Clostridium difficile colitis, also known as pseudomembranous colitis, is a common cause of antibiotic-associated diarrhoea, and increasingly encountered in sick hospitalised patients. If undiagnosed and untreated, it continues to have high mortality. It may be classified as a form of infectious colitis.
C. difficile infection is usually preceded by antibiotic use or chemotherapy and is therefore usually encountered in unwell, hospitalised patients with significant comorbidity.
Typically, patients present with diarrhoea, fever, raised white cell count and abdominal pain with distension.
Clostridium difficile is a gram-positive anaerobe which is not a normal bowel commensal, but rather colonises the bowel after the normal colonic biology has been disrupted. This is typically due to antibiotic use or chemotherapy within 6 weeks of presentation 1. C. difficile produces two toxins (A and B) which have both cytotoxic and enterotoxic effects on the bowel. Clinical manifestation is thought to be predominantly due to toxin B 4.
An exudate composed of fibrin, white cells and cellular debris forms a pseudomembrane on the mucosa of the colon, which is characteristic 1. Definitive diagnosis is made by isolating C. difficile toxin in the stool sample.
Early in the disease, few findings may be evident on abdominal radiographs. Bowel dilatation, mural thickening and thumbprinting (due to thickening of the haustral folds) are seen later. Eventually, in untreated or fulminant cases, appearances will be those of toxic megacolon 3, with subsequent perforation and free intraperitoneal gas.
Barium studies demonstrate the same findings as plain radiography. Additionally, the pseudomembrane may be visible on double contrast studies. The role of barium enema has significantly reduced in the diagnosis of this entity due to the availability of CT and the risk of perforation 2.
Findings include 2:
- bowel wall thickening (most common)
- CT equivalent to thumbprinting
- accordion sign
- shaggy mucosal outline
- pericolic stranding: is present but minimal as it is mainly a mucosal disease
- peritoneal free fluid (ascites) is seen in up to 40% of cases 8
- although typically the whole colon is involved, the right colon and transverse colon may be affected in isolation in up to 5% of cases 2
- rectal involvement in the vast majority of cases (90-95%) 2
Treatment and prognosis
Treatment involves supportive therapy (fluid and electrolyte replacement) and eradication of C. difficile with antibiotics (usually vancomycin or metronidazole) 5.
A novel treatment option is that of faecal transplant, whereby 'healthy' faecal matter is either administered via nasogastric tube or directly into the colon, after having been donated by a family member 5.
Untreated pseudomembranous colitis carries a high mortality from toxic megacolon and perforation.
Other causes of toxic megacolon and colitis include:
- neutropenic colitis
- inflammatory bowel disease
- ischaemic colitis
- radiation induced colitis
- colonic lymphoma: also causes "thumbprinting"
If there is a history of bone marrow transplantation and the bowel involvement is not limited to the colon, then consider:
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- 8. Ramachandran I, Sinha R, Rodgers P. Pseudomembranous colitis revisited: spectrum of imaging findings. Clin Radiol. 2006;61 (7): 535-44. doi:10.1016/j.crad.2006.03.009 - Pubmed citation