I had one that manifested itself as a recurring “cyst” for years (between 5 different doctors) until I did research and suggested it was a fistula.

I finally got to a doctor who would listen, but it took years to figure out why I would suddenly get a cyst that would grow very quickly and was so painful the last time that I begged to be put under (and that doctor downplayed my pain so I ran and never went back to that idiot).

TMI warning:

Turns out it wrapped around the rectal muscle; I had two surgeries and probably need a third if it’s even possible for them to give me back full control of the rectal muscle. So I have had to accept that sometimes I’ll uncontrollably lose a fart. At this point though, who of us can really trust it’s a fart anyway?