We describe an adult female presenting with dyspnea in whom both transthoracic and transesophageal echocardiography detected a mobile sac-like structure in the right ventricular outflow tract (RVOT) containing a heterogenous echogenic mass. This sac-like structure markedly changed its shape and size during the cardiac cycle. These findings and the fact that the patient lived in a rural area raised the possibility that this was a hydatid cyst. A bubble study using normal saline was useful in detecting a contained rupture of the cyst. Bubble echoes were noted within the sac-like structure but did not penetrate the inner wall of the cyst which contained echogenic material, indicating that the rupture was confined only to the outer layers. At surgery, a 0.5 cm communication was noted between the cyst and the RVOT and pathology confirmed the diagnosis of hydatid cyst.
