With IBS you don't need an anatomical problem like the colon going through a hernia and being strangulated to cause severe pain. The nerves sensing the colon when they go off can cause severe pain all by themselves without a "good reason". That is part of what makes IBS so frustrating. It is like any other condition where the pain is from messed up nerves. You can't really do much until the nerve decides to stop sending severe pain signals.A spasm might be the reason, but the colon's nerves can send severe pain over normal stimuli, it doesn't have to be something abnormal.If this pain is new to you and started long after you were diagnosed with IBS it may be worth getting it checked out (as something new can happen) but most of the time it ends up being the IBS just being wonky. If it was going on when you were diagnosed then I would be less likely to get it checked out as it was going on when any tests were run.