A 6-year-old girl presented to the emergency department with abdominal pain for 3 days.
Axial and coronal sections (Figure1a and 1b) of the contrast-enhanced computed tomography (CT) image reveals the presence of cystic attenuating hypodense lesion in the right lobe of liver with crumpled up laminated membranes within the lesion.
Hydatid disease is caused by echinococcus species. Humans get the infection by eating contaminated food and drinking contaminated water. Hydatid cyst has three layers:1) an outer pericyst composed of a dense fibrous capsule; 2) a middle layer of laminated membrane; and 3) innermost endocyst. 
The clinical presentation of the disease varies according to the site involved. For hepatic hydatid, it may be presented as hepatomegaly or as jaundice.  Imaging tools are needed to diagnose the disease and to know the extent of involvement. Prior knowledge of the organs which are involved and morphological details along with associated complications are helpful in planning the treatment.
The various imaging modalities used for diagnosis are ultrasonography, CT and magnetic resonance imaging. A few of the signs like snowstorm sign, honeycomb appearance, spoke wheel appearance and water-lily sign are characteristic for the disease and help in diagnosis. 
The completely detached undulating membrane inside a hypodense cystic lesion is called water-lily sign, which was seen in our case. The final diagnosis is made by a combination of imaging studies, serological markers and immunologic studies. 
One has various options for treating hepatic hydatid, such as as medical management, surgical therapy or percutaneous drainage techniques and combined approach. 
The water-lily sign in the echinococcal disease is so characteristic that if present, diagnosis can be made solely on imaging features.
Written informed patient consent for publication has been obtained.
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