Crohn's and IBS are 2 different diseases.
Crohn's is inflammation of the intestinal tract and occurs anywhere from the mouth to the anus, causing swelling and pain and often gives diarrohea.This can lead to the bowel becoming very inflamed and longer term may require operation.
IBS (irritable bowel syndrome)which gives abdominal pain, bloating and changes in bowel habit - sometimes constipation, sometimes diarrohea. IBS is usually treated by a combination of drugs and changes to diet and lifestyle.