234.3 🩺 內科專科考前版

234.3.0.1 1⃣ Amebic vs Pyogenic Liver Abscess

Feature Amebic Pyogenic
Number Usually solitary Often multiple
Location Right lobe (75%) Variable
Demographics Young male, endemic area / traveler Older, biliary / GI source
Onset Subacute (1-2 wk) Acute
Pus “Anchovy paste”, no PMN Thick yellow, PMN-rich
Bacteria None on Gram stain Polymicrobial often
Serology Anti-E. histolytica + Negative
Treatment Metronidazole + paromomycin ± drainage Antibiotic + drainage
Prognosis Excellent with treatment Variable

234.3.0.2 2⃣ When to Drain Amebic Liver Abscess

  • 5-10 cm

  • Imminent rupture (close to capsule)
  • Pleural / pericardial proximity
  • Failure to respond to medical Tx in 5-7 days
  • Diagnostic uncertainty (rule out pyogenic)
  • Empirical drainage NOT routine

234.3.0.3 3⃣ Travel-Acquired vs Local

  • Travel history essential
  • Mexico, India, Bangladesh, sub-Saharan Africa common origins
  • MSM cases in non-endemic
  • Stool studies + serology + imaging

234.3.0.4 4⃣ Concurrent Intestinal + Liver Disease

  • Liver abscess often without preceding diarrhea
  • But stool studies still positive in some
  • Test for both
  • Treat both if positive

234.3.0.5 5⃣ Serology Limitations in Endemic Areas

  • Antibodies persist after infection for years
  • Cannot distinguish acute from past infection in endemic areas
  • Stool antigen + PCR better for acute diagnosis
  • Combine with clinical + imaging

234.3.0.6 6⃣ Pregnancy + Amebiasis

  • More severe disease
  • Fulminant colitis risk
  • Paromomycin safe (non-absorbed)
  • Metronidazole 1st trim avoided (theoretical)
  • Severe symptomatic 1st trim: metronidazole indicated despite

234.3.0.7 7⃣ HIV + Amebiasis

  • More severe + invasive disease
  • HIV CD4 < 200: increased dissemination
  • Treatment same; monitor + complete course
  • MSM HIV+: increased risk

234.3.0.8 8⃣ 健保 / Taiwan

  • 通報 mandatory
  • 健保 metronidazole + paromomycin + drainage covered
  • US-guided drainage available
  • Travel medicine awareness
  • 盧醫垫 hint: traveler returning from endemic + RUQ pain + fever + bloody diarrhea → amebiasis + liver abscess workup

234.3.0.9 9⃣ Resistance

  • Metronidazole resistance very rare (clinical relevance limited)
  • Treatment failures usually due:
    • Inadequate course
    • Non-compliance
    • Wrong diagnosis
  • Re-treat with same regimen + extend if needed

234.3.0.10 10. Future

  • Vaccine in early development
  • Newer luminal agents (better tolerated)
  • Diagnostics: POC antigen tests for resource-limited settings