"Kidney failure" might mean compromised, overworked kidneys - or it might mean damaged kidneys (i.e., severe, chronic renal failure).  Kidneys can be damaged - irreparably, so the veterinary information says - by a whole slew of environmental poisons and veterinary treatment drugs, and via other disease forces as well (such as kidney infections, diabetes, leptospirosis, cancer, as examples).  And kidney problems can be inherited (especially by certain breeds).  (By the way, I've read that kidney failure is supposedly easier to treat in cats than in dogs.)  Kidney failure (renal disease - increased thirst, dehydration, loss of appetite, urination changes, maybe nausea and pain) is common in elderly pets - systems do fail as we get older, whoever we are.  But the kidneys are one of the critical factors in eliminating toxins from the body - and they become less efficient with age, and with toxin loading.  (Which can be a problem at any age, just like with humans.)" more on kidney failure

Russell Swift, DVM on kidney disease - "Fortunately, since I have turned to a holistic approach to wellness, I have seen many dogs and cats outlive their death sentence by years. I believe there are three major reasons for kidneys to degenerate and eventually fail: 1) poor quality nutrition, 2) toxicity and 3) chronic disease. I have discussed in many previous articles the failings of processed foods. Inadequate and improper protein sources and low moisture content (of dry foods) are the two major kidney stressors I believe occur in commercial foods. The kidneys also take a hard hit from many toxins to which the body is exposed. Many conventional medications, notably nonsteroidal anti-inflammatories and certain antibiotics, are very damaging to the kidneys. Ultimately, there is not much known about the long-term effects of many food additives and preservatives; fluoride in the drinking water; and all the pesticides and herbicides used in, on and around our companion animals (and ourselves!). Item number three on the list above is a term used by homeopaths to describe a chronic disturbance in the body's function that results in symptoms. Diet  in controlling Chronic Renal Failure (CRF)

When I am confronted with a dog or cat who has been diagnosed with  chronic renal (kidney) failure (CRF), I generally begin by educating the animal's guardian about the dangers of commercial foods and the benefits of fresh-food feeding. Conventional veterinarians are under the misunderstanding that low protein diets are the best way to feed an animal with chronic renal failure. My experience is that such an approach will lead to the death of the animal in a few months (thus bringing their prognosis to fruition). I have found that just the opposite approach is the most effective for most animals. I suggest feeding a high protein, raw-meat-based diet. I have seen dramatic reductions in elevated kidney blood tests within two weeks in some patients. Why does conventional medicine do the opposite? Because all of the conventional nutrition research is done with processed foods. I haven't seen any done with raw foods. I believe this is the reason for the research data. Heat-treated animal protein, as found in commercial foods, is more difficult to digest. This results in more protein (nitrogen) waste, which the kidneys must remove from the bloodstream. Blood urea nitrogen (BUN) is a protein waste that is measured in a blood test. Therefore, a diet that has high levels of cooked protein is more stressful to the kidneys and results in higher toxicity (BUN) in the blood if the kidneys are not functioning well. Raw protein, in comparison, digests more completely with less waste. This results in more protein for healing and rebuilding tissue without the renal stress. Remember, by nature carnivores eat a very high protein diet. They should have the ability to handle it. Another benefit of the raw foods is that they contain much more water than dry foods. This helps the kidneys discharge waste material. I would not be writing this information if I had not seen many animals improve on such a regimen. Other holistic vets are having the same results." read more

Diet in controlling Chronic Renal Failure (CRF)
In the past, it was believed that a low protein diet was essential in controlling Chronic Renal Failure (CRF).  The idea behind this is to cut down on the kidneys' load.  However, studies done on dogs in renal failure, show that a low protein diet did not help the GFR or BUN of said dogs.  Since cats have an even higher protein requirement than dogs, it seems unlikely that they could thrive on low protein diets. As an obligate carnivore, they need the nutrients only available from meat.  So one has to walk a fine line between making sure all the kitty's nutritional needs are met, and keeping the stress on the kidneys as low as possible. more info

I would suggest that with the kidney problem you need not use nearly as much silver as would be the case for cancer. A couple of tablespoons to an ounce a day in the water would be fine.