Imaging Pearls ❯ Colon ❯ Pseudomembranous Colitis
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- Pseudomembranous colitis is caused by an overgrowth of the toxins-producing, Gram-positive Clostridium difficile bacteria, which results in copious diarrhea, fever, and abdominal pain. While antibiotic medication is the most common precipitating factor, the condition has also been associated with hypotensive episodes, chemotherapeutic drugs, and post-operative complications. Diagnostic imaging plays a critical role, especially in cases with nonspecific symptoms.
CT patterns of acute enterocolitis – a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra
Emergency Radiology (2025) 32:971–988 - A plain abdominal radiograph may reveal a dilated colon with the classic thumbprinting sign, indicative of submucosal edema and inflammation. Once pseudomembranous colitis is clinically suspected, radiographs serve a valuable role in serial monitoring to assess for progressive colonic dilatation and to identify complications such as perforation or toxic megacolon. CT provides a more detailed assessment, typically demonstrating diffuse or segmental colonic dilatation with edematous mural thickening. Pan colitis, is usual with this particular bacterial infection. Thickened haustral folds may be visualized, producing the characteristic thumbprinting sign , and in some cases, the accordion sign, reflecting trapped oral contrast between thickened haustral folds .
CT patterns of acute enterocolitis – a practical guide for the emergency radiologist
Snehal Rathi · Garima Suman · Avinash Nehra
Emergency Radiology (2025) 32:971–988
- Pseudomembranous Colitis
Clostridium difficile overgrowth
Often secondary to to antibiotic use
Most commonly involves entire colon (pancolitis)
- May be limited to right colon in up to 40%
CT findings:
- Significant wall thickening (can be > 3 cm), thicker than all other causes except Crohn’s disease
- Irregular or eccentric wall thickening
- Mural hypoattenuation (edema) or hyperattenuation (acute inflammation)
- Thumbprinting- thickened haustra due to edema
- “Accordian sign”- oral contrast between thickened haustra
- Pseudomembranous Colitis: CT Findings
- Marked wall thickening often concentric
- Accordian sign
- Stranding around bowel
- May be a pancolitis or segmental in nature
- Ascites not uncommon - Pseudomembranous Colitis: Accordian Sign
The accordion sign is seen when orally administered contrast material becomes trapped between markedly thickened haustral folds, giving the appearance of alternating bands of high attenuation (contrast material) and low attenuation (edematous haustra). The accordion sign is highly suggestive of PMC, although it is usually seen only in advanced cases. Its appearance may vary depending on the degree of edema of the haustral folds and the amount of contrast material trapped between the folds. With significant fold enlargement, barium that is deeply entrapped between markedly thickened folds may simulate intramural tracts. - “Pseudomembranous colitis (PMC) is an acute infectious colitis caused by toxins produced by an unopposed proliferation of Clostridium difficile bacteria in the colon . C difficile infection is responsible for virtually all cases of PMC and for up to 20% of cases of antibiotic-associated diarrhea without colitis. Over the past few decades, PMC has emerged as a significant medical problem, largely due to the increased use of prophylactic and broad-spectrum antibiotics.”
Pseudomembranous Colitis: Spectrum of Imaging Findings with Clinical and Pathologic Correlation
Kawamoto S, Horton KM, Fishman EK
July 1999 RadioGraphics, 19, 887-897 - “C difficile infection is nosocomial and can be epidemic or endemic in hospitals or nursing homes. PMC usually occurs as a complication of antibiotic therapy but is also associated with abdominal surgery, colonic obstruction, uremia, or prolonged hypotension or hypoperfusion of bowel. It also occurs with increased frequency in patients with severe debilitating disease such as lymphoma, leukemia, and advanced human immunodeficiency virus infection. PMC is a toxin-mediated disease that requires production of two toxins by the C difficile organisms for clinical expression. Toxin A is an enterotoxin, whereas toxin B is a cytotoxin .”
Pseudomembranous Colitis: Spectrum of Imaging Findings with Clinical and Pathologic Correlation
Kawamoto S, Horton KM, Fishman EK
July 1999 RadioGraphics, 19, 887-897
- "Although routine CT screening of antibiotic associated diarrhea is not advocated, the 88% positive predictive value of a diagnosis of C. difficile colitis in those who are scanned may merit consideration of treatment by clinicians on the basis of the CT results alone."
Evaluating the CT Diagnosis of Clostridium Difficile Colitis: Should CT Guide Therapy?
Kirkpatrick IDC et al.
AJR 2001;176:635-639