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
- Escherichia coli
- Chlamydia trachomatis
- Clostridium difficile: Clostridium difficile colitis
- tuberculosis: tuberculous colitis
- amoebiasis: amoebic 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 the portion of the 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 the clinical situation, which includes colitis from other causes:
- 1. Thoeni RF, Cello JP. CT imaging of colitis. Radiology. 2006;240 (3): 623-38. Radiology (full text) - doi:10.1148/radiol.2403050818 - Pubmed citation
- 2. Jacobs JE, Birnbaum BA. CT of inflammatory disease of the colon. Semin. Ultrasound CT MR. 1995;16 (2): 91-101. Pubmed citation
- 3. Gore RM, Miller FH, Yaghmai V et-al. Inflammatory conditions of the colon. Semin Roentgenol. 2001;36 (2): 126-37. Pubmed citation
- 4. Horton KM, Corl FM, Fishman EK. CT evaluation of the colon: inflammatory disease. Radiographics. 2000;20 (2): 399-418. doi:10.1148/radiographics.20.2.g00mc15399 - Pubmed citation
- 5. Philpotts LE, Heiken JP, Westcott MA et-al. Colitis: use of CT findings in differential diagnosis. Radiology. 1994;190 (2): 445-9. doi:10.1148/radiology.190.2.8284397 - Pubmed citation
- 6. Radiology and imaging of the colon. Springer. ISBN:3540435972. Read it at Google Books - Find it at Amazon