Liver & intrahepatic bile ducts

Infectious nonviral

Entamoeba histolytica abscess

Last author update: 1 May 2012
Last staff update: 21 July 2022

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PubMed Search: Entamoeba histolytica liver abscess

Komal Arora, M.D.
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Cite this page: Arora K. Entamoeba histolytica abscess. website. Accessed September 30th, 2023.
Definition / general
  • Also called amebic abscess; more common than pyogenic abscess worldwide but not in US (Med Clin North Am 1989;73:847)
  • Common in developing world (Exp Parasitol 2010;126:366)
  • Usually fecal oral spread; may also be sexually transmitted (Clin Infect Dis 2009;49:346)
  • Complication of 3 - 9% of amebiasis cases
  • Trophozoite:
    • Active stage that exists only in host and in fresh loose feces; 10 - 60 microns with small, single, round nucleus with distinctive karyosome
    • Thick, beaded nuclear membrane
    • Bubbly cytoplasm with ingested red blood cells
  • Complications: bacterial superinfection, extension or perforation into other structures; death in < 1% of cases
  • Diagnosis: serology is 90% sensitive
Diagrams / tables

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Diagram of life cycle

Radiology images

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CT scan

  • Metronidazole, surgery only if complications
Gross description
  • Well circumscribed, firm cavities, usually right sided near liver dome
  • Initially yellow, later odorless, orange brown, pasty, necrotic material resembles anchovy sauce
Microscopic (histologic) description
  • Shaggy necrotic fibrinous zone, granulation tissue, no / rare neutrophils (not actually an "abscess"), peripheral trophozoites up to 60 microns with small eccentric nucleus and cytoplasmic vacuoles that may contain red blood cells
  • Resemble histiocytes
  • Adjacent liver has fibrosis, chronic inflammation and reactive hepatocytes
Microscopic (histologic) images

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Cytology description
  • Use saline wet mounts and stained material
  • 50% positive if material obtained from periphery; very rarely positive if from center of cyst
Positive stains
Differential diagnosis
  • Macrophages:
    • Bean shaped nuclei, fine chromatin, delicate nuclear membrane, small nucleoli
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