Ans. B. Hydatid cystThe Portal phase CT demonstrates a large cystic structure with a discrete wall, separated internal membranes and several 'daughter cysts'This is an infection of the liver with Echinococcus granulosus, a parasitic tapeworm presents worldwide and transmitted from sheep, foxes and other wild animals to humans as part of its lifecycle. Larvae migrate from the gut and embed in the liver, where they encyst and develop, slowly provoking a surrounding inflammatory reaction. The disease may remain occult for several years. On imaging there is a wide range of appearances, from a simple cyst indistinguishable from a true hepatic cyst to a complicated cyst with any or all of the following features: debris (hydatid 'sand" made up of dead scolices, which may calcify), daughter cysts, membrane separation, and wall calcification. The lesions may be multiple and vary widely in size. Serological testing can be employed to confirm the presence of infection prior to any therapy or intervention. Although the risk of anaphylaxis following aspiration or surgery of these lesions is well recognized, it is less than previously thought, and uncomplicated aspiration following medical treatment has been described.US demonstrates clearly not only the simple cyst form but also the more complex cyst features, such as the dependent debris, daughter cysts (cyst within a cyst appearance), membrane separation and wall calcification. CT defines all these features as well and is helpful where wall calcification obscures the view on US. MRI will define the cystic structure and internal anatomy but is insensitive to the calcification.