Liver and intrahepatic bile ducts - nontumor
Infectious (nonviral) disorders
Entamoeba histolytica abscess

Author: Komal Arora, M.D. (see Authors page)

Revised: 2 November 2017, last major update May 2012

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PubMed Search: Entamoeba histolytica[TI] liver abscess[TI]

Cite this page: Arora, K. Entamoeba histolytica abscess. PathologyOutlines.com website. http://pathologyoutlines.com/topic/liveramebicabscess.html. Accessed December 14th, 2017.
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 less than 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

Treatment
  • 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
Gross images

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Amebic abscess of liver

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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Trophozoites

Cysts

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