Figure 10a. Occlusive adenocarcinoma. (a) Contrast-enhanced 2D coronal CT image with soft-tissue windowing shows an annular sigmoid mass (arrowheads). The endoscope could not be passed beyond the lesion to evaluate the proximal colon. (b) Endoluminal 3D view from CT colonography shows a synchronous 15-mm polyp on a fold in the ascending colon. Although the 2D views are better for evaluating the invasive primary tumor, 3D views remain valuable for detecting proximal synchronous lesions.