A 38-year-old man has fever, right upper quadrant pain, and tender hepatomegaly. Ultrasound shows a solitary abscess in the right lobe. Aspirated material is thick, brown, and odourless, and Gram stain shows no bacteria and no parasites. Which statement best explains the failure to demonstrate trophozoites in the aspirated pus?
- A Trophozoites are confined to the wall of the abscess cavity ✓
- B Neutrophil enzymes in the pus destroy all trophozoites
- C Trophozoites encyst inside the abscess cavity
- D Antibodies in the pus lyse the trophozoites
Correct answer: A. Trophozoites are confined to the wall of the abscess cavity
Explanation
In amoebic liver abscess the necrotic centre contains acellular proteinaceous debris, the classic 'anchovy sauce' pus, which is bacteriologically sterile and usually devoid of amoebae. Trophozoites are found only in the wall of the cavity, so examination of the wall or adjacent tissue may reveal them while the pus itself does not. Cysts are never formed in human tissues, which rules out option C, and the pus is largely lysed hepatocytes rather than neutrophilic exudate.
Reference: Paniker's Textbook of Medical Parasitology, 8th ed.
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