Figure 2b. Segmental colonic spasm in the descending colon in a 65-year-old man with symptoms of colorectal cancer. (a) Three-dimensional endoluminal CT image shows an irregular, circular narrowing of the colonic lumen (arrow), a finding that simulates a stenosis. (b) Supine coronal contrast-enhanced CT scan shows focal, irregular circular wall thickening with shoulder formation (arrow). The apparent lesion demonstrates enhancement. (c) Prone coronal CT scan shows a normal smooth colonic wall without signs of stenosis or wall thickening (arrow), findings that indicate that the spasm has relaxed.