Finding-the-Path: CT of the abdomen and pelvis
Computed tomography
Axial tomograms from a pelvic CT after oral contrast and without intravenous contrast show thickening of the wall of the sigmoid colon with inflammatory changes in the surrounding mesenteric fat (arrow) The inflammatory process abuts the superior and posterior aspects of the urinary bladder. Stool, oral contrast and gas are visible within the bladder (arrow). There is also a small amount of extraluminal air (arrow). Numerous sigmoid diverticula are present.
This constellation of findings is consistent with sigmoid diverticulitis complicated by a colovesicle fistula. A colonic carcinoma or lymphoma are much less likely possibilities.
Discussion
Diverticular disease exists in 6-8% of the population and its frequency increases with advancing age. Approximately one fourth of patients with diverticular disease develop at least one episode of diverticulitis. Diverticulitis results from micro or macroperforation of a diverticulum leading to an acute inflammatory reaction in the pericolic tissues. The inflammatory process may appear as an abscess, sinus tract or fistula, and less commonly as local or generalized peritonitis.
In elderly patients who present with fever and left lower quadrant pain, the diagnosis is straightforward and a barium enema may be the most cost-effective study to confirm the diagnosis. However, barium enema has a relatively low sensitivity (75-80%) in diagnosing diverticulitis. The poor sensitivity is due to the pericolic rather than luminal localization of the disease process. Computed tomography is superior to barium enema in detection of pericolic inflammation because of its ability to visualize the bowel lumen, the wall of the bowel and the pericolic fat.
The primary CT findings in uncomplicated diverticulitis include thickening of the wall of the involved segment of colon with infiltration of adjacent mesenteric fat and visualization of colonic diverticula. CT is especially useful in diagnosing complications of diverticulitis such as pericolic abscess, free perforation, colovesicle fistula or ureteral obstruction. In patients with a localized pericolic abscess, CT-guided percutaneous drainage may allow single stage surgical resection of the involved segment with primary anastomosis.
The differential diagnosis of acute diverticulitis on CT includes those disease processes that thicken the bowel wall and result in infiltration of mesenteric fat. These entities include a perforated colonic carcinoma, foreign body perforation, appendicitis and inflammatory bowel disease.
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Computed tomography
