Gosh, I wish I had more experience in this area so I could make some suggestions - and I just don't, dang me.
I *think* some good folks to PM might be Yorkieluv and EllieMay - if I recall, I think both of them are good with kidney issues. I think you'd want low-protein bc otherwise the kidneys would be quite busy and working hard. I would recommend PMing these folks bc often times they'll then get a notice in their emails that they have a PM at YT.
I wish I could be of more help!!!!! If I think of anyone else who has kidney experience, I'll post it here...
Thanks Marci, for pointing me over here.