234.2 📚 國考版

234.2.0.1 必背 — E. histolytica vs Non-Pathogenic

  • E. histolytica = pathogenic (must distinguish)
  • E. dispar, E. moshkovskyi = non-pathogenic (morphologically identical)
  • Differentiation: stool antigen + PCR (not microscopy)

234.2.0.2 必背 — Forms

  • Cyst (4 nuclei, environmental, chlorine-resistant)
  • Trophozoite (motile, ingested RBCs = pathognomonic E. histolytica)

234.2.0.3 必背 — Clinical

  • 90% asymptomatic (carriers)
  • Acute amebic colitis: bloody diarrhea + mucus + tenesmus + flask-shaped ulcers
  • Fulminant colitis (5%): peritonitis + perforation + high mortality
  • Ameboma: granulomatous mass mimicking CA
  • Amebic liver abscess (extra-intestinal #1): RUQ pain + fever + hepatomegaly, solitary right lobe, “anchovy paste”

234.2.0.4 必背 — Diagnosis

  • Stool antigen test (preferred — distinguishes E. histolytica from non-pathogenic)
  • PCR multiplex
  • Stool O+P (× 3 days)
  • Serology for liver abscess (positive in invasive)
  • Imaging (US, CT) for liver abscess
  • “Anchovy paste” + trophozoites at periphery on aspirate

234.2.0.5 必背 — Treatment (Two-Drug Approach)

234.2.0.5.0.1 Symptomatic Disease
  • Tissue amebicide: Metronidazole 750 mg tid × 7-10 d (or tinidazole)
  • PLUS Luminal amebicide: Paromomycin 25-35 mg/kg/d × 7-10 d (or iodoquinol)
234.2.0.5.0.2 Liver Abscess
  • Same regimen + drainage if > 5-10 cm or imminent rupture or refractory
234.2.0.5.0.3 Asymptomatic Carrier
  • Paromomycin alone (eliminate cysts, prevent transmission)

234.2.0.6 必背 — Liver Abscess Triad

  • RUQ pain + fever + hepatomegaly in patient from endemic area or traveler

234.2.0.7 必背 — Liver Abscess Imaging

  • Solitary right lobe predominant (vs pyogenic often multiple)
  • Hypodense / hypoechoic
  • US first-line

234.2.0.8 必背 — Why Two Drugs

  • Metronidazole kills tissue trophozoites but not lumenal cysts
  • Paromomycin kills lumenal cysts but not tissue trophozoites
  • Both needed to prevent relapse + transmission

234.2.0.9 必背 — Anchovy Paste

  • Liver abscess aspirate appearance
  • “Brown” or “red” thick fluid (necrotic liver + blood)
  • No PMN (vs pyogenic abscess)
  • Trophozoites at periphery only