In a nutshell:
1) I recommend thermal imaging to everyone, even just for prophylaxis.
2) I am now thinking about kidneys in relation to POIS, this had never crossed my mind so far.
Infrared thermography is a very easy, quick, and non-invasive way to scan the body for abnormalities. Areas with inflammation simply show up as warmer. The method is cheap as well. I had searched for the word "infrared" here on this forum, but had not found any results, so I guess not many members of the forum have done such a screening and perhaps this would be of interest.
The infrared camera showed clearly that my right kidney was warmer than my left one, so there is something wrong with it. I was directed to see a nephrologist so they can do an ultrasound. I've never noticed any distinguished symptoms related to kidneys specifically.
I just a did a super quick search online - kidneys are responsible for so many functions, just like the liver. They produce a bunch of hormones, interact with toxins, etc. etc. I also searched this forum for "kidneys" - they have been mentioned here and there but without too much discussion.
Let's see if we get somewhere from here.