Section: Hepatobiliary Sub-section: Liver Curriculum: Curriculum, page 86

Definition

A parasitic illness caused by the tapeworm Echinococcus

Epidemiology

E. granulosus – worldwide in Mediterranean, Asia, Africa, South America and Australia
- More common
E. multilocularis - endemic North America, Asia and some European countries
- More serious

Caused by parasitic Tapeworm Echinococcus.
Liver most common organ but can metastasise to lung, brain, bones and local extension in abdomen, retroperitoneum or diaphragm.

Definitive host: Dog
Intermediate hosts: , ungulates (sheep, pigs, goats, horses)
- Humans accidental intermediate host
  - Iingestion of eggs which are excreted by carnivores
  - The eggs grow and form a cyst (mainly in the liver)

Hydatid cysts are round filled with a clear fluid
Three layers
- Pericyst - fibrous layer
- Ectocyst: acellular laminated layer
- Endocyst: germinating membrane
Cysts expand causing a granulomatous inflammatory reaction leading the cyst to be walled off by fibrous tissue.
Maturing cysts may develop daughter cysts and septations.
Peripheral calcifications are common

Clinical presentation – asymptomatic, incidental liver lesions.
RUQ pain, loss of appetite.
Complications from cysts:
- leakage, rupture causing anaphylaxis,
- cholangitis due to bile duct obstruction by daughter cyst or rupture into duct
- secondary infection of cyst
Cyst classifications:
- WHO classification of cystic echinococcus

Ultrasound

Characteristics
- Hydatid sand (scolices in cyst fluid from ruptured vesiculae)
- Floating membranes
- Daughter cysts
- Vesicles in cyst CT
Calcifications, internal structures and complications MRI
Superior for cyst wall defect, biliary communication and neural involvement.

Serology

Serological useful to confirm radiological diagnosis.
Not all patients will have detectable immune response (dependent on antigen secretion)

Surgery
- Complicated cysts (biliary fistula), multiseptated or daughter cysts, large superficial cysts with high risk of perforation.
- Best chance of cure.
- Albendazole usually given to reduce risk of anaphylaxis & secondary echinococcosis.
Percutaneous
- PAIR (puncture, aspiration, injection, re-aspiration).
  - USS guidance, injection of protoscolicidal agent (hypertonic saline and EtOH).
  - 97% success rate.
  - Not great for cysts with daughter cysts.
  - Contraindicated if biliary communication (risk of sclerosing cholangitis).
  - Concurrent albendazole.
Medical
- Small cysts <5cm without daughter cysts or septations.
- Or patients who cannot undergo surgery or perc drainage.
- 1/3 cure rate.
Liver transplant if advanced liver failure

Disseminated echinococcosis

Spontaneously rupture can induce anaphylaxis or lead to secondary disseminated cystic echinococcosis.
Can also arise as a complication of surgery for hydatid disease