IBD. IBD is the term used to describe a group of idiopathic chronic inflammatory intestinal bowel diseases.Two main categories-Ulcerative colitisCrohn\'s disease(Indeterminate colitis). IBD. Pathogenesis is unknown.Many overlapping histological, endoscopic, radiological and clinical findings. But...clear differences in distribution and depth of inflammation in the bowel.Crohn\'s is transmural affecting any part of the GI tract.UC affects the colonic mucosa only..