The accordion sign (also known as concertina sign) is seen on CT examinations of the abdomen and refers to the similarity between the thickened edematous wall of pseudomembranous colitis and the folds of an accordion. This appearance is the result of hyperemic enhancing mucosa stretched over markedly thickened submucosal folds and is also seen when contrast is trapped between edematous haustral folds and pseudomembranes formed on the luminal surface of the colon 2.
Although it has been reported to be a specific sign of severe Clostridioides difficile colitis, it has also been described in other forms of non-specific, ischemic, and non-Clostridioides difficile infective colitides 1.
- 1. Fishman EK, Kavuru M, Jones B et-al. Pseudomembranous colitis: CT evaluation of 26 cases. Radiology. 1991;180 (1): 57-60. Radiology (abstract) - Pubmed citation
- 2. Macari M, Balthazar EJ, Megibow AJ. The accordion sign at CT: a nonspecific finding in patients with colonic edema. Radiology. 1999;211 (3): 743-6. Radiology (full text) - Pubmed citation