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Liver and intrahepatic bile ducts-nontumor

Infectious (non-viral) disorders

Entamoeba histolytica abscess


Reviewers: Komal Arora, M.D. (see Reviewers page)
Revised: 27 June 2012, last major update May 2012
Copyright: (c) 2004-2012, PathologyOutlines.com, Inc.

General
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● Also called amebic abscess; more common than pyogenic abscess worldwide, but not in US (Med Clin North Am 1989;73(4):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

Treatment
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● Metronidazole, surgery only if complications

Clinical images
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Diagram of life cycle


CT scan

Gross description
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● Well-circumscribed, firm cavities, usually right sided near liver dome
● Initially yellow, later odorless, orange-brown, pasty, necrotic material resembles anchovy sauce

Clinical images
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Amebic abscess of liver

Micro description
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● 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

Micro images
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Trophozoites


Cysts

Cytology description
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● Use saline wet mounts and stained material
● 50% positive if material obtained from periphery; very rarely positive if from center of cyst

Positive stains
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● PAS, iron hematoxylin, Diff-Quik

Differential diagnosis
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● Macrophages: bean-shaped nuclei, fine chromatin, delicate nuclear membrane, small nucleoli

End of Liver and intrahepatic bile ducts-nontumor > Infectious (non-viral) disorders > Entamoeba histolytica abscess


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