Diagnostic Ultrasound - Abdomen and Pelvis

Hepatic Echinococcus Cyst
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Diagnoses: Liver
DIFFERENTIAL DIAGNOSIS
Hemorrhagic or Infected Cyst
• Complex cystic heterogeneous mass
• Septations, fluid-levels, and mural nodularity
• Calcification may or may not be seen
Complex Pyogenic Abscess
• "Cluster of grapes": Confluent complex cystic lesions
"Cystic" Metastases
• e.g., cystadenocarcinoma of pancreas or ovary
• May present with debris, mural nodularity, rim
enhancement
Biliary Cystadenocarcinoma
• Rare, multiseptated water density cystic mass
• No surrounding inflammatory changes
PATHOLOGY
General Features
• Etiology
○ Caused by larval stage of Echinococcus tapeworm
– E. granulosus and E. multilocularis
• Carried by sheep, transmitted to humans by dog or fox
○ Humans are incidental hosts
• Larvae → portal vein → liver (75%)
• E. granulosus
○ Develop into hydatid stage (4-5 days) within liver
○ Hydatid cysts grow to 1 cm during first 6 months, 2-3 cm
annually
• E. multilocularis
○ Larvae proliferate and penetrate surrounding tissue
○ Cause diffuse and infiltrative granulomatous reaction,
simulating malignancy
○ Necrosis → cavitation → calcification
Microscopic Features
• Cyst fluid content: Antigenic, pale yellow, neutral pH
• Endocyst: Gives rise to daughter vesicles/brood capsule,
which may detach, form sediment, or produce daughter
cysts
• Ectocyst: Acellular substance secreted by parasite
• Pericyst: Host response forming layer of
granulation/fibrous tissue
• Diagnosis
○ Serologic tests positive in more than 80% of cases
○ Percutaneous aspiration of cyst fluid
– Danger of peritoneal spill and anaphylactic reaction
Demographics
• Age
○ Hydatid disease usually acquired in childhood
○ Not diagnosed until 30-40 years of age
• Gender: M = F
• Epidemiology
○ E. granulosus: Mediterranean region, Africa, South
America, Australia, and New Zealand
○ E. multilocularis: France, Germany, Austria, USSR, Japan,
Alaska, and Canada
Natural History & Prognosis
• Complications
○ Compression/infection or rupture into biliary tree
○ Rupture into peritoneal or pleural cavity
○ Spread of lesions to lungs, heart, brain, and bone
• Prognosis
○ E. granulosus: Good
○ E. multilocularis: Fatal in 10-15 years untreated
Treatment
• E. granulosus
○ Medical: Albendazole/mebendazole
○ Direct injection of scolicidal agents
○ PAIR procedure: Puncture, aspiration, injection,
respiration
○ Surgical: Segmental or lobar hepatectomy
• E. multilocularis
○ Partial hepatectomy/hepatectomy + liver transplant
DIAGNOSTIC CHECKLIST
Consider
• Rule out other complex or septate cystic liver masses
○ Biliary cystadenoma, pyogenic liver abscess, cystic
metastases, and hemorrhagic or infected cyst
○ E. multilocularis imaging and clinical behavior simulates
solid malignant neoplasm
Image Interpretation Pearls
• Daughter cysts can float freely within mother cyst
○ Altering patient's position may change position of
daughter cysts
CLINICAL ISSUES
Presentation
SELECTED REFERENCES
• Most common signs/symptoms
○ Cysts: Initially asymptomatic
– Symptomatic when size ↑/infected/ruptured
○ Pain, fever, jaundice, hepatomegaly
○ Allergic reaction; portal hypertension
• Clinical profile
○ Middle-aged patient with right upper quadrant pain,
palpable mass, jaundice
• Lab data
○ Eosinophilia; ↑ serologic titers
○ ± ↑ alkaline phosphatase/gamma-glutamyl
transpeptidase (GGTP)
http://radiologyebook.com/
1. Qian LJ et al: Spectrum of multilocular cystic hepatic lesions: CT and MR
imaging findings with pathologic correlation. Radiographics. 33(5):1419-33,
2013
2. Li Q et al: Echinococcal cysts of the liver and spleen: complex hepatic and
splenic cystic lesions. Ultrasound Q. 28(3):205-7, 2012
3. Marrone G et al: Multidisciplinary imaging of liver hydatidosis. World J
Gastroenterol. 18(13):1438-47, 2012
4. Brunetti E et al: Expert consensus for the diagnosis and treatment of cystic
and alveolar echinococcosis in humans. Acta Trop. 114(1):1-16, 2010
5. Pedrosa I et al: Hydatid disease: radiologic and pathologic features and
complications. Radiographics. 20(3):795-817, 2000