Enhancing mass at the junction between descending colon and sigmoid colon (dotted blue line) results in proximal large bowel obstruction, with the caecum (yellow * ) most prominently distended.
The ileocaecal valve (orange arrow) is competent and there is no associated small bowel obstruction; the small bowel loop (green arrows) are collapsed.
Widespread gas is seen adherent to the bowel wall. It can be shown not to be intramural, as A) the gas is on the luminal side of the mucosa (red dotted line) and B) it is only visible where there is liquid faecal matter next to it: it is never seen anti-dependently. Also the fact that the bowel wall enhances normally (red arrows) is against the presence of ischaemic colitis, the most common cause of pneumatosis coli in this setting.