Test code links throughout this Guide refer to the corresponding test in the User's Guide. Most individuals are asymptomatic. Disease in symptomatic individuals may be intestinal or extraintestinal. Patients with intestinal infection may have acute colitis characterized by abdominal pain, tenesmus, or frequent watery stools containing blood and mucus.
Endoscopic examination reveals mucosal ulcerations dispersed throughout a normal-appearing mucosa.
In severe cases, fulminant colitis with perforation or toxic megacolon may occur. Types of extraintestinal disease that have been described include liver abscess, brain abscess, and lung abscess, among others. Diagnosis of amebiasis is based upon the demonstration of organisms in stool or biopsy tissue specimens. Three to six stool examinations are recommended, each permanently stained using a trichrome stain. The microplate assay, however, will not distinguish between pathogenic and non-pathogenic strains of E. histolytica .