Hepatic alveolar echinococcosis with vascular invasion

A 65-year-old farmer did not have any complaints. During annual routine abdomen ultrasound, the cystic lesion was revealed in the left hepatic lobe. The contrast-enhanced abdominal CT was indicated to clarify lesion nature. The clinical examination did not find any pathologic changes.

The CE abdomen CT revealed deformed left liver lobe due to the presence of cystic lesion with numerous septa, scattered calcifications, central hypoattenuating cystic areas (Fig. 1) and a solid component, that did not enhance after CA administration (Fig. 2). The solid component deforms hepatic artery and spreads along with it to the celiac trunk (Fig. 3).  Inferior vena cava and portal vein were also infiltrated and narrowed. Abdomen MRI with MR-cholangiopancreatography were done to receive additional data about lesion structure and individual anatomy for surgery planning. MRI showed moderate diffusion restriction in the solid component of the lesion (Fig. 5 and 6).

Considering curtain contact with farm animals, presence of multiloculated necrotic liver mass with irregular margins, scattered calcifications, central hypoattenuating cystic areas and absence of contrast enhancement alveolar echinococcosis was suspected. Serological tests confirmed the diagnosis.

Alveolar echinococcosis (AE) is a rare parasitic disease, the most aggressive and invasive form of hepatic hydatid disease and is caused by Echinococcus multilocularis. E. multilocularis is endemic in central Europe and the incidence in Europe is estimated to 0.18 cases per 100 000 population [1]. The high-risk groups include farmers, dog-owners [2] and persons who have contact with wild foxes.

AE cysts are slow-growing so AE do not produce any symptoms for a long time. The late symptoms may be weakness, pain and discomfort in the upper abdomen. AE usually may mimic malignant liver lesions.

The diagnosis based on typical findings: non-enhancing cystic-solid lesions detected by different imaging techniques (often accidentally) and the specific serological tests. Ultrasound is the first-line imaging method in the AE diagnosis. AE usually presents as a mostly hypoechoic mass with central anechoic areas and scattered peripheral foci of calcification. CT is a method of choice for the preoperative assessment. CT allows to estimate lesion spreading, vascular invasion and involvement of other organs and systems, first of all, lungs.

In our case anamnesis, presence of calcifications and absence of contrast enhancement of the lesion were the key findings. The pitfall was a vascular involvement that mimics a malignant tumour. 

Surgery is the only radical treatment for AE. Long-term antiparasitic treatment is mandatory. The imaging finds were crucial for surgery planning (right hemihepatectomy). The invasion of the portal vein and hepatic artery walls worsens prognosis and demands vascular plastics.

In conclusion: in case of the asymptomatic cystic lesions with scattered calcifications and absence of contrast enhancement, first of all, exclude hydatid disease. Multiloculated mass with large cystic zones and vascular invasion are features of Alveolar echinococcosis.

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