I have a perianal fistula, very simple one that doesn't involve my pouch.
I had an abscess drained, then cyclical pain... Filling, then bursting, over and over, so we confirmed fistula by MRI... So my surgeon placed a seton drain. It is a length of surgical rubber band, essentially, that goes through the anus, then through the fistula, then out the drainage "hole" near the anus. The ends get tied together, and it then forms a loop. It can be very tight, a "cutting" seton, that "cuts through" the tissue, forming scar tissue behind it to heal the tract, or a "draining" seton, which hangs loose, allows the inflammation to chill, and lets the fistula drain without the fill/burst cycle. Kinda think of an anal "piercing" with a rubber band, and you'll get the picture. I have a draining seton. My surgeon doesn't want to mess with cutting my sphincters, because we already took a hit there... Doesn't want to risk incontinence (nor do I, as I'm totally continent and without leakage issues).
It doesn't cure you of your fistula (a draining seton), but it made life livable again.
Down the road, might have something done, but for now, I just live with it. It's barely noticeable to me these days, have had it for coming on 5 months). I wear a 2X2 gauze pad near it as it puts out a wee bit of mucus, I take an occasional sitz bath, but mostly do nothing extraordinary these days. Went to Puerto Rico, in the rainforest, bio bay, ocean... No issues. I work as a critical care nurse, and it currently doesn't affect me at all. Again, I rarely feel it. Wiping needs to be a little more gentle, use a Tuck's or baby wipe at times, since it could break if I was too rough, but it's pretty sturdy overall.
PM me if you have more in depth questions.