Echinococcus granulosus is the most common cause of hydatid disease.

This ultrasonographic sign is pathognomonic for Echinococcus hydatid cyst in the transitional stage (WHO CE3). It is necessary to recognize and diagnose the exact stage of echinococcus cyst, because the PAIR (Puncture, Aspiration, Injection, Re-aspiration), a minimally invasive therapeutic option is feasible in types CE1, CE2 and CE3 of the WHO classification of Echinococcus cysts.