Do you have echinococcus on your differential?

Computed tomographic appearance of canine hepatic alveolar echinococcosis

Adina Reuter 1, Jan Wennemuth 1

Background
Alveolar echinococcosis (AE) is a parasitic disease caused by Echinococcus multilocularis, with dogs serving as accidental intermediate hosts. Although ultrasound is typically the first imaging modality for hepatic AE, computed tomography (CT) offers enhanced detail, especially for characterizing hepatic lesions. However, descriptions of CT features in canine AE are limited. This study aimed to characterize CT features of hepatic AE in dogs and assess their comparability to the human Alveolar Echinococcosis Ulm Classification (AEUC).

Methods
This retrospective single-center study included 13 dogs diagnosed with hepatic AE confirmed by histopathology and/or DNA-PCR. CT scans were evaluated for lesion number, size, morphology, attenuation values, wall thickness, presence of mineralization, septation, and involvement of other organs. Contrast enhancement was measured pre- and post-contrast. Lesion classification was attempted using the AEUC used in human medicine.

Results
Two primary lesion types were identified: large, thick-walled cavitary lesions with feathery wall mineralization and soft tissue septation (resembling AEUC IV), and smaller, thin-walled cystic lesions lacking mineralization. All lesions showed no central contrast uptake. The thick-walled lesions had minimal peripheral enhancement, while the thin-walled lesions showed marked wall enhancement. The liver lobes were variably involved, and some cases showed cystic lesions in other organs. Lymphadenopathy and reactive mesenteric fat were common. The findings support a hypothesis that smaller lesions may evolve into larger, mineralized forms.

Limitations
As a retrospective study, it lacked follow-up imaging to confirm lesion progression over time. The absence of control CT scans limits conclusions on lesion evolution. Additionally, the small sample size and reliance on subjective interpretation of enhancement and lesion morphology may introduce bias.

Conclusions
CT imaging of canine hepatic AE reveals characteristic features, notably large cavitary, thick-walled lesions with wall mineralization and smaller, thin-walled lesions. These lesion types may represent different disease stages. The findings suggest CT is valuable in distinguishing AE from other hepatic pathologies and highlight the need for further longitudinal studies to validate lesion progression and enhance diagnostic criteria.

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