I am new on here but not new to the issue of abcesses in that area!
Yes, for me scar tissue, not Crohns inflammation(to start with) will cause that kind of pressure in my rectum.
Especially if I have had more gas than usual and/or trips to the bathroom. I also have external skin tags (ya like hemmies) that just add to the pressure and pain. Sometimes after all the sits baths and heated packs, I just cave and stay off my feet til the swelling goes down.
I too am on Remicade and it does help, most of the time. Good luck with your test and I hope there is a simple answer for ya!