1. HYDATID CYST: Gharbi et al. (1981)
Type I: simple cyst.
Type II: “water lily“ sign.
Type III: daughter cyst/s.
Type IV: “solid“ mass.
Type V: calcification.

2. TYPE I: SIMPLE CYST Early stage of the disease: unilocular cyst.
Differencial diagnosis: simple cyst, abscess (bacterial, amebic), hematoma and necrotic hepatocelular carcinoma.
The differential diagnosis from a simple cyst with imaging criteria alone sometimes is difficult and can only be made when laboratory analysis and a history of living in endemic regions are taken into consideration.

3. TYPE I: SIMPLE CYST
US: anechoic lesion with/without sand and/or septa. Rolling the patient during evaluation disperses the sand, creating small echogenic foci called “falling snowflakes.”

4. TYPE I: SIMPLE CYST
CT: water-attenuation mass. The septa and cyst wall may enhance after injection of contrast material.

5. TYPE I: SIMPLE CYST
MRI: hypointensity on T1-weighted images and hyperintensity on T2-weighted images (red arrow). A low-signal-intensity rim (parasitic membranes and perycist) has been described as characteristic of HD. However, it is a nonspecific finding that can also be seen in amebic abscess, hepatocellular carcinoma and hematoma.

6. TYPE II: “water lily” sign
PATHOGNOMONIC of HD: cyst with separation of the membrane (red arrow) or collapsed cyst wall due to contained rupture of the HC.

7. TYPE III: CYST with DAUGHTER CYST(s)
Daughter cysts or vesicles can be seen in the cyst (fig. A). Multiple cysts that are enclosed together within a single capsule give rise to a “racemose” or “wheel spoke” appearance (fig. B and C). B A C

8. TYPE III: CYST with DAUGHTER CYST(s)
MRI: daughter cysts may appear hypointense or isointense relative to the maternal matrix on T1- and T2-weighted images. The “serpent or snake sign” represents collapsed parasitic membranes (membranes have low signal intensity with all sequences).
Axial phase/op-phase
T1-weighted images
Axial T2-weighted image

9. TYPE IV: “SOLID” MASS A B
US (fig. A) shows a “solid” liver mass. At CT (fig. B) the lesion shows
fluid attenuation, with peripherial rim calcification. The “solid” aspect at US
may be due to high protein components in the cyst.

10. TYPE V: CALCIFIED CYST Last stage of the disease. 20-30 % of HC.
Parcial: curvilinear or ring-like pattern (calcification of the pericyst).
Total: dead cyst.
Internal calcification in the matrix may also be seen.
Total/internal calcification
Curvilinear calcification

11. TYPE V: CALCIFIED CYST Rim calcification Total calcification
Internal calcification