I normally post on the MS site, but my dx is in limbo again, leaning towards lupus. I have been reading this site for a few weeks.
Anyway, part of my dx has been a kidney biopsy. While I was scared going in, it really was nothing. They do a CAT scan to see where the kidney is, numb the spot, give you something that makes you so relaxed you don't remember a thing. Then they keep you on your back for awhile, send you home to rest on your back for the day. I wasn't really sore or anything. The only problem I had was a moved 3 days later and I lifted boxes I shouldn't have, and that made me a little sore. They told me some people pass blood when urinating after the procedure, I didn't even do that. It really was a simple procedure, easier than the lumbar puncture I did.
As for the rheumy, don't hold back any info, tell him/her the symptoms, meds and any other pertinent info. I keep a small notebook of symptoms between visits and summarize it for the doc. It saves time if they just read it over, and I don't forget anything.
Good luck. Let us know how the appt goes.