Infection occurs following consumption of affected food or water and can lead to dysentery within 3 weeks. Fever and right upper quadrant pain develop later, anywhere from 3 months to years following initial exposure. To diagnose, both serologic and stool testing for E. histolytica are recommended owing to the high sensitivity and low specificity of the serologic antibody test and the low sensitivity and high specificity of the stool antigen test. Imaging may reveal a single cyst with surrounding edema, which is characteristic.
Effective treatment is a two-step process. Metronidazole targets trophozoites that cause liver abscesses followed by paromomycin or diloxanide furoate to eradicate luminal oocysts and prevent reinfection. Aspiration and catheter drainage is necessary if the microbiology or etiology of the liver abscess remains uncertain, patients are not responding to antibiotics, or there is concern for impending rupture with cyst size greater than 6 cm (Jun et al.).
Hydatid cysts. Serologic testing via enzyme-linked immunoassay and radiographic characteristics are used to diagnose cysts caused by Echinococcus, of which there are many species. Imaging typically shows a well-defined cyst with calcifications and budding daughter cysts. Aspiration of an echinococcal cyst carries a risk of anaphylaxis and spread of infection and should only be undertaken if there is serologic and radiographic uncertainty.