Irritable Bowel Syndrome (or IBS) is a chronic disorder of bowel function. IBS can lead to alternating episodes of constipation or diarrhea. It can cause abdominal pain and bloating that comes and goes with time. There are different types of IBS including IBS with constipation, IBS with diarrhea, or IBS with mixed symptoms (which means you may have both constipation and diarrhea).