I've had a rough time with rowasa (generic, which might make a difference), too. I've been waiting to give them a shot once again, but last time I used them, I could barely hold them for 10 minutes. Cramps, gas, urgency, etc.
I get left sided pain around the waist and a little below that I'm sure is UC related.
Aren't kidneys and the pain from infection more above the waist? I've never had one that I know of so I'm not sure.