I will follow up when I know results. On Internet I saw some opinions that low back issues are not rare in low t community
Well, lower back issues, i.e. spinal and muscle could tie into what I wrote above. (I'm not saying with you though.)
Kidney is a whole different story. If there is a kidney link, I'd like to know that for obvious reasons. Again, the only thing I know is through the above hormone link which ties into red blood cell production.
Now I did mention on one of my pages that if you have existing hypertension, some men can have increased blood pressure. Obviously, this could affect the kidneys long term. I'm not sure about pain however.
But, otherwise, I don't see many connections...