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Amoebiasis - Diagnosis
Last reviewed: 03.07.2025
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The simplest and most reliable diagnostics of intestinal amebiasis is microscopic examination of feces to detect vegetative forms (trophozoites) and cysts. Trophozoites are best detected in patients with diarrhea, and cysts in formed stool. Primary microscopy involves examining native preparations from fresh fecal samples with physiological saline. To identify amoeba trophozoites, native preparations are stained with Lugol's solution or buffered methylene blue. To identify cysts, native preparations prepared from fresh or preservative-treated fecal samples are stained with iodine. Detection of amoebas is more effective with immediate examination of feces after prescribing a laxative. Enrichment methods are also used in practice, in particular ether-formalin precipitation. However, the enrichment method can only detect cysts, since trophozoites are deformed. Detection of amoeba cysts alone does not confirm the presence of invasive amoebiasis. In recent years, a sensitive and specific PCR method has been developed that allows for the relatively simple and rapid identification of both E. histolytica and E. dispar in faeces.
In case of clinical data indicating possible intestinal damage, it is recommended to perform a recto- or colonoscopy with obtaining biopsy material. These methods can detect intestinal ulcers, amoebomas, strictures and other pathological changes. A characteristic feature of changes in amebiasis is a focal, rather than diffuse, type of lesion. Diagnostics of extraintestinal amebiasis, in particular liver abscess, is carried out using ultrasound and CT, which allow determining the localization, size, number of abscesses, as well as monitoring the results of treatment. X-ray examination allows identifying a high position of the diaphragm dome, the presence of effusion in the pleural cavity, abscesses in the lungs. If necessary, the contents of the liver abscess are aspirated, but the probability of detecting amoebae in necrotic masses is low, since they are usually located along the periphery of the affected area.
Specific antiamoebic antibodies are detected by serological methods (ELISA, IRIF) in 75-80% of patients with invasive intestinal amebiasis and in 96-100% of patients with extraintestinal lesions; even in asymptomatic carriers of E. histolytica, positive results can reach 10%. These tests are especially useful for the diagnosis of extraintestinal amebiasis, since in these cases invasive stages of E. histolytica are usually absent from the feces. In endemic foci, serological diagnosis of amebiasis is recommended for all patients with suspected amebiasis who are planned to be prescribed glucocorticoids.
[ Indications for consultation with other specialists
Consultation with a surgeon if differential diagnostics with surgical diseases or suspected surgical complications are necessary, in case of liver abscess; consultation with a pulmonologist - in case of lung abscess.
Indications for hospitalization
Clinical, epidemiological, regime during exacerbations: semi-bed rest, table No. 2, 4.
Differential diagnosis of amoebiasis
Differential diagnostics of amebiasis is carried out with balantidiasis, shigellosis, campylobacteriosis, ulcerative colitis, and in tropical countries - with some helminthiases that occur with manifestations of hemorrhagic colitis (intestinal schistosomiasis, trichuriasis, etc.).