A, A vascular pattern, villous epithelium, and normal lymphoid nodularity are visible. B, A thin transparent glistening mucosa and delicate vascular network are visible. C, Terminal ileum in a child with Crohn disease (CD) shows mucosal thickening and erythema, complete loss of vascular pattern, pseudopolyps surrounded by deep ulceration, and luminal narrowing. D, Linear ulcer directly adjacent to normal colon mucosa in a young child with CD. E, Tissue in the stomach antrum of a 10-year-old child with CD. F, An adolescent with ulcerative colitis has diffuse erythema, loss of vascular pattern, and granular-appearing superficial ulceration.