 [ Symptoms ] does ibs lead to crohn is disease or ulcerative colitis [ Disease ] there is no evidence that irritable bowel syndrome ibs is a forerunner of inflammatory bowel disease crohn is disease and ulcerative colitis together referred to as ibd having said that there are interesting observations that suggest that some of the factors causing ibs and ibd may be similar involving the intestinal immune system and bacteria within the intestine the great differences between ibs and ibd makes it unlikely that they are caused by identical processes it is more likely that the manifestations they share    for example abdominal pain and diarrhea    are a function of the ability of the intestine to respond to disease causing processes no matter how different in a limited number of ways