Jack, I'm not a doctor, so you should follow solid medical advice. But I know there are good ER doctors and bad ones. One of my friends is a good ER doctor, and I've heard some stories.
Here's a link to one of the sites that say cranberry products can be risky for kidney stones:
http://www.newhope.com/nutritionsciencenews/NSN_backs/Jun_01/news4.cfm?path=print
If you don't have a problem with oxalates, maybe you'll be fine.
For me in my 20s, it was tea, for sure. I had two minor kidney stone episodes, and then the big one that landed me in the hospital. After the stones were analyzed, I stopped tea, and had no problems till now, a run of many, many years.
Good luck with your urologist!
Chris