• Overview:-intestinal amebiasis

  • Consider other infectious/noninfectious diarrhea causes and gastrointestinal disease in immigrants/travelers from endemic areas

• Intestinal Amebiasis:

  • Diagnostic key: stool examination {routine lab tests: not useful}

  •  Difficulties in performing correct stool examinations

    •  Common false-positives & false-negatives

      • False Negatives caused by:

        • antimicrobial agents

        • soap/tap water enemas (lyse trophozoites)

        • particular to matter (barium or bismuth)-obscures organisms

      • False Positives caused by:

        • leukocytes misread as amebas

        • other amebas confused with E. histolytica

    • Should take multiple stool samples (one "negative" stool result is not sufficient to rule out intestinal amebiasis)

    •  Samples must be properly maintained if not analyzed immediately

  • Presence of many fecal leukocytes suggests some other diagnosis since E. histolytica causes lysis of neutrophils

    • amebiasis differentiation from bacterial diarrheal disease, e.g.shigellosis

  • Indirect hemagglutination test: 70% sensitivity in patients with active intestinal disease-- only 10% sensitivity in asymptomatic cyst carrier

• Overview:Extraintestinal Amebiasis:-

  • Differential includes:

    1. pyrogenic abscess

       • usually multiple abscesses

       • associated with biliary tract disease or other intraabdominal disease

    2. metastatic/primary tumor (includes hemangioma)

  • Typical amebic abscess:

    • single

    • right lobe

• Extraintestinal Amebiasis:

  • Serology helpful if patient not from an endemic area

  • Diagnosis made based on:

    1.  epidemiological information

    2.  radiographic findings

       • ultrasonography-most cost-effective; slightly less sensitive than other techniques

       • MRI

       • CT

       • radioisotope liver scans

    3.  positive serology

       • most sensitive: indirect hemagglutination (95 percent sensitivity in extraintestinal disease) -- does not differentiate present from past infection

Primary Reference: Morgan, Juliette and del Rio, Carlos, Amebiasis in Medicine for the Practicing Physician (Hurst, J. W., ed) Appleton-Lange, 1996, pp. 457-459.