It is the 312 area code on this page about the dietary study http://www.rush.edu/rumc/page-1144692715094.html so it is the downtown Chicago location, the actual Rush University Hospital. On Paulina Ave, wherever that is.
I wonder what kind of diet they want you to do for the study, if it's eating vegetable puree all the time, no thanks, too expensive. If it's eating expensive SCD products, no thanks, too expensive. Anything else, I'd be willing to try. I'm seriously thinking about calling them up to ask about it! It's only 1 visit a month, I could manage that.
BTW - the dietary and supplement study is not just UC, it is Crohn's too. The hypnotherapy one http://www.rush.edu/rumc/page-1193858476957.html does say UC only.