ULTRASOUND IN HYDATID DISEASE

ULTRASOUND IN HYDATID DISEASE

Hydatid cyst is caused by  Echinococcus infection , resulting in cyst formation anywhere in the body. Humans are accidental host and the infection occurs by ingesting food contaminated with Echinococcus eggs.

Site preference -

•  Liver – commonest
•  Lung -  2^nd commonest
•  Spleen
•  Central nervous system
•  Retroperitoneal
•  Musculoskeletal organs

Two main strains -

1.  Echinococcus granulosus:  common
2. Echinococcus alveolaris/multilocularis: less common but more invasive

The cysts usually have three components:

·   pericyst:  usually made up of inflammatory tissue of host origin

·   exocyst

·   endocyst: scolices (the larval stage of the parasite) and the laminated membrane  

The world health organization 2001 classification of hepatic hydatid cysts 

 CL - Unilocular anechoic cystic lesion without any internal echoes and septations

CE 1 -Uniformly anechoic cyst with fine echoes settled in it representing hydatid sand

CE 2 -Cyst with multiple septations giving it multivesicular appearance or rossette appearance

          or honey comb appearance with unilocular mother cyst . This stage is the active stage .

CE 3 - Unilocular cyst with daughter cysts with detached laminated membranes appearing as water

            lily sign , & this is the transitional stage of the cyst .

CE 4 - Mixed hypo and hyperechoic contents with absent daughter cysts, these contents give an

           appearance of ball of wool sign indicating the degenerative nature of the cyst .

CE 5 -Arch like thick partially or completely calcified wall , & this stage of cyst is inactive and

          infertile.

Morphological classification of cysts

Type I: simple cyst with no internal echos or  architecture

Type II: cyst with daughter cyst(s) + matrix echos

Type IIa: round daughter cysts at periphery

Type IIb: larger, irregularly shaped daughter cysts occupying entire volume of the mother                                   cyst

Type IIc: oval masses with scattered calcifications and occasional daughter cysts

Type III: calcified cyst (dead cyst)
Type IV: complicated cyst, e.g. ruptured cyst

IMAGE PRESENTATIONS

Case 1-Simple type 1 (morphological), CLtype (WHO), Active Hydatid Cyst

Fig 1-Hepatic sonogram shows a large well defined unilocular cystic mass in right lobe.The wall of the mass is smooth regular and slightly echogenic.This is a unilocular Simple Type 1  active Hydatid Cyst.

Fig 2- High Resolution hepatic sonogram reveals classical double echogenic layered appearance indicating inner endocyst and outer ectocyst (arrows).

  

 Fig 3- Axial CT scan image showes a large well defined unilocular rounded hypodense non enhancing mass in right lobe liver with fluid density.

 Fig 4-Coronal reconstruction CT image of the same case.

 Fig 5- Per operative photograph of the same case shows underlying cyst with bulging hepatic contour. 

 Fig 6-Per op photograph shows exposed interior of the cyst after incision and deflation.

 Fig 7-Shows removal of endocyst.

Fig 8- Gross Specimen of removed endocyst. 

Case 2- Type 2a (morphological), CE 2 (WHO), Active Cyst

Fig 9- Hepatic sonogram shows large hydatid cyst with multiple peripheral daughter cysts and central echogenic matrix- Spoke Wheel appearance

Case 3- Type 2b (morphological), CE 2 (WHO), Active Cyst

Fig 10- TVS pelvic scan shows large multiloculated adnexal mass with Honey Comb appearance.In this case mother cyst is full of multiple small daughter cysts. As both ovaries were seen separate and normal, the diagnosis of adnexal (likely broad ligament) pelvic hydatid cyst was made.

Fig 11- Post operative specimens of the above pelvic adnexal hydatid cyst case proved to be broad ligament hydatid cyst (one of the rare entity). Gross specimens showing ectocyst (red piece), endocyst (white piece) and kidney tray containing daughter cysts. 

Fig 12- Hepatic sonogram shows a large rounded complex cystic mass in left lobe with Honey Comb appearance.

Fig 13-Hepatic sonogram shows a large complex cystic mass with multiple small daughter cysts see as mobile sediments, likely suggests detached daughter cysts.

Case 4 -  CE 3 (WHO) type transitional stage hydatid cyst
.

Fig 14- Hepatic sonogram shows large complex cystic mass right lobe with detached endocyst layer appearing as echogenic curvilinear structure.

Fig 15- Hepatic sonogram of another case shows collapsed hydatid cyst with detached undulated endocyst.

Case 4- CE 4 type collapsed consolidating (solid appearing) inactive hydatid cyst.

Fig 16- Hepatic sonogram shows large rounded hyper echoic solid appearing mass with multiple hypoechoic curvilinear echos clustered within mass without daughter cysts. It is suggestive of consolidating inactive hydatid cyst.

Case 5 - Type 3 (morphological), CE 5 (WHO) type collapsed consolidating (solid appearing) inactive hydatid cyst.

Fig 17- Hepatic sonogram shows a well defined rounded mass with echogenic rim calcification casting distal shadowing. Here the lesion is inactive and infertile with calcifying nature.

Case 6 - Type 4 (morphological) Complicated hydatid cyst.

Fig 18- Hepatic Sonogram shows complex cystic mass left lobe liver full of internal echos and multiple bright foci with dirty down shadowing,suggestive of air. The case was earlier diagnosed as simple type hydatid cyst, which at present appears complicated by air and infection.

P.S.-This presentation is intended for medical professionals and imaging specialists for                       academic purposes. It needs discussion and further review of literature.
           - My special thanks to Dr.Gaurav Bahety M.Ch. (Ped. Surgeon) and Dr.S P Sharma                      (Gen.Surgeon) for operative feedback, and Dr.Kartikeya Nathiya, Bhilwara, for article                layout and crafting.

References

1] For more detail study – ref.  http://radiopaedia.org/articles/world-health-organization-2001-classification-of-hepatic-hydatid-cysts