Amebiasis is a common cause of diarrhea in infants in low-income countries and an emerging sexually transmitted infection in some developed countries. Amebiasis also causes colitis that can present with diarrhea and/or dysentery that can be acute or last more than 1 week. Abdominal tenderness and weight loss are common with amebic colitis.
Amebic liver abscess presents with right upper quadrant pain. May not present with diarrhea, but will usually have a preceding history of diarrhea.
Rare cause of brain abscess.
Most patients will have traveled to or resided in an endemic area in the 12 months preceding presentation. Oral-anal sexual contact is a risk factor for sexual transmission.
Diagnosis is confirmed by detection of Entamoeba histolytica antigen or DNA in stool or antibodies against the parasite in serum.
Treatment is with nitroimidazoles (including metronidazole or tinidazole) followed by luminal agents such as paromomycin or diloxanide furoate to prevent relapse. Reinfection is common in endemic regions; patients should be counselled on how to reduce the risk of reinfection.
Amebiasis is caused by the parasite Entamoeba histolytica. It causes diarrhea and colitis. Spread of infection from the intestine can result in liver abscess (via haematogenous dissemination). Extension from liver abscess can lead to pleural and pericardial effusion. Rarely, brain abscess may occur
History and exam
Key diagnostic factors
Other diagnostic factors
- generalized abdominal pain
- right upper quadrant abdominal pain
- weight loss
- altered mental status or limb weakness
- guarding and rebound tenderness of the abdomen
- right lung decreased air entry and percussion note
- exposure in endemic areas
- institutionalization of intellectually disabled people
- men who have sex with men
- oral-anal sexual contact
- HIV infection, past or current syphilis infection
- male gender
1st investigations to order
- stool antigen detection
- PCR or qPCR of stool or liver abscess pus for E histolytica DNA
- serum antibody test
Investigations to consider
- stool microscopy
- liver ultrasound
- CT liver/chest/head
- MRI brain
Koji Watanabe, MD, PhD
AIDS Clinical Center
National Center for Global health and Medicine
KW is an author of a number of references cited in this topic.
Dr Koji Watanabe would like to gratefully acknowledge Dr William A. Petri, a previous contributor to this topic. WAP is a consultant for TechLab, Inc. which manufactures diagnostic tests for amebiasis and is also the author of a number of references cited in this topic.
Ran Nir-Paz, MD
Senior Lecturer in Microbiology and Medicine
Department of Clinical Microbiology and Infectious Diseases
Hadassah-Hebrew University Medical Center
RNP declares that he has no competing interests.
Christopher Huston, MD
Assistant Professor of Medicine
Division of Infectious Diseases
University of Vermont College of Medicine
CH declares that he has no competing interests.
- Infectious diarrhea
- Ulcerative colitis
- Pyogenic liver abscess
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