There is a large amount of free gas located with in the pelvis and retroperitoneal spaces. This appears to be arising from a perforation of the mid sigmoid colon.
At this point, the sigmoid colon lumen appears significantly narrowed. Contrast is present throughout the large bowel, extending into the rectum.
There is no obvious point of contrast extravasation from the bowel lumen. No free intraperitoneal fluid. The presence of pelvic fluid is difficult to identify due to streak artefact from the hip replacements.