Fistula - unbearable pressure

My daughter has perianal fistula and just had a draining seton put in. She is experiencing terrible pressure that would build up making her double over and grip anything in sight and bear her teeth. Then,as she feels the fistula drain, pressure is lifted. She had this before the seton placement and was told this would stop after seton. Unfortunately, it's worth. Has anyone experienced this??
Thanks

She was on remicade until recently. Last blood test showed she's built anti-body which explains why the abscess and fistula. GI will be putting her on Humera and 6mp once her fever comes down. 10 days after Seton procedure, she's still having the awful pressure just before fistula drains and low grade fever. Any input from all of you will be really appreciated.

According to the surgeon, this is normal. That's why I'm posting here in hopes that someone can tell me if they had any experiences like it.

Is there anyone that can describe to me their fistula pain?????