Amoebiasis pathophysiology

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Yazan Daaboul, M.D.; Serge Korjian M.D.

Transmission

• E. histolytica cyst is usually transmitted by the fecal-oral route through contaminated drinking water or food)
• E. histolytica cyst may also be transmitted indirectly through direct contact with infected individuals.

Pathogenesis

• Following transmission, E. histolytica trophozoites inhabit in the large intestine of the human host.
• In the large intestine, the trophozoite invades the intestinal mucosa into the blood stream. Simultaneously, they form resistant cysts that are then excreted in human stools.
• Once in the bloodstream, the trophozoite migrates into the portal circulation and develops amebic liver abscess.

Invasion of Intestinal Mucosa

• E. histolytica trophozoites secrete proteases, which induce the release of mucin from goblet cells, resulting in glandular hyperplasia.
• E. histolytica is

Pathology

Gross Pathology

On gross pathology, the following findings may be present in patients with amebiasis:

• Wavy surface epithelium (results from focal release of mucin and spasm of the muscular layer)
• Nodular and/or irregular ulcers in the cecum (most common), sigmoid colon, and rectum. Early ulcers are usually in the interglandular epithelium.

• Nodular: small (sub-centrimetric), rounded, elevated lesions with necrotic center and edematous rim
• Irregular: large (1-5 cm), shallow with broad elevated margins

Note: the mucosal folds may occasionally hide small colonic ulcers (false-negative results)

Microscopic Pathology

• On microscopic pathology, amebiasis is characterized by a flask ulcer (deep, microhemorrhagic ulceration involving the submucosa), which is a characteristic of advanced disease.
• Additional findings may be present in patients with amebiasis:

• Interglandular ulceration
• Hyperemia
• Thickened mucosa
• Reactive glandular hyperplasia
• Stromal edema
• Infiltration of neutrophils, eosinophils, and macrophages
• Lymphoid aggregates
• Detection of amebas on surface exudate
• Tissue necrosis, usually fibrinoid (advanced lesion)
• Formation of granulation tissue (advanced lesion)

Gallery

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  Invasive extraintestinal amebiasis. Adapted from Public Health Image Library (PHIL).

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  Amebic abscess of liver. Adapted from Public Health Image Library (PHIL).

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  Intestinal ulcers due to amebiasis. Adapted from Public Health Image Library (PHIL).

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  Intestinal ulcers due to amebiasis. Adapted from Public Health Image Library (PHIL).

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  Intestinal amebiasis. Adapted from Public Health Image Library (PHIL).

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  Amebic abscess in liver. Adapted from Public Health Image Library (PHIL).

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  Amebic abscess in liver. Adapted from Public Health Image Library (PHIL).

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  Amebiasis in intestine. Adapted from Public Health Image Library (PHIL).

References

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