Infectious colitis refers to inflammation of the colon due to an infective cause, including bacterial, viral, fungal or parasitic infections.
In Western countries, bacterial infection is the most common cause, while in developing countries parasitic infection is much more common. Men and women are affected equally by infectious colitis and the disease can occur in all ages with incidence increasing with age.
Infectious colitis can result from a wide-range of protean aetiological agents:
- Shigella sp
- Salmonella sp
- E. coli
- Chlamydia trachomatis
- Clostridium difficile: Clostridium difficile colitis
Imaging features are often not definitive for a particular organism.
Findings on ultrasound include increased symmetrical wall thickening and submucosal echogenicity. On colour Doppler, there may be increased mural flow.
If imaging is required, CT is usually the examination of choice.
Patients with infectious colitis from any cause typically have wall thickening (this usually demonstrates homogeneous enhancement). Low attenuation regions representing oedema may be detected within the wall. Other ancillary findings include:
- inflammation of the pericolonic fat
- multiple air-fluid levels due to increased fluid and fluid faeces
While there can be considerable overlap, the affecting segment of portion of colon however may be useful in suggesting a specific organism:
- usually limited to the right colon: Shigella, Salmonella
- diffuse involvement also occurs: cytomegalovirus, E. coli
- rectosigmoid: gonorrhoea, herpesvirus, and C trachomatis (lymphogranuloma venereum)
- involvement is usually confined to the descending and sigmoid colon: schistosomiasis - thought to be due to adult worms having a tendency to enter the inferior mesenteric vein
On imaging consider other forms of colitis dependent on clinical situation, which includes colitis from other causes:
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