Hi there,
I had a fistula that they said was blind ended. It went off my colon and off to no where. The only reason I found out I had one, was eventually an abscess formed at the end and filled with infection, which when it filled up would travel back up the fistula tract and into the rectum and out my anus (sorry for the TMI). Thats is how I found out I had one and was referred for and MRI to get the exact location to make it easier for the surgeon. I may have noticed it sooner but I have per anal crohns that has cause numerous fissures and some skin tags so the discomfort I was feeling I attributed to that.
I am not sure if there is a for sure way to tell but and MRI, if anything, can for sure determine if you have one.
Hope this helps..