Hepatic echinococcal cysts: sonographic appearance and classification.

The sonographic appearance of echinococcal lesions of the liver was studied in 59 patients. We have proposed a classification of these lesions that reflects the pathology and natural history of the disease: type I, simple fluid-filled cysts; type IR, lesions containing undulated membranes that represent detached endocyst secondary to rupture; type II, lesions that contain daughter cysts and/or a formed echogenic material we call matrix; and type III, dead, densely calcified lesions. The natural progression of hepatic echinococcal cysts is from type I to type III. Daughter cyst formation is part of the natural aging process. When hydatid cysts are infected, they lose their characteristic sonographic appearance and become diffusely hyperechoic.