I just want to say there are options and it is definately not a forever thing.
Women get fistulas all the time from being pregant and giving birth, it is definately not only with crohns.
So possible 90% of crohns patients get fistulas, but there is no way that 90 % of fistulas are from crohns.
They are very common and there is a mulitude of reasons for fistulas.
Guy66 is right on with this treatment can cause alot of trama for that delicate skin to handle, so that is why I said go see a doc.
They can determind what the best course of treatment. Minor surgery to antibodics are used to treat it. Some just do heal up on their own. But cancer and it's treatments are hard on the GI tract in general, so it is a good idea to check with a GI doc.
I am not a patient person, and so I used antibodics because I did not want to run the risk of infection. Plus running the risk of infection when you have cancer is a bad idea.