Sonographic features of parovarian cysts.

Parovarian cysts are responsible for about 10% of all adnexal masses. They arise from the tissues of the broad ligament, predominantly from mesothelium covering the peritoneum but also from paramesonephric and mesonephric remnants. When large, they become symptomatic due to pressure effect. Clinically it is difficult to distinguish an ovarian mass from one arising in the parovarium. A series of eight surgically and pathologically proven parovarian cysts is presented. All were symptomatic and most were palpable. Sonographically they were thin-walled, smoothly marginated, unilocular cysts. Six of the eight were located superior to the fundus of the uterus. Parovarian cysts should be included in the differential diagnosis along with large physiologic ovarian cysts and unilocular ovarian cystadenoma when a mass with the above sonographic features is demonstrated.