Atypical hyperplastic polyps at double-contrast barium enema examination.

At radiography, hyperplastic polyps classically appear as smooth, sessile elevations less than 5 mm in diameter. However, a retrospective review of double-contrast barium enema studies in 22 patients with 31 pathologically proved hyperplastic polyps revealed an average polyp size of 7.3 mm, with a range of 3-21 mm. Fifteen polyps (48%) were 2-5 mm, 12 (39%) were 6-10 mm, and four (13%) were greater than 10 mm in diameter. Twenty-nine polyps (94%) were sessile, and two polyps (6%) were pedunculated. Twenty-three polyps (74%) had a smooth contour, and eight polyps (26%) were lobulated. Twenty-six of the hyperplastic polyps (84%) were located in the rectosigmoid colon. If the radiologic criteria for an atypical hyperplastic polyp at double-contrast barium enema examination include size greater than 5 mm, lobulation, and/or pedunculation, 16 of the 31 hyperplastic polyps (52%) could be classified as atypical. Thus, radiologists should be aware that many hyperplastic polyps seen at double-contrast barium enema examination do not fit the classic description of a smooth, sessile elevation less than 5 mm in size but instead appear as larger, more lobulated lesions that are indistinguishable from adenomatous polyps.