Hi...another IBS sufferer here and I have this pain what I think you may be describing. It is very difficult to describe but here goes. It is inside my back passage and feels like something is stuck there but what it actually is ...is a spasm..causing the muscles inside the back passage to slightly twist..causing a pain that I liken to "as though a hard object is stuck there, or I am being squeezed from the inside...or nipped from the inside"....hope this makes sense cause it is really hard to describe. I have had all the checks done for my IBS....sigmoidoscopy, colonoscopy etc etc..many times. My consultant was not in the least bit concerned when I told him of this pain...he told me the name..(cant member but very long)..My sister gets it too and sometimes it can be just an annoying niggly pain and at other times it can be excrutiating...I usually sit on a hot water bottle and take pain killers until it passes....I have piles inside and think this may be the trigger..not sure. Hope this helps..and if it is not the same as your pain ckirby25 sorry for the long post but may help some one else. Good luck tomorrow..and try not to worry......