[Paddypaws]

I think I asked a similar question of Hobbs not so long ago...
My understanding is that there is nothing in kidney....such as the high vit A in liver...that makes it dangerous to feed in reasonable quantities.
Now, we do all know about the ideal proportion of offal in raw being 5% but I have to say that I probably give mine a fair bit more than that as they REALLY like kidney, especially pig's.
I really would not advise anyone to play fast and loose with the recipe for a balanced diet, but the kidney is often a snack, an extra on top of their regular meals and also we do have to remember that most commercial wet foods, even some of those that we think of as better quality will be made up of a high proportion of offal ( Bozita lists lung as a main ingredient )