The term “inflammatory” bowel disease” applies to idiopathic, chronic inflammatory bowel disease (IBD): Crohn’s disease and ulcerative colitis. They occur among all age groups but a peak incidence in the second and third decades.

Most of IBD occur as ulcerative colitis, but the incidence of Crohn’s disease has risen over the past 20 years.

These disorder are seen most commonly in Northern Europe and North America. IBD is rare in central America, South America, Africa, Middle East and Asia.

Most of IBD in Iran also occur as ulcerative colits, but Crohn’s disease is rare. There are no pathogonomonic clinical, endoscopic, or histologic features of the idiopathic IBD’s. Many gastrointestinal disorders may mimic the broad spectrum of feature in IBD. So it is particularly important to exclude other disorders, and much attention applies to rare disorders of gastrointestinal tract.