Classify the cyst by the WHO-IWGE ultrasound stage (CE1–CE5) — it decides active versus inactive and treatment — and look for rupture into the biliary tree, which changes management.
Orient first
- CE1: unilocular with a double wall; CE2: multiseptate daughter cysts (honeycomb); CE3a: detached membranes (water-lily); CE3b: daughter cysts in a solid matrix; CE4: heterogeneous solid (ball of wool); CE5: calcified wall (verify the classification version).
- CE1–CE2 are active, CE3 transitional, CE4–CE5 inactive.
- Biliary communication (cystobiliary fistula) causes cholangitis and jaundice.
Acquire the study
- Curvilinear probe; position changes to move membranes and sand.
The manoeuvre
- Cyst wall: double-line sign (CE1).
- Internal content: hydatid sand (falling snowflakes with position change), daughter cysts, floating membranes.
- Assign the WHO-IWGE stage and measure the cyst in cm.
- Dilated ducts or echogenic material in the CBD — rupture into the biliary tree.
What confirms it
- Pathognomonic features (double wall, daughter cysts, detached membranes) with serology in an endemic context.
What licenses you to exclude it
- A truly simple cyst without a double wall, sand or membranes on high-resolution ultrasound is not hydatid.
The classic misread
- CE1 is easily called a simple cyst — look for the double wall and sand.