Inaccuracy of radiographic measurements of colon polyps.

Polyp size is one of the main determinants of the surgical management of polyps in areas without colonoscopy services. We reviewed 47 patients with 59 polyps at two hospitals. Polyp dimensions were measured directly from air contrast barium enema radiographs, and again after resection and fixation. In over 95% of polyps the radiographic size exceeded the pathologic size by 10 to 100%. Since surgery may be decided on the basis of polyp size, an inaccurate measurement may result in unnecessary colonoscopy or laparotomy. We therefore recommend a correction factor derived from measuring a rectal tube of known diameter.