Compromised kidneys benefit from a diet reduced in phosphorus. In theory, feeding a basic low-phosphorus diet works nicely, but reality can differ, and especially in cases of home-prepared diets. Here's why:
Say you find a diet that's being touted as great for dogs in kidney failure. This diet might even have a low phosphorus content, and the correct calcium to phosphorus ratio (it should be 3:1 in the case of kidney failure). Assuming the rest of the diet is balanced, you should be good to go, right? Maybe. What if the diet is meant to provide the correct nutrients for a 3 day period, and your dog happens to need to eat this amount over a 2 day period, or there's some other change? Bottom line is that more, or less food = greater, or fewer amounts of nutrients. These include phosphorus, and the calcium to phosphorus ratio that is so critical in these cases. So, a generic diet is not in your dog's best interest, even if it seems great on paper. The reality of the dog is what matters, and it's only when the diet is formulated specifically for that dog that it works as well as it can.
What about dogs that have other issues as well as kidney trouble? A diet formulated to meet individual needs can best address a combination of problems and challenges.
Diets that address kidney disease should not include plant-based oils. Although these oils are fine for healthy kidneys, they can create damage once kidney function is compromised. Yet, I've seen generic diets and even Rx diets that include them.
Here's an example of why understanding what works and what doesn't is so important. I recently read the following which is not optimal for your dog, but claims to be. It states that to calculate the amount of calcium a dog needs we should use a dose of 1,000 mg per 1,000 calories fed. In other words, 1 mg of calcium per calorie fed. Then we should multiply this amount by the number of calories the dog consumes per day. Stay with me here! Using this directive (don't do it), my Tori who consumes 400 calories per day would need 400 mg of calcium daily. However, when I work through her actual, individual requirement based on ideal body weight, calcium should be fed as 548 mg daily. This difference matters not only for the healthy dog, but impacts a diet meant to help the kidneys by enough that the entire thing can backfire. If we were to base calculations on the information above, Tori's calcium requirement would be considered even less if she became less active, yet her actual, individual need hasn't changed. Nutrient requirements don't change based on how many calories a dog eats, and this is why generic diets can become problematic so easily.
The very best diet for dogs with kidney trouble is one that is formulated for that one dog, and considers age, activity level, all health issues...a fully individualized approach.
The Reasoning Behind These Supplements
Supplements that support and target certain aspects of health and disease are important, and I rarely suggest using anything that isn't specific. There are a lot of claims without very much evidence that we could spend money on, and when dealing with a sick animal, I like to keep things simple. There's not much point to asking compromised kidneys to deal with things that aren't going to benefit in the first place. Here are the items I use and the reasons I use them:
Wild salmon oil: omega 3 fatty acids are friendly to the kidneys, add a source of fat that makes food more tempting (an important fact for dogs that start to turn away from food), and provide vitamin D. The vitamin D aspect is extremely important. Read this to learn the why and how of this fact.
Kidney dysfunction can be an underlying cause of urinary tract infections (and vica versa), so I want to prevent more trouble for these dogs. The most common bacteria in UTI is e.coli, and this particular combination of D-Mannose and cranberry has produced outstanding results. It's not just about the combination, but the purity and ratio of one to the other.
CoQ10 helps people with kidney problems via a protective effect, but studies in dogs are not available. Nevertheless, I've used this supplement for about 12 years in most of my kidney diets and found it to help. The product on my site is a dry version and people sometimes wonder why it's not in oil since CoQ10 is fat-soluble. People take supplements with water, but we add supplements to a dog's food which provides the fat required to begin with. There seems to be no point to spending more money for the same result. The biggest factor is quality of product rather than an oil carrier when we feed dogs.
"It's hard not to immediately fall in love with a dog who has a good sense of humor"
~ Kate DiCamillo