Diagnostic Ultrasound - Abdomen and Pelvis

Hepatic Echinococcus Cyst
Diagnoses: Liver
TERMINOLOGY
• Infection of humans caused by larval stage of Echinococcus
granulosus or Echinococcus multilocularis
IMAGING
• Best diagnostic clue: Membranes± daughter cysts in
complex heterogeneous mass
• E. granulosus
○ Anechoic cyst with double echogenic lines separated by
hypoechoic layer
○ Honeycomb cyst, multiple septations
○ "Water lily" sign: Complete detachment of membrane
○ "Snowstorm pattern": Anechoic cyst with internal debris
and hydatid sand
• E. multilocularis
○ Single/multiple echogenic lesions
○ Irregular necrotic lesions with microcalcifications
○ Ill-defined infiltrative solid masses
KEY FACTS
TOP DIFFERENTIAL DIAGNOSES
• Hemorrhagic or infected cyst
• Complex pyogenic abscess
• "Cystic" metastases
• Biliary cystadenocarcinoma
PATHOLOGY
• Caused by larval stage of Echinococcus tapeworm
○ E. granulosus: Most common form of hydatid disease,
unilocular
○ E. multilocularis: Less common but aggressive
CLINICAL ISSUES
• Serologic test positive in more than 80% of cases
DIAGNOSTIC CHECKLIST
• Rule out other complex or septate cystic liver masses
(Left) This graphic shows an
eccentric cystic mass (the
pericyst or mother cyst) ſt
with numerous peripheral
daughter cysts, or scolices, st
within in the right lobe of the
liver. (Right) Gross photograph
of the liver shows a hydatid
cyst containing multiple
daughter cysts . The fibrous
rim can be seen
surrounding the cyst.
(Courtesy G. Gray Jr., MD.
From: DP: Spleen.)
(Left) Transverse abdominal
US shows an echinococcal cyst
containing multiple peripheral
daughter cysts ſt and central
heterogeneous content st in
the left lobe of the liver. Note
the posterior acoustic
enhancement . (Right) Axial
contrast enhanced CT
performed in the same patient
shows a large multilocular
well-defined cystic mass in the
left lobe of the liver ſt. The
cystic mass has thick wall with
a tiny focus of calcification st
and multiple septations .
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