Amoebic colitis

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.

Clinical presentation

Amoebic colitis presents with abdominal pain and dysentery. Colonic manifestations comprise a spectrum of disease, including :

  • acute proctocolitis (dysentery)
  • perianal ulceration
  • fulminant colitis leading to colonic wall perforation
  • toxic megacolon
  • chronic (nondysenteric) colitis
  • ameboma

Radiographic features

  • 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
  • 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.


Differential diagnosis