Unilocular hepatic echinococcal cysts: sonography and computed tomography findings

In endemic regions, unilocular hepatic echinococcal cysts (HEC) may be difficult to differentiate radiologically from simple non-parasitic cysts, especially if serological tests were negative. The aim of this descriptive study is to elucidate distinctive imaging findings that allow a diagnosis of HEC.

The sonographic and computed tomography (CT) findings of 21 patients with proven unilocular HEC were retrospectively analysed. A total of 28 examinations were reviewed, including 14 sonograms (ultrasound; US) of the liver and 14 CT studies.

Seven imaging features that help in the diagnosis of unilocular HEC were identified by US and/or CT in 14 patients (14/21; 66.6%). They are, by order of frequency: hydatid sand (29.2%), focal or segmental thickening of the cyst wall (29.2%), coexistent echinococcal cysts in the spleen or lungs (16.6%), pericystic biliary radicles dilatation (8.3%), atrophy of the right lobe with compensatory hypertrophy of the left hepatic lobe (8.3%), satellite cysts typical of HEC in the liver (4.2%) and pericyst calcification (4.2%).

These ancillary signs should prompt us to consider HEC as the cause of a unilocular cyst in approximately two-thirds of patients.