Gastrointestinal Imaging

Diverticulum, sigmoid, giant

large diverticulum (sizes between 6 and 27 cm have been reported) originating in the sigmoid colon, mostly in elderly persons. It is considered as a rare complication of diverticulosis because the wall contains no muscularis mucosae. The pathogenesis is probably based on a submucosal covered perforation of a diverticulum. Air may enter the diverticulum during episodes of elevated intraluminal pressure in the colon, for instance during defaecation, and may remain trapped in the diverticulum leading to its progressive enlargement and final large size at the time of diagnosis. The normal mucosa becomes gradually replaced by inflammatory granulation tissue. At clinical examination a mass may be palpable in the left lower abdomen. The diagnosis is based on the plain radiograph of the abdomen showing a large air-filled structure.

Plain radiographs show a large, round, or elliptical radiolucency, with thin, smooth margins measuring between 5 and 30 cm. An air fluid level is seen in some patients. On rare occasions the diverticulum is lined by linear calcifications, probably due to long standing inflammation. Contrast enema will reveal contrast filling of the abnormal structure in the majority of patients. Normally the margins are smooth. If irregular or lobulated margins are present, inflammation or carcinoma may be suspected. In addition, diverticulosis of the proximal colon will be seen in 50% of cases of giant diverticulum of the sigmoid colon.

CT (Fig.1) will show a voluminous gas-filled cavity close to the sigmoid, which may contain contrast material confirming communication with the colon lumen.

ALB

To view high resolution images,
please register first.

Click  here to register.

Already registered? Enter your e-mail in the window below.
Re-register

Fig.1

CT of the pelvis following rectal contrast medium administration. A very large spherical cavity is filled with air and contains contrast medium in its dependent portion. The cavity communicates (arrow) with the sigmoid. Note also thickened wall of sigmoid and the presence of small sigmoid diverticula.
Diverticulum, sigmoid, giant, Fig.1