Cyst characteristics of the four echinococcal species
Species
Larval form in humans
Cyst components
Cyst growth
E. granulosus
Cystic, unilocular, expansile
Metacestode has an internal germinative layer (endocyst) surrounded by a parasite-derived acellular laminated layer (exocyst), surrounded by a host-derived adventitial layer (pericyst).
Cells bud internally within the cystic cavity, then vacuolate and become "brood" capsules. Protoscolices develop within the brood capsules.
E. multilocularis
<5%
Multilocular, infiltrative
Very thin laminated layer only and no pericyst, which enables tissue invasion.
Germinative layer of metacestode proliferates within cyst and exogenously to infiltrate host tissue. Cells from the germinative layer can detach and metastasize to other organs.
E. vogeli and
E. oligarthus
Polycystic, expansile
Large cysts with multiple vesicles are separated by septa lined by germinative epithelium. Externally, cyst is surrounded by fibrous tissue.
Brood capsules bud internally from germinative epithelium. An expansile and infiltrative polycystic mass develops.
Classification of echinococcal cysts
Gharbi classification
WHO classification
Grouping
Type I
Type CE 1
Group 1- Active group:
Cysts developing and are usually fertile
Type II
Type CE 2
Type III
Type CE 3
Group 2- Transition group:
Cysts starting to degenerate, but usually still contain viable protoscoleces
Type IV
Type CE 4
Group 3- Inactive group:
Degenerated or partially/totally calcified cysts, very unlikely to contain protoscolices
Type V
Type CE 5
Classification of echinococcal cysts and option for treatment modalities stratified by cyst stage
WHO-IWGE
Description
Stage
Treatment practiced
Recommendation
CE1
Unilocular unechoic cystic lesion with double line sign
Active
Surgery, percutaneous and medical therapies
>5 cm: PAIR + albendazole
<5 cm: Albendazole alone
CE2
Multiseptated, "rosette-like" "honeycomb" cyst
Active
Surgery and medical therapy
Albendazole + non-PAIR percutaneous Tx or surgery
CE3A
Cyst with detached membranes (water-lily-sign)
Transitional
Surgery, percutaneous and medical therapies
>5 cm: PAIR + albendazole
<5 cm: Albendazole alone
CE3B
Cyst with daughter cysts in solid matrix
Transitional
Surgery and medical therapies
Albendazole + non-PAIR percutaneous Tx or surgery
CE4
Cyst with heterogenous hypoechoic/hyperechoic contents; no daughter cysts
Inactive
No treatment
No treatment
CE5
Solid plus calcified wall
Inactive
No treatment
No treatment
PAIR: Puncture, Aspiration, Injection, Reaspiration; WHO-IWGE: Informal Working Groups on Echinococcosis. (2001)
Cyst aspiration or biopsy — Percutaneous aspiration or biopsy may be required to confirm the diagnosis by demonstrating the presence of protoscolices, hooklets, or hydatid membranes.
Active cysts:
• clear watery fluid
• scolices and
• ? pressure
Inactive cysts:
• •cloudy fluid
• w/o detectable scolices and
• •do not have elevated pressure
Protoscolices or degenerated hooklets can be demonstrated in sputum or bronchial washings.
Nonspecific leukopenia or thrombocytopenia, mild eosinophilia, and nonspecific liver function abnormalities
Can grow from 1 to 50 mm/year
Indications for ? for liver chinococcosis:
1.Removal of large >10cm developing and transitional cysts with multiple daughter
2. Single superficially liver cysts that may rupture spontaneously or as a result of trauma. Open surgery only if percutaneous Tx is not available
3. Infected cysts when percutaneous Tx is not available
4. As an alternative to percutaneous Tx for communicating with biliarytree
5. Mx of cysts exerting pressure on adjacent vital organs.
Contraindications
1. general condition is very poor
2. multiple cysts or cysts that are difficult to access
3. inactive, totally calcified asymptomatic cysts
4. very small cysts
Protoscolicidal agents (20%NaCl) for at least 15 min