Clinical History
A 34 year old male patient was presented to our institute with recent symptoms of diarrhoea, vomit, fever and abdominal pain, unresponsive to common antibiotic therapy.
Imaging Findings
The patient was affected by spastic tetraparesis for which a pulmonary respiratory support and an artificial feeding were needed. In last days a severe respiratory infection by staphylococcus aureus made it necessary to administrate large spectrum antibiotic therapy. After a week, intense abdominal pain with irrepressible diarrhoea, fever and vomit presented. For these symptoms a CT evaluation was requested. CT examination was made with single detector row equipment, before and after intravenous injection of iodinated contrast medium. The axial scans showed diffuse and circumferential wall thickening of all the colic tracts, from cecum to rectum, with a pericolonic stranding and ascites. In all tracts the “target sign” and the “accordion sign” were present, suggesting the diagnosis of pseudomembranous colitis. An endoscopic examination showed the presence of multiple yellow-green plaques forming pseudomembranes on the colonic mucosa completely and circumferentially involving the visualized segments of the colon, so confirming the diagnosis, and a bacteriological examination of the stool demonstrated the presence of Clostridium difficile cytotoxin.
Discussion
Pseudomembranous colitis is a severe acute infectious colitis caused by one or more toxins produced by an unopposed proliferation of Clostridium difficile bacteria. It usually occurs as a complication of antibiotic therapy but is also associated with abdominal surgery, colonic obstruction, uraemia, or prolonged hypotension or hypoperfusion of bowel and it is characterized by the presence of multiple yellow-white plaques forming pseudomembranes on the colonic mucosa [1]. Many CT findings have been described to be associated to this disease, even if with different degrees of specificity. The accordion sign was originally defined as the presence of alternating oedematous haustral folds separated by transverse mucosal ridges filled with oral contrast material, simulating the appearance of an accordion. This CT finding has been reported to be a specific sign of severe Clostridium difficile-related colitis, but some Authors reported that even other forms of nonspecific or ischemic colitis or some types of colitis caused by other bacterial species, may show this sign [2]. In cases of Clostridium difficile-related colitis, the high-attenuating oral contrast material is trapped between the thickened oedematous folds and pseudomembranes in the colonic mucosa. However in some cases, as our case, the enhancing mucosa is stretched around markedly thickened submucosal folds, simulating the accordion sign even though oral contrast material is not present.
The target sign (also called double halo sign) is often seen in Clostridium difficile-related colitis. It consists of two or three concentric rings of different attenuation, indicating mucosal hyperemia and submucosal oedema or inflammation, reflecting the different layers enhancement [3]. The rings of varying attenuation are better appreciated during the arterial phase.
Pseudomembranous colitis may present as a pancolitis or segmental colitis, even if CT scans show an abnormal bowel wall thickening most commonly involving the entire colon [4]. The association of a diffuse accordion sign in a pancolitis pattern, in a patient with a recent story of large spectrum antibiotherapy, are highly suggestive of pseudomembranous colitis.
Differential Diagnosis List
Pseudomembranous pancolitis
Final Diagnosis
Pseudomembranous pancolitis
