Amoebic colitis is a type of infectious colitis, more common in tropical and subtropical areas. The causative agent is the trophozoite form of the protozoan Entamoeba histolytica. In most cases of transmission, the cyst form lives in the colon as a commensal and patients remain asymptomatic.
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Clinical presentation
Amoebic colitis presents with abdominal pain and dysentery. Colonic manifestations comprise a spectrum of disease, including 1,2:
- acute proctocolitis (dysentery)
- perianal ulceration
- fulminant colitis leading to colonic wall perforation
- toxic megacolon
- chronic (nondysenteric) colitis
- ameboma
Radiographic features
CT
- appearances of infectious colitis on CT are variable and nonspecific
- amoebic colitis may present with ulceration and skip lesions, mimicking Crohn disease
- collar button or aphthous ulcers
- ameboma: large lesions mimicking a tumor
- any part of the colon may be involved, but typically the cecum and rectum are more severely affected
- a coexisting liver abscess may be seen
- the ileum is spared; helps to differentiate it from Crohn or tuberculosis, which typically involve the terminal ileum
Treatment and prognosis
Antiparasitic therapy for amoebic colitis requires confirmation with laboratory investigation, including a fecal exam.
Complications
- bowel perforation
- extraintestinal disease, including amoebic liver abscess (most common), brain abscess, peritonitis, pleuropulmonary and/or genitourinary disease, and pericarditis 1
Differential diagnosis
- other infectious colitides (e.g. Yersinia, Clostridioides difficile)
- ileocecal tuberculosis
- ischemic colitis
- inflammatory bowel disease
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