Amebic abscess should be considered in every case of solitary hepatic abscess. Amebiasis is caused by the protozoan Entamoeba histolytica. This parasite exists in two forms: an infective cyst stage and a trophozoite stage, which is the form that causes invasive disease. Amebic liver abscess is the most common extraintestinal manifestation of amebiasis. Infection occurs by hematogenous spread from the gut via the portal venous system.
Amebic liver abscesses are 7 to 10 times more frequent in adult men, despite an equal sex distribution of intestinal amebic disease. An abscess can develop after travel exposures of just 4 days.
are classically persistent fever and right-upper-quadrant pain. The presence of diarrhea (reflecting concurrent intestinal amebiasis) is more variable. Presentation usually occurs with 4 months after return from endemic areas. On examination, patients have hepatomegaly and point tenderness over the liver. Rupture of the abscess may cause peritonitis.
Serologic tests for amebic infestation are positive in nearly 100% of affected patients. Ultrasound and CT are the most useful imaging modalities.
Treatment requires systemic metronidazole (750 mg orally three times a day, or 500 mg intravenously every 6 hours, for 7 to 10 days). Needle aspiration should be considered if there is no response to initial therapy or if there is doubt about the diagnosis. The material aspirated contains proteinaceous debris and an “anchovy paste” fluid of necrotic hepatocytes. After completion of the course of metronidazole, the patient should be treated with an intraluminal agent, even if stools are negative for amebas. Intraluminal agents include paromomycin, iodoquinol, and diloxanide furoate. Complications can include bacterial superinfection, erosion into surrounding structures, or free rupture into the peritoneal cavity. Although mortality is infrequent in uncomplicated cases, complicated cases may carry a considerable mortality