Innovation in hepatic alveolar echinococcosis imaging: best use of old tools, and necessary evaluation of new ones

Abstract

Hepatic Alveolar Echinococcosis (HAE), caused by larvae of Echinococcus multilocularis, is a rare but potentially lethal parasitic disease. The first diagnostic suspicion is usually based on hepatic ultrasound exam performed because of abdominal symptoms or in the context of a general checkup; HAE diagnosis may thus also be an incidental finding on imaging. The next step should be Computed Tomography (CT) or Magnetic Resonance Imaging (MRI). They play an important role in the initial assessment of the disease; with chest and brain imaging, they are necessary to assess the PNM stage (parasite lesion, neighboring organ invasion, metastases) of a patient with AE. Performed at least yearly, they also represent key exams for long-term follow-up after therapeutic interventions. Familiarity of radiologists with HAE imaging findings, especially in the endemic regions, will enable earlier diagnosis and more effective treatment. Fluorodeoxyglucose Positron Emission Tomography (FDG-PET) is currently considered to be the only noninvasive, albeit indirect, tool for the detection of metabolic activity in AE. Delayed acquisition of images (3 hrs after FDG injection) enhances its sensitivity for the assessment of lesion metabolism and its reliability for the continuation/withdrawal of anti-parasite treatment. However, sophisticated equipment and high cost widely limit PET/CT use for routine evaluation. Preliminary studies show that new techniques, such as contrast-enhanced ultrasound (US), Dual Energy CT or Spectral CT, and Diffusion-Weighted MRI, might also be useful in detecting the blood supply and metabolism of lesions. However, they cannot be recommended before further evaluation of their reliability in a larger number of patients with a variety of locations and stages of AE lesions.

Multimodality imaging in diagnosis and management of alveolar echinococcosis: an update

“…Conventional imaging methods, including x-ray, ultrasonography (US), computed tomography (CT), and magnetic resonance imaging (MRI), have been used in the diagnosis, follow-up, and management of AE for several years (13). Recently, there have been new studies on the diagnosis and follow-up of the disease…”

“…It is an adequate and efficient imaging modality in screening AE lesions. Since it is cheap, readily available, and does not contain radiation, US can be used in endemic regions as a fast diagnostic tool in large populations (13,14). Involvement of the liver is seen as mass lesions, which show a mixed heterogeneous echogenic pattern with irregular contours, including cystic necrotic areas and multiple distributed calcific foci.…”

“…Involvement of the liver is seen as mass lesions, which show a mixed heterogeneous echogenic pattern with irregular contours, including cystic necrotic areas and multiple distributed calcific foci. Less typical sonographic appearance is the hailstorm pattern with multiple hyperechogenic solid lesions (13,15). This appearance is suggested to represent early AE lesions.…”

“…Involvement of the hepatic veins, vena cava inferior, and portal vein and its branches can be evaluated with Doppler imaging. In addition, involvement and dilatation of the intrahepatic biliary ducts secondary to mass effect or invasion can be shown sonographically (13,17) (Fig. 1).…”

“…CT is the primary imaging modality in detecting the anatomic location and dissemination of the lesions, characterization of the lesions, and detection of the typical calcifications (3,13). It is useful in evaluating the relationship of the hepatic lesions with the vascular structures and bile ducts.…”