Presentation
Referred to the Emergency Department for a FAST scan after sustaining blunt abdominal trauma. Otherwise asymptomatic.
Patient Data
![](https://prod-images-static.radiopaedia.org/images/14157516/b4c6585ecb63d1553bf8b015f58917_thumb.jpg)
![](https://prod-images-static.radiopaedia.org/images/14157524/ba0e025ee4f707cf85f036316a02d4_thumb.jpg)
![](https://prod-images-static.radiopaedia.org/images/14157532/df7fbefe5a28a36aa28d5a55c196b4_thumb.jpg)
![](https://prod-images-static.radiopaedia.org/images/14157539/3320eea40954400b3d551527337a84_thumb.jpg)
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![](https://prod-images-static.radiopaedia.org/images/14157516/b4c6585ecb63d1553bf8b015f58917_big_gallery.jpg)
A well-defined cystic lesion measuring 8.0 x 6.5 x 7.4 cm in the right lobe of the liver (segment 7 and 8) with low-level internal echoes. The cyst shows a detached, irregular laminated membrane inside it which appears to float within the contents of the cyst.
Rest of the study is unremarkable.
Case Discussion
The findings are suggestive of a hepatic hydatid cyst with ultrasound "water lily sign". According to the WHO classification of hepatic hydatid cysts, the water lily sign is seen in stage CE3a, which represents a transitional stage between active and inactive disease. The mechanism of detachment of membrane is related to decreased intracystic pressure, degeneration, host response, trauma or following therapy.