Pseudomembranous Colitis: Spectrum of Imaging Findings with Clinical and Pathologic Correlation

Abstract

Pseudomembranous colitis (PMC) is a potentially life-threatening acute infectious colitis caused by one or more toxins produced by an unopposed proliferation of Clostridium difficile bacteria. PMC is characterized by the presence of elevated, yellow-white plaques forming pseudomembranes on the colonic mucosa. These plaques can be visualized at both pathologic analysis and endoscopy. Plain radiography, contrast enema studies, and computed tomography (CT) are useful in the evaluation of PMC. Plain radiography of the abdomen can demonstrate polypoid mucosal thickening, "thumbprinting" (wide transverse bands associated with haustral fold thickening), or gaseous distention of the colon. A toxic megacolon with distention and occasionally pneumoperitoneum may be seen in the most severe cases of PMC involving perforation. At contrast enema studies, the primary finding in mild cases of PMC is small nodular filling defects representing the mucosal plaques. With more extensive colonic involvement, the plaques are larger and coalesce to form an irregular bowel wall margin. Mural thickening and wide haustral folds caused by intramural edema may also be seen. A contrast enema study is contraindicated in patients with severe PMC due to the danger of perforation. Common CT findings include wall thickening, low-attenuation mural thickening corresponding to mucosal and submucosal edema, the "accordion sign," the "target sign" ("double halo sign"), pericolonic stranding, and ascites. Familiarity with these imaging characteristics may allow early diagnosis and treatment and prevent progression to more serious pathologic conditions.

Toxic megacolon associatedClostridium difficilecolitis

“…They reported a 24% mortality rate for subtotal colec tomy compared to 40% for sigmoid resection alone. In a study by Koss et al [25] , total colectomy resulted in a lower mortality rate (11%) compared to those with a left hemicolectomy (100%).…”

“…An endoscopy may be dangerous, especially in a setting of fulminant colitis due to the increased risk of perforation [6,25] . A study by Johal et al [26] , however encouraged the use of flexible sigmoidoscopy as a tool for the diagnosis of C. difficile toxic colitis when stool assays are negative.…”

Clostridia Difficile Diarrhea

“…Though its usually unnecessary, direct visualization of colitis by endoscopy is virtually diagnostic as they are few other infections that would cause pseudomembrane formation. 25 Endoscopy carries the risk of perforation in fulminant colitis.…”

Multidetector computed tomography of acute abdomen

“…In patients on potent oral antibiotics, the normal bacterial flora of the colon is disrupted, resulting in the overgrowth of Clostridium difficile and causing pseudomembranous colitis. Although non-specific, CT findings include mural thickening, with a halo or target pattern caused by submucosal oedema, peri-colic inflammatory changes, and ascites [37,38] (Fig. 6).…”

“…Since pseudomembranous colitis predominantly affects the mucosa and submucosa, peri-colic stranding is often disproportionately mild relative to the colonic wall thickening [36]. Sometimes, contrast material is caught between thickened haustra, producing an accordion-like appearance [37], which is suggestive of pseudomembranous colitis but typically only occurs in severe cases [36].…”