How can you tell the difference between ibs and something more serious?

Rome 3 ; testing: Ibs is a diagnosis of exclusion. Rome 3 criteria helps. For example, mucus (a colon lubricant) when present in large volume may signal not only problems with colon spasm (ie. Irritable bowel syndrome), but also partial obstruction, infection, ; even sloughed colon lining. Testing distinguishes ibs from inflammatory bowel diseases (crohn's, ulcerative colitis), infection, ischemic gut. See doctor.