liver hydatid cyst : definition and classification.

1. Dr Karrar Adil

2. Introduction :
 Human echinococcosis is a zoonotic disease that
is caused by parasites, namely tapeworms of the
genus Echinococcus.
 The two most important forms in humans are
cystic echinococcosis (hydatidosis) and alveolar
echinococcosis.
 Humans are infected through ingestion of
parasite eggs in contaminated food, water or soil,
or after direct contact with animal hosts.

3.  A number of herbivorous animals act as intermediate
hosts of Echinococcus. They become infected by
ingesting the parasite eggs in contaminated food and
water, and the parasite then develops into larval stages
in the viscera.
 Carnivores act as definitive hosts for the parasite, and
harbour the mature tapeworm in their intestine. The
definitive hosts are infected through the consumption
of viscera of intermediate hosts that contain the
parasite larvae.
 Humans act as accidental intermediate hosts in the
sense that they acquire infection in the same way as
other intermediate hosts, but are not involved in
transmitting the infection to the definitive host.

4.  The genotype causing the great majority of cystic
echinococcosis infections in humans is principally
maintained in a dog–sheep–dog cycle.
 Alveolar echinococcosis usually occurs in a
wildlife cycle between foxes or other carnivores
with small mammals (mostly rodents) acting as
intermediate hosts. Domesticated dogs and cats
can also act as definitive hosts.
 Liver is commonly involved (65%); lungs (25%);
muscles (5%); bones(3%); rarely kidneys, brain,
spleen.

5. Hydatid cyst structure :
It has got three layers :
1- the pericyst (Adventitia) (pseudocyst) :
 consists almost entirely of host cells.
 is an inseparable fibrous tissue due to reaction of the liver to
the parasite.
2- Laminated membrane (ectocyst) :
 formed by the parasite itself.
 is elastic white covering, easily separable from the adventitia.
3- Germinal epithelium (endocyst) :
 is the only living part, lining the cyst.
 secretes hydatid fluid, brood capsules with scolices. Once
brood capsules disintegrate, it grows into daughter cysts.

7. Echinococcosis Classification :
• Cystic echinococcosis (Classic Hydatid cyst):
 caused by Echinococcus granulosus.
 most common form.
• Alveolar echinococcosis :
 also known as alveolar hydatid disease and small fox
tapeworm.
 caused by Echinococcus multilocularis.
 The second most common form.
• Polycystic echinococcosis :
 also known as human polycystic hydatid disease.
 caused by Echinococcus vogeli.

8. Gharbi ultrasound based classification of
liver hydatid cysts (1981) :
• Type 1 : Pure fluid collection.
• Type 2 : Fluid collection with split wall (Membrane
separation).
• Type 3 : Fluid collection with septa.
• Type 4 : Heterogeneous appearance
(hypo + hyperechoic).
• Type 5 : Reflecting thick walls (completely calcified).

10. WHO classification of hepatic
hydatid cyst :
 is used to assess the stage of hepatic hydatid
cysts on ultrasound and is useful in deciding
the appropriate management depending on the
stage of the cyst.

11.  This classification was proposed by the WHO in
2001 and remains the most widely used
classification for hepatic hydatid cysts.
 Cyst stages as described by the classification
are defined by their observable physical
characteristics and account for changes in
parasite activity/viability.

12. Classification :
1) Type - CL :
 Active.
 Unilocular.
 no cyst wall.
 early stage.
 not fertile.

13. 2) Type - CE 1 :
 Active.
 cyst wall present.
 hydatid sand
present.
 Fertile.

14. 3) Type - CE 2 :
 Active.
 multivesicular rosette
like cyst wall.
 Fertile.

15. 4) Type- CE 3 :
 Transitional.
 detaching laminated
membrane.
 water-lily sign.
 beginning of
degeneration.

16. 5) Type - CE 4 :
 Inactive.
 degenerative
contents.
 no daughter cysts.
 not fertile.

17. 6) Type - CE 5 :
 Inactive.
 thick calcified wall.
 not fertile.

18. WHO-IWGE USG classification
:
IWGE : informal Working Group on Echinococcosis
• Group 1 : Active-cyst >2 cm; fertile.
• Group 2 : Transitional group - may contain viable scolices.
• Group 3 : Inactive - degenerated, calcified, non viable cyst.

19. Thank you …