Sonographic spectrum of hydatid disease.

Hydatid disease, caused by Echinococcus granulosus, is a parasitic disease that is endemic in many parts of the world. Hydatid cyst demonstrates a variety of imaging features, varying according to growth stage, associated complications, and affected tissue. The radiologic findings range from purely cystic lesions to a completely solid appearance. Ultrasound is the most important imaging modality for liver hydatid disease and clearly demonstrates the floating membranes, daughter cysts, and hydatid sand characteristically seen in purely cystic lesions. The radiologist's familiarity with the imaging findings of the disease is very important for earlier diagnosis and an appropriate treatment. There are several classification schemes for liver hydatid cysts based on their ultrasound appearances; the initial classification by Gharbi et al and the World Health Organization classification are the most commonly preferred. Computed tomography and magnetic resonance imaging play a key role in recognizing the complications such as rupture and infection of cysts associated with hydatid disease. Today, percutaneous treatment of liver hydatid cysts, a safe, easily applicable, and well-tolerated method, has become the most effective and reliable treatment procedure in most cases if the hydatid cyst is viable. In patients treated with the percutaneous treatment technique, a decrease in the dimensions of the cyst, solidification of the cyst contents, and irregularity in the walls of cysts are signs suggestive of cure. The radiologist should also be familiar with the postoperative follow-up ultrasound findings of hydatid cyst to prevent misinterpretation of the hypoechoic, anechoic, or hyperechoic appearance of posttreatment hydatid disease appearance as recurrence.