Hi,your intutition would tell you a lot, in this case-- as, for example, the sense you have that the kidneys are not quite better. I would be inclined to take some kidney-strenghtening/cleansing herbs First, to give the kidneys some nutritonal support, so to speak, before taking on a water fast. I'm not sure what "mild kidney disease" really is, or what numbers mean, but I had nephritis as a child--and one of my kidneys apparently stopped growing, so it is half the size of the other. (or was) I've not seen pictures of this, but my doctor way back then said they waved, like leaves in the breeze. I was a medical anomaly, and she told me then to always drink a GALLON of water a day. Apparently this (waving) is not the norm, which probably leaves them susceptible to bruising and so on.
But just recently, I read in The School of Natural Healing (Dr. Christopher's Herbal manual)where he said he's seen children's kidneys "torn loose" from what people were calling a spanking. . Since then I've been deliberately loving my kidneys. :-)
See what Chris says, according to the source. Alkso, you might want to check in the Truth in Medicine forum, ask HV about kidney herbs...or Barefoot: but he's offline for a short while, i think.
One of the very finest things for the kidneys is young coconut water--the fresher and real-er the better. In fact, it is THE healer. You might do a fast on coconut water (not canned though), and really do your kidneys a great favour.
It is a universally perfect food.