Figure 17a. Large pedunculated polyp. (a) Axial CT image shows a pedunculated polyp (arrow) in the sigmoid colon. With the stalk, it measures 37 mm. However, such a polyp should be measured according to the size of the head, which is 13 mm. (b, c) Images from conventional (b) and virtual (c) colonoscopy show the head of the polyp (arrow). Histologic analysis revealed a hyperplastic polyp.