Extraintestinal Amebiasis

Clinical History

A 30-years-old patient from Mali presented with fever and chest pain, and a five-days history of lower limbs dysaesthesia with walking impairment and urinary retention. Laboratory tests, CT and MRI were performed.

Imaging Findings

Contrast-enhanced CT showed a soft-tissue bulge in the right costovertebral groove at T4-T5 associated with mild hypodense collection in the erector spine muscle and suspicious involvement of the spinal cord. Enlarged lymphonodes, partially colliquated, were identified in the mediastinum, and multiple hypodense nodules were detected in the liver.
MRI was required, and detected a well-defined right paravertebral mass with T1-hypointense and T2-hyperintense central areas consistent with necrosis and T1-hyperintense capsule after gadolinium injection. There was compression of the spinal cord through the T4-T5 intervertebral foramen and bone marrow oedema at this level. Hepatospecific phase sequences demonstrated T1-hypointensity of the hepatic nodules.
A US guided drainage of the paravertebral mass was therefore performed, which showed a “chocolate-coloured” content.
Laboratory tests revealed moderate phlogosis indices elevation and significantly high Enzyme Immunoassay (EIA) title of Entamoeba Histolytica antibodies.
CT obtained one year later, after specific treatment, demonstrated resolution of the paravertebral, hepatic abscesses and lymphnodes enlargement.

Discussion

Amoebiasis is a parasitic disease that can occur at any age in healthy and immunocompromised patients among the lower socioeconomic classes in tropical and subtropical climates; other risk factors include immigrants from endemic areas. Usually, humans acquire amoebiasis by ingesting cysts of E.Histolytica in contaminated food or drinking water, from swimming in contaminated lakes or inhaling dust with amoebic cysts. These forms become trophozoites in the small bowel, constituting the invasive form of the parasite [1].
Entamoeba causes an intense inflammatory reaction, followed by extensive necrosis; however, because of a lack of cicatrisation process, there is restitutio ad integrum of the affected organs, as we observed in our patient at the CT control one year later [4].
Hepatic abscess is the most common extraintestinal lesion, resulting from trophozoite embolization in the portal venous system via the mesenteric-splanchnic circulation. Thoracic infection may result from several routes: direct extension from a liver abscess to the thorax, haematogenous spread (hepatic, pulmonary or vertebral veins), rarely aspiration; common findings include parenchymal consolidation and cavitation, pleural effusion or frank empyema [3]. Among other extrahepatic extensions of amoebic abscess described in literature (brain, chest wall, pleural cavity, pericardium), the paraverberal localisation detected in our case has never been reported [2].
Because of haemorrhages in the cavities, the abscesses are sometimes filled with a chocolate-coloured, pasty material known as “anchovy paste”. Secondary bacterial infection may make these abscesses purulent. In agreement with literature, the pus culture of our patient was sterile because the parasite exists in the wall of the abscess [5].
Imaging of amoebic abscesses with contrast-enhanced CT demonstrates round, well-defined lesions. An enhancing wall 3–15 mm in thickness and a peripheral zone of edema around the abscess are characteristic. The central abscess cavity may show complex fluid content, multiple septa or fluid-debris levels and, rarely, air bubbles or haemorrhage [2].
MR is useful for central nervous system localisations, depicting amoebic abscesses as homogeneous T1-hypointense and T2-hyperintense images, respectively. Visualization of perilesional oedema on T2-weighted MR images occurs in only 50% of cases [2].
Though nonspecific, in patients coming from endemic areas, imaging features can lead to the right diagnosis if combined with clinical signs and serological tests. Currently, the ELISA test in serum and feces appears to be the most reliable test with a virtual absence of false-negative results. Treatment consists of specific antiamoebic drugs, mainly metronidazole and ketoconazole [4].

Differential Diagnosis List

Final Diagnosis

Extraintestinal Amoebiasis with hepatic and paravertebral abscesses

URL:	https://www.eurorad.org/case/12244
DOI:	10.1594/EURORAD/CASE.12244
ISSN:	1563-4086