(Redirected from Entamoeba histolytica)


The life-cycle of various intestinal Entamoeba species.
  • Fecal oral transmission of Entamoeba histolytica cyst
  • Most infection asymptomatic
  • Excystation in intestinal lumen
  • Trophozoites adhere and colonizes large intestine forming new cysts or invade the intestinal mucosa to cause colitis or abscesses
  • Liver abscess - 10x more common in men
  • Incubation period usually 2-4 weeks, but may range from a few days to years

Clinical Features

  • Asymptomatic vs. dysentery vs. extraintestinal abscesses
  • Intestinal- several weeks of crampy abdominal pain, weight loss, watery or bloody diarrhea
  • Liver abscess-fever, cough, RUQ or epigastric pain, right-sided pleural pain or referred shoulder pain +/- GI upset
    • Hepatomegaly with tenderness over the liver a typical finding
    • Abscess rupture can involve associated peritoneum, pericardium, or pleural cavity
  • Extrahepatic amebic abscesses in the lung, brain, and skin are rare

Differential Diagnosis


Hepatic abscess

Fever in traveler

Acute diarrhea



Watery Diarrhea

Traveler's Diarrhea



  • CBC
  • Chem
  • LFTs
  • Stool PCR
    • Diagnostic gold standard
    • 100% sensitive and specific
  • Stool or abscess microscopy
    • <60% SN; unreliable diagnostic test[2]
  • Stool, serum, or abscess fluid antigen
  • Indirect hemagglutination (antibody)


  • Abdominal Ultrasound
    • 58-98% SN for liver abscess (depending on size/location)
  • Abdominal CT
    • Alternative to ultrasound; equally effective in identifying abscess


Asymptomatic colonization


Liver abscess

  • Flagyl, tinidazole, paromomycin, or diloxanide
  • Consider drainage of abscess by IR if no response to antibiotics in 5 days, abscess > 5cm, or left lobe involvement


  • Admission
    • Admit if signs of shock, sepsis, or peritonitis
    • Patients with toxic megacolon should be admitted for surgical intervention.
  • Discharge
    • Patients who are non-toxic and able to tolerate oral hydration/PO meds can be discharged with outpatient follow-up

External Links


  1. Marx et al. “Cholera and Gastroenteritis caused by Noncholera Vibrio Species”. Rosen’s Emergency Medicine 8th edition vol 1 pg 1245-1246.
  2. Rayan HZ. Microscopic overdiagnosis of intestinal amoebiasis. J Egypt Soc Parasitol. 2005;35(3):941–951