Colonic perforation, like gastroduodenal perforation, can appear as massive pneumoperitoneum with free gas throughout the abdomen and pelvis. If free gas is present only in the pelvis, the colon, and not small bowel, is the usual site of perforation. The reverse is true for suprameso-colic free gas. However, exceptions occur, as sigmoid perforations may have free gas only in the supramesocolic compartment, in which case focal signs such as wall thickening and peri-colonic stranding may be the only signs pointing towards the site of perforation (Fig. 11). Other CT findings observed in colonic perforation are of a complex mass, inflammatory change, an extraluminal fluid collection, and bowel wall thickening around the perforation site.2,33 Occasionally, a sigmoid diverticulum can perforate into the mesosigmoid, with gas tracking into the retroperitoneum. Free retroperitoneal gas, often in the anterior pararenal space, may also be caused by colonoscopic perforations of the posterior walls of the sigmoid, ascending and descending colon. Presentation is delayed unlike in intraperitoneal colonoscopic perforations where there is massive pneumoperitoneum due to procedural gas insufflation. These iatrogenic perforations occur in approximately 1 in 1000 patients. The rate of occurrence of symptomatic luminal perforation in CT colonography is four times lower than for colonoscopy.34
Learn about over 1,000 camps and ghettos in Volumes I-III of this encyclopedia, which are available as a free PDF download. This reference provides text, photographs, charts, maps, and extensive indexes.
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