"Congealed waterlilly" sign: a new sonographic sign of liver hydatid cyst.

The ultrasonographic (US) appearance of hydatid liver disease is well established, but solid cysts have long defied US characterization. We present 23 solid cysts and describe a new feature called the "Congealed waterlilly" sign. As the physical characteristics of the hydatid fluid change from watery to a viscid gel, it becomes echogenic. The intact folds of the germinal layer trapped within the viscid matrix give rise to the appearance of curvilinear structures which no longer move with changing patient posture. Similar findings have been observed in eight medically treated patients. We observed progression from an initial simple cyst to a "floating waterlilly" through to a "congealed waterlilly" in treated patients. The final appearance was indistinguishable from the untreated solid cysts. The congealed waterlilly sign is reliable and strongly suggestive of hydatid cysts.