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Signs
G. O’Sullivan, MD

in Imaging

Susan

The

Accordion

Sign1

a. Accordion contrast

b.
sign material in a patient (arrows) with pseudomembranous in crevices between the colitis folds. (PMC). (a, b) Contiguous CT sections show marked wall thickening of the colon with

APPEARANCE The accordion sign is a finding that may be seen on computed tomognaphic (CT) scans in patients who have received oral contrast material. It comprises alternating bands of lower soft-tissue attenuation and higher contrast material attenuation within the large bowel (Figure).

EXPLANATION The sign lower soft-tissue attenuation represents marked thickening component of the accordion of the haustral folds due

to

transmural edema. Small amounts of oral contrast material may become trapped within the crevices between these thickened haustnal folds. The bands of alternating lower and higher attenuation have been likened to the appearance of an accordion (1). This appearance may be variable depending on the degree of edema of the haustral folds and the amount of contrast matenial trapped between the folds.

Index

terms:

Colitis, Colon,

pseudomembranous,
CT, 75.12119

75.263

DISCUSSION The accordion sign has been described as a finding indicative of PMC (1). PMC is most commonly associated with antibiotic use, although other causes have been described (2). As antibiotic use has become more widespread, the prevalence of PMC has increased (2). The nonspecific symptoms of abdominal pain, fever, and diarrhea often create a diagnostic dilemma for the clinician. The radiologist’s mole has become more crucial as the use of CT for evaluation of intnaabdominal processes has increased. Knowledge of the associated clinical findings as well as the CT findings of PMC allow the radiologist to confidently suggest this diagnosis. The pathogenesis of PMC involves the overgrowth of

Radiology Abbreviation: PMC
=

1998;

206:177-178

pseudomembranous

colitis Virginia, Hospital, 5, 1997; accepted

1 From the Department of Radiology, Medical College of Virginia Commonwealth University, 401 N 1 2th St, Main 3rd Fl, Richmond, VA 23298-061 5. Received September revision requested September 29; revision received and October 7. Address reprint requests to the author.

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Clostridium difficile in response to a decrease in normal intestinal flora that results from antibiotic use. This organism produces toxins that cause direct mucosal damage. The characteristic pathologic findings include discrete, small yellow plaques (pseudomembnanes) that are adherent to the mucosal surface of a variable length of colon (2). Less frequent, the small bowel may be involved. The pseudomembrane consists of a layer of epithelial debris, fibnin, and polymorphonuclear leukocytes held in columns by strands of mucus (2). The pseudomembranous plaques cannot be seen radiologically. As the disease progresses, reactive edema develops in the lamina propnia, the submucosa, and eventually the subsenosa, leading to transmural thickening. It is this process that leads to the radiologic findings. Conventional radiographic findings are nonspecific but may include haustral thickening, colonic dilatation, and ascites. CT has become a frequently used imaging modality in patients with the nonspecific symptoms of undiagnosed progressing PMC and has yielded consistent findings in these patients. These findings include marked mural thickening, nodularity of the largebowel wall, and the accordion sign (alternating bands of edematous haustral folds separated by intraluminal contrast material)(1-3). Although the CT findings of mural thickening and nodulanity have been described in other colitides, the degree needed to account for the accordion sign is relatively unique to PMC. In

1991, Fishman and colleagues (1) noted its presence 26 patients with confirmed PMC. The sign has been ported to occur both in 51%-70% of patients with PMC and as a finding specific for PMC (2).

in five of further readvanced

PMC is confirmed by the presence of toxins in stool assays and supported endoscopically by direct visualization of the pseudomembranous plaques. If the diagnosis is not suspected, these tests are often not obtained early. Furthermore, stool assays may take 48 hours for diagnosis, and the results of sigmoidoscopy may be negative on nonspecific. Therefore, the radiologic findings may be the first suggestion of this process (3). Although PMC is treatable, it may become a life-threatening disease if not diagnosed in a timely fashion. Knowledge of the clinical and imaging findings of PMC, including the accordion sign, will assist in the diagnosis of this entity.

References 1. 2. 3. Fishman EK, Kavuru M, iones B, et al. Pseudomembranous colitis: CT evaluation of 26 cases. Radiology 1991; 180:57-60. Ros PR, Buetow PC, Pantograg-Brown L, Forsmark CE, Sobin LH. Pseudomembranous colitis. Radiology 1 996; 198:1-9. Boland GW, Lee MJ, Cats AM, Gaa JA, Saini S, Mueller PR. Antibioticinduced diarrhea: specificity of abdominal CT for the diagnosis of Clostridiurn difficile disease. Radiology 1994; 191:103-106.

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