Giant sigmoid diverticulum

                Gastrointestinal tract images Giant Diverticula, Giant colonic diverticula are sufficiently rare that individual reports are still being published. Most occur in the sigmoid colon. Their etiology is unknown, although several theories are postulated: First, a check-valve mechanism in the diverticular neck allows colonic content to enter but not exit.Or, a localized diverticular infection results in an abscess that eventually communicates with colonic lumen. Although less likely, such a cavity may also represent sequelae of a communicating duplication cyst. In either case, some of these cavities enlarge to giant proportions.
               Histologically, these giant diverticula do not have a mucosal lining, with the wall consisting mostly of fibrotic tissue, thus suggesting a contained perforation as their etiology. Patients range from asymptomatic to those presenting with bleeding or an acute abdomen. An occasional giant colonic diverticulum perforates and results in a pneumoperitoneum. Other rare complications include an associated carcinoma, small bowel obstruction, or even volvulus.
              These uncommon lesions can be suspected with conventional radiography and are diagnostic with a barium enema when barium flows into the diverticulum, thus establishing its colonic communication. Imaging shows a large gas collection, usually close to the sigmoid colon. The diverticular wall tends to be thin and smooth. Horizontal x-ray beam radiographs often reveal a gas-fluid level. The diverticular wall shows no CT contrast enhancement,
except if surrounding inflammation is present. Some rare chronic diverticula contain calcifications within their wall.
                 A thick-walled cavity or any nodularity should suggest a necrotic tumor rather than a giant diverticulum. A communicating duplication is rare in the sigmoid, usually is on the mesenteric side, is seen in a younger patient population, and histology should reveal an epithelial lining containing all layers of the colonic wall. Most giant colonic diverticula are resected.
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This is radiology images of giant sigmoid diverticulum. A: A conventional radiograph identifies a large gas-filled structure (arrows). B: A barium enema confirms a diverticulum (arrows) and establishes its communication with colon.
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