In any severe colonic inflammatory process (but most commonly ulcerative colitis), inflammatory polyps may form in the surviving islands of mucosa between the areas of ulceration. When the disease is quiescent, they are more accurately referred to as postinflammatory polyps. They may be focal, segmental or diffuse. The polyps may be sessile or filiform (worm-like), but it is rare for them to be pedunculated. The distinctive appearance of filiform polyps, also illustrated in Film .2, indicates their inflammatory etiology; adenomatous polyps do not have this shape. These residual polyps, which represent a healing response to the colonic inflammation, can usually be distinguished from acute inflammatory polyps in ulcerative colitis by the absence of any background granularity or ulceration. Film .3 and .3Z illustrate several inflammatory polyps (arrows) in the sigmoid colon in a patient with active ulcerative colitis, as evidenced by the diffusely granular and finely ulcerated mucosa. Postinflammatory polyps may be the only radiographic clue to the presence of inflammatory bowel disease. Occasionally, these polyps may become extremely large and mimic carcinoma.