I've never heard of having a tube to hold the colon in place, but when I saw that you are going to have a fistulagram, I might be able to give some insight into what a fistula is and why you have the tube.
When I still had my colon, I had Crohn's and a fistula (a tunnel) that went from my colon to my right butt cheek. It caused an abscess, and a surgeon had to surgically cut it
open. She put a tube in the site to allow it to drain. That tube was so painful, because the skin around it was extremely tender.
I continued to work as a receptionist (mainly for the health benefits), which meant I had to sit at a desk all day. I sat on a donut and had to take a pain pill, just to get through the day. It was awful. The tube wasn't removed until I had my colon and rectum removed.
I remember doing warm sitz baths to soothe the tender skin around the tube and applying an antibiotic ointment that the doctor prescribed. Maybe your doctor can prescribe some of that ointment for you.
The tube is to prevent you from having all of that stuff be inside of you, so there is a benefit to it. I hope you pass the fistulagram and can have it removed soon.
Dx'd Crohn's in '99 at 28. Proctocolectomy and ileostomy in '06.
Disease-free, medicine-free, and very thankful to be healthy again :)