Alveolar echinococcosis
Alveolar echinococcosis, also referred as hepatic alveolar echinococcosis or E. alveolaris, is a more aggressive and invasive form of hepatic hydatid disease caused by Echinococcus multilocularis. It mimics a slow-growing tumor, as in contrast to E. granulosus it does not form a well defined encapsulated mass, but rather infiltrates the liver and its surrounding structures, especially at the porta hepatis (portal vein, hepatic veins, inferior vena cava (IVC), and the biliary tree).
For a general discussion, particularly epidemiology and pathology, but also for links to other system-specific manifestations, please refer to the article on hydatid disease.
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Terminology
Although the condition is also named as Echinococcus alveolaris or E. alveolaris, note that this is not the species name.
Radiographic features
It commonly presents as large irregular cystic/necrotic masses with a characteristic lobar involvement, peripheral calcifications, and no significant enhancement. Extension into the biliary tree, portal vein, hepatic vein, or IVC is characteristic of this pattern of hydatid disease.
Ultrasound
- large irregular mostly hypoechoic mass with central anechoic areas and scattered peripheral foci of calcification
- peripheral thick hyperechogenicity may be present representing fibrous tissue
- less common presentations representing up to a third of the cases:
- multiple clustered hyperechoic nodules (hailstorm pattern 1)
- pseudocyst characterized by a massive necrotic area
- IVC, hepatic and portal vein invasion may be present
- biliary duct involvement usually characterized by asymmetric/focal intrahepatic biliary tree dilatation
CT
- large (~10 cm) multiloculated/confluent necrotic mass
- irregular margins
- peripheral scattered calcifications
- central hypoattenuating necrotic areas
- diffuse lobar involvement
- usually, no relevant enhancement is observed after intravenous contrast administration
- surrounding fibroinflammatory enhancement may be present on a delayed phase 1
MRI
- T1: intermediate signal intensity
-
T2
- high T2 signal intensity within the multiple small cystic lesions and central necrotic components
- marked low T2 signal intensity at the peripheral fibrotic tissue 1
- MRCP: useful to assess the biliary distortion, compression, and dilatation, as well as communication and extension of the parenchymal cystic/necrotic lesions into the biliary tree 1
- T1 C+ (Gd): no enhancement within the mass lesion
Differential diagnosis
Related Radiopaedia articles
Hepatobiliary pathology
- depositional disorders
- infection and inflammation
- liver abscess
- hepatic hydatid infection
- cirrhosis
- hepatitis
- cholecystitis
- cholangitis
- malignancy
- liver and intrahepatic bile duct tumors
- benign epithelial tumors
- hepatocellular hyperplasia
- hepatocellular adenoma
- hepatic/biliary cysts
- benign nonepithelial tumors
- primary malignant epithelial tumors
- hepatocellular carcinoma
- hepatocellular carcinoma variants
-
cholangiocarcinoma
- intra-hepatic
- mass-forming type
- periductal infiltrating type - Klatskin tumors
- intraductal growing type
- extra-hepatic/large duct type
- intra-hepatic
- biliary cystadenocarcinoma
- combined hepatocellular and cholangiocarcinoma
- hepatoblastoma
- undifferentiated carcinoma
- primary malignant nonepithelial tumors
- hematopoietic and lymphoid tumors
- primary hepatic lymphoma
- hepatic myeloid sarcoma (hepatic chloroma)
- secondary tumors
- miscellaneous
- adrenal rest tumors
- hepatic carcinosarcoma
- hepatic fibroma
- hepatic Kaposi sarcoma
- hepatic lipoma
- hepatic mesenchymal hamartoma
- hepatic myxoma
- hepatic rhabdoid tumor
- hepatic solitary fibrous tumor
- hepatic teratoma
- hepatic yolk sac tumor
- inflammatory myofibroblastic tumor (inflammatory pseudotumor)
- nodular regenerative hyperplasia
- pancreatic rest tumors
- primary hepatic carcinoid
- benign epithelial tumors
- liver and intrahepatic bile duct tumors
- metabolic
- trauma
-
vascular and perfusion disorders
- portal vein related
- hepatic artery related
- hepatic veins related
- inferior vena cava related
- other
- third inflow
- liver thrombotic angiitis
- infra diaphragmatic total anomalous pulmonary venous return (TAPVR)
- hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu disease)