Amebic Lung Abscess

What is Amebic Lung Abscess?

Amoebic lung abscess is a purulent inflammation of the lung tissue as a result of the necrotizing action of the dysenteric amoeba brought by the bloodstream from the colon.

Causes of Amebic Lung Abscess

The pathogenic agent is Entamaeba histolytica. There are three forms of liver damage to enameba: cyst as a stable form, a weakly pathogenic regressive form, and a histolytic form that causes both dysentery and liver abscess.

Pathogenesis during Amebic Lung Abscess

The swallowed mature amoeba cysts in the intestinal lumen are transformed into vegetative forms, which, under conditions of decreasing local resistance of the mucous membrane of the large intestine, acquire the ability to penetrate into the mucous membrane and submucosal layer of the intestine with the formation of microabsities and ulcers in them.

As a result of hematogenous dissemination from the intestinal wall, tissue forms of amoeba can penetrate into any organs and tissues, most often into the liver, less frequently into the lungs and brain, causing the development of necrosis in them, followed by abscess formation.

Symptoms of Amebic Lung Abscess

Amoebic lung abscess develops as a result of hematogenous dissemination from other organs, as well as the direct spread of the process from the liver. In the zone of amoebae localization, cell lysis develops with preservation of collagen structures and slight lymphocytic and histiocytic proliferation. On the periphery of the hearth tissue forms of amoeba are found. Adherence of purulent flora leads to the formation of purulent abscess. Suppuration is accompanied by severe general intoxication.

The incubation period of the disease is from 1 week to several months. In accordance with the WHO classification, intestinal (acute and chronic with various complications), extraintestinal (with damage to various systems and organs, most often the liver) and cutaneous amebiasis are distinguished.

The hematogenous introduction of amoebas into the lungs causes the development of amoebic pneumonia, manifested by febrile reactions, chest pains, painful coughs with scanty brownish sputum in which tissue forms of amoebas can be detected. The accession of a secondary infection causes the purulent fusion of the foci of necrosis and the formation of amoebic lung abscess. An X-ray examination first reveals an infiltrative focus, often in the right lung, resembling a tuberculous lesion. Further, a rounded shadow with moderately pronounced perifocal infiltration is detected, and in the case of drainage of the abscess cavity into the bronchus, a horizontal level is detected.

The course of the disease is long; a pulmonary abscess may break into the pleural cavity with the development of pyopneumothorax.

The prognosis of amebic lung abscess is serious, with the development of pyopneumothorax or bronchohepatic fistula – poor.

Diagnosis of Amebic Lung Abscess

The diagnosis of amoebic lung abscess is based on a combination of clinical data that demonstrate intestinal or pulmonary manifestations of amebiasis, x-ray findings, confirmed by the detection of amoebas in sputum or pleural fluid, and sometimes in fecal masses (in the presence of a colitis clinic); serological diagnostic methods are used – complement-binding reaction (CSC), fluorescent antibody method (MFA), enzyme-labeled antibody reaction (REMA). Differential diagnosis is carried out with tuberculosis, lung abscesses of a different origin, lung tumors.