Amoebiasis is caused by Entamoeba histolytica (an amoeboid protozoan) and spread by the faecal-oral route. It is estimated that 10% of the world's population is chronically infected. Infection can be asymptomatic, cause mild diarrhoea or severe amoebic dysentery. Amoebiasis also causes liver and colonic abscesses..

Amoebic dysentery

• profuse, bloody diarrhoea
• there may be a long incubation period
• stool microscopy may show trophozoites if examined within 15 minutes or kept warm (known as a 'hot stool')
• treatment
  • oral metronidazole
  • a 'luminal agent' (to eliminate intraluminal cysts) is recommended usually as well e.g. diloxanide furoate

Amoebic liver abscess

• initial amoebic colitis → weeks later spreads via portal circulation → liver abscess
• usually a single mass in the right lobe (may be multiple). The contents are often described as 'anchovy sauce'
• features
  • fever
  • right upper quadrant pain
  • systemic symptoms e.g. malaise
  • hepatomegaly
• investigations
  • ultrasound
  • serology is positive in > 95%
• management
  • oral metronidazole
  • a 'luminal agent' (to eliminate intraluminal cysts) is recommended usually as well e.g. diloxanide furoate