Amebiasis is caused by the protozoan Entamoeba histolytica. Most infections are asymptomatic; clinical manifestations include amebic dysentery and extraintestinal disease. Worldwide, approximately 40 to 50 million people are infected annually . Extraintestinal manifestations include amebic liver abscess and other more rare manifestations such as pulmonary, cardiac, and brain involvement .
The extraintestinal manifestations of amebiasis will be reviewed here. Issues related to intestinal infection with E. histolytica are discussed separately, including epidemiology, pathogenesis, clinical manifestations, diagnosis, treatment, and prevention. (See "Intestinal Entamoeba histolytica amebiasis".)
AMEBIC LIVER ABSCESS
Amebic liver abscess is the most common extraintestinal manifestation of amebiasis. Amebae establish hepatic infection by ascending the portal venous system .
Epidemiology — Amebic liver abscess (and other extraintestinal disease) is 7 to 10 times more common among adult men than other demographic groups, despite equal gender distribution of colonic amebic disease [4-7]. It is observed most frequently in the fourth and fifth decades of life . The reasons for these observations are not fully understood; suggested mechanisms include hormonal effects and a potential role of alcoholic hepatocellular damage in creating a nidus for portal seeding .
In developed countries, amebiasis is generally seen in migrants from and travelers to endemic areas. Amebiasis is relatively uncommon among short-term travelers, but amebic liver abscesses can occur after travel exposures as short as four days . In one study, 35 percent of travelers with amebic liver abscess had spent less than six weeks in an endemic area .