I have that happen quite often. I tend to relate it to how long things have been in my colon - the longer (when in remission or close to it) it's been in there, the more water that's been removed, and the more it's been "compressed". I could be totally off base though!
Pan-colitis and GERD diagnosed May 2003
Osteopenia (hip and spine) diagnosed Feb 2006
Status: close to remission?!?!?
10mg Pred, Asacol 12 per day, Azathioprine 100mg, Aciphex, Forvia, and Pro-Bio
Remicade: 1st infusion 06/17/08: Next (3rd) infusion 08/12/08