Is it possible to develop a perianal fistula or abscess on other side?

I don't know for sure but probably yes, I had a recto-vaginal fistula that had a couple of "branches" off of it which I didn't even know could happen so chances are anythings possible with those nasty things....this nasty disease!!

Best of luck on your surgery I hope all goes well and you become fistula free!! Keep us posted!

I've heard of them branching out all over the place. I remember when I had mine I was worried it was going to be like that on the inside when they went in to do surgery. My surgeon said they can become quite complicated. Of course we can also get multiple ones, so I would think it's entirely possible to get one on the opposite side. Right on the edge we can also get fissures though. So maybe it's just a cut that might be a bit swollen? Those can be very painful. I had a fissure next to my fistula opening and they repaired both in the same surgery. This was before I was diagnosed with Crohn's (but obviously already had it).