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For further information, see CMDT Part 35-07: Amebiasis
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Essentials of Diagnosis
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Mild to moderate colitis with recurrent diarrhea
Severe colitis: bloody diarrhea, fever, and abdominal pain, with potential progression to hemorrhage or perforation
Hepatic abscess: fever, hepatomegaly, and abdominal pain
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General Considerations
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The Entamoeba complex contains three morphologically identical species
E dispar, which is avirulent
E moshkovskii, which is also avirulent
E histolytica, which may be an avirulent intestinal commensal or lead to serious disease
Humans are the only established host for E histolytica
Transmission occurs through ingestion of cysts from fecally contaminated food or water
Infection can be transmitted person-to-person
Flies and other arthropods also serve as mechanical vectors
Disease follows penetration of the intestinal wall, resulting in diarrhea, dysentery, and extraintestinal disease (see Amebic Liver Disease)
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E histolytica infections are present worldwide but are most prevalent in subtropical and tropical areas with crowded conditions, poor sanitation, and poor nutrition
Urban outbreaks have occurred because of common-source water contamination
Of 500 million persons worldwide infected with Entamoeba, most are infected with E dispar and an estimated 10% (50 million) are infected with E histolytica
Mortality from invasive E histolytica is about 100,000 per year
Severe disease is more common in
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Diarrhea may begin within a week of infection, although an incubation period of 2–4 weeks is more common
Onset of abdominal pain and diarrhea is gradual
Fever is uncommon
Periods of remission and recurrence may last days to weeks or longer
Abdominal examination may show
Distention
Tenderness
Hyperperistalsis
Hepatomegaly
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Includes colitis and dysentery, with worse diarrhea (10–20 stools per day) and the appearance of bloody stools
Physical findings of dysentery
Fulminant amebic colitis can progress to
Necrotizing colitis
Intestinal perforation
Mucosal sloughing
Severe hemorrhage
Localized granulomatous lesions (amebomas)
Can present after either dysentery or chronic intestinal infection
Clinical findings include pain, obstructive symptoms, and hemorrhage and may suggest intestinal carcinoma
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Differential Diagnosis
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Inflammatory bowel disease
Giardiasis, Shigella, Salmonella, Campylobacter
Irritable bowel syndrome
Lactase deficiency
Cryptosporidiosis, cyclosporiasis
Annular colonic carcinoma, tuberculosis, or lymphogranuloma venereum
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Diagnosis is typically made by identifying organisms in the stool
Molecular diagnosis is possible from multi-pathogen panels, which are sensitive and specific, but expensive
E ...