation with dietary omega-3 oils provides renoprotective effects in dogs with subtotal nephrectomy. Proteinurea & histologic injury (glomerulus) were less in dogs receiving fish oil. Omega 6 oils - usually in abundance in processed pet foods - are proinflammatory and increase kidney glomerular pressure and filtration rate. Omega-3s in Wysong Pet Foods and cat and dog supplements thus can help retard the onset or progression of kidney disease.
Probiotic bacteria in the gut hydrolyze urea to ammonia and incorporate it into their own protein. When the bacteria are passed in the feces, along with them go the nitrogenous wastes rather than being absorbed and having to be excreted by the kidneys. Wysong probiotics help facilitate this process. (See Probiosyn™)

References
Canine & Feline Nutrition, second edition, by Case Carey & Hirakawa Daristotle.
Managing a renal crisis by Martha S. Gearheart, DVM, Diplomate, American board of Veterinary Practitioners
Nutritional management of chronic renal failure (CRF) in Dogs & Cats by Dennis J. Chew, DVM, Diplomate ACVIM (Internal medicine), Ohio State University, College of Veterinary Medicine, Columbus, Ohio & Patricia A. Schnck, DVM, PhD, Michigan State University, College of Veterinary Medicine, East Lansing, MI.
Geriatric Nutrition: Protein; Purina Research Update
Kidney failure & diseases in the dog & the cat at ThePetCenter.com