My gynecologist "guessed" at a fistula (she was right), and told me to go to my CR surgeon. She got me on antibiotics immediately, until I was able to get into the CR surgeon. The GI doc actually wanted nothing to do with a fistula. I do not go to him anymore. So, going by my experience, I'd recommend trying to get in to the surgeon asap.
S/he will probably do a scope, and may recommend further testing such as an MRI and/or EUA, depending on what s/he can see during the scope.
There are numerous procedures which your surgeon will detail for you - I've elected to forgo all procedures and therefore have a seton in my R/V fistula (since '12). A seton is not an unusual "first step" prior to any other attempts to fix the fistula.
As noted above, there are a fair number of us out here who have R/V fistulas - or other types of fistulas. A "search" should give you a fair amount of reading. In addition, I'm hoping more will chime in to this thread to give you further guidance.
Nancy