Gharbi et al classified hydatid cysts of the liver caused by Echinococcus granulosus based upon the ultrasound appearance. The authors are from National Institute of Childhood Health in Tunisia.
Features allowing diagnosis of hydatid cysts on ultrasound:
(1) variable appearance from one section to another in the same area
(2) hyperechoic contour with possible areas of acoustic shadow
(3) presence of small fluid collections from intra- and extra-cystic secondary vesicles ("daughter cysts")
(4) presence of another cyst at a different stage of evolution
|
Type |
Description |
Features |
|
I |
pure fluid collection |
anechoic space with marked enhancement of back-wall echoes; fluid filled with well-defined borders; wall will show a localized thickening; if small may appear punched out without a proper wall |
|
II |
fluid collection with a split wall |
well-defined border but less round and may appear to "sag"; split wall may be just outside the cyst or appear as a floating membrane within the cyst |
|
III |
fluid collection with septa |
well-defined border divided by septa with "honeycomb" |
|
IV |
heterogeneous echo patterns |
see below |
|
V |
reflecting thick walls |
very hyperechoic contour with a cone-shaped shadow |
|
other |
shell-cyst |
very hyperechoic and usually calcified to some degree |
|
Subtype of Type IV |
Features |
|
IVA |
hypoechoic with a few irregular echoes, associated with an infected multi-locular cyst |
|
IVB |
hyperechoic, solid pattern without back wall shadow |
|
IVC |
intermediate between hyper- and hypo-echoic |
Frequency of patterns:
(1) Type I is most common
(2) Types II, III and IV are less frequent
(3) Type V is very rare
Specialty: Infectious Diseases
