I was worried about my kidneys & how narcotics affect them so I asked my PM about it earlier this week. He told me not to worry about it.
I've looked up some info on the NLH (National Library for Health) site. It seems it depends on which specific opioid(s) you have been using. They break down in different ways. Fentanyl (what I take), for example, is inactive & non-toxic by the time it reaches the kidneys and is generally considered safe to use even in people with pre-existing renal failure.
It could be entirely unrelated to the opioids, though. When I had that problem, my PCP had me tested for diabetes/pre-diabetes. I tested negative, but I did have an elevated blood glucose level. Once I cut down on sugar, cut out spicy food & started PT, I improved significantly after the first few weeks. I don't remember how old you are, but my PCP told me this is a fairly common problem as women get to be around 30 (my probs started at 26, but a friend of mine had same issue at age 34). No way to know what it is until you get tested, but I wanted to encourage you that it might not be something horrible.
I know that it's easier said than done, but try to just take it one day at a time; and know that no matter what, we'll be here for you.