Presentation
Right upper quadrant pain in a child of rural origin.
Patient Data
Well-defined cystic lesion in the right lobe of the liver measuring 78 x 68 x 65 mm with detached, irregular laminated membranes floating within the content.
Minute amount of free fluid in right corner of the paravesical fossa.
The urinary bladder is markedly distended.
The rest of the abdominopelvic CT is unremarkable.
Case Discussion
The CT features are most consistent with a hepatic hydatid cyst with "water lily sign".
According to the WHO classification of hepatic hydatid cysts, the water lily sign is seen in stage CE3a. It 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. The detachment of the endocyst membrane results in floating membranes within the pericyst that mimic the appearance of a water lily.
It is classically described on plain radiographs but may be seen on ultrasound, CT, and MRI.