If there is no diarrhea, the trophozoites will encyst before passage in the stool. It is the cyst which causes disease, and the usual route is through fecal contamination of food or water. The diagnosis is made by finding the cyst in formed stools or the trophozoite in liquid stool. The clinical manifestations of symptomatic intestinal amebiasis are intermittent diarrhea, progressing to fulminant attacks of amebic dysentery with high fever, severe abdominal cramps, and profuse bloody diarrhea with tenesmus. In these patients, trophozoites are numerous in stools and on the material obtained from ulcers in the cecum and rectum.
Hepatic amebiasis occurs as a result of the parasite invading of the liver via the portal vein.
This may be followed by the development of a single hepatic abscess in the posterior portion of the right lobe of the liver. Clinical findings of the abscess are fever, night sweats, weight loss, and sometimes, tender hepatomegaly. Occasionally, an abscess will extend into the right pleural cavity and lung. These people will present with cough, pleural pain, fever and leukocytosis as a rule. A secondary bacterial infection is frequent.