Groin wound granulated for months--won't heal after various treatments...Suggestions?

I'm sorry you haven't had a reply to your question sooner. It can be quiet here over the weekend sometimes.

The first thing that comes to mind for me is if your cat is able to access this wound as licking it?   I have a friend whose cat had a persistent wound on the inside back leg and it was very difficult to heal because of his licking the area (they did manage to get it healed eventually I am pleased to say).   Without the ongoing presence of the bacteria perhaps this is a contributing factor?

Very much hope you find a solution.   

Did the Vet SA their is still bacterial found in that sight?  If so, is there some sort of topical ointment that could be applied?  I guess the issue here is as MServant stated, in that he can lick it off, so it needs to be kidney friendly  because that area would be fairly impossible to bandage or cover, and not sure you want to stress him with a cone of shame .  I know one thing people sometimes use with a hard to heal wound is Colloidal Silver, so you might give it a try just to see, if you've given up on everything else.

Sounds as if you've really got the kidney issues under control  Congrats on that.  I recently lost my kidney cat after 3 years of it.  (3rd one )  Love the fact that you're using hard boiled egg whites.  I used to mix in raw egg whites into my girls canned food since she liked hers nice and soupy.  Added GOOD protein and helped diffuse some of the phosphorus in her food.  I just couldn't get her to eat them cooked, even scrambled in a little unsalted butter, silly girl.

When you start having questions about CKD, here is my "go to":  http://www.felinecrf.org/index.htm  I usually referred to that website before Vet visits, etc.  so I was well prepared with all my questions about treatments, etc.  They aren't interactive, but do have plenty of info.