A case diagnosed with neonatal mediastinal cyst after management as isolated pericardial effusion in pregnancy

Abstract

A hypoechoic free space around the fetal heart can be differentiated with ultrasonography as pericardial effusion or a mediastinal cyst. Respiratory or circulatory failure may occur if the space becomes so enlarged as to put pressure on the heart and lungs. We report a case diagnosed with a neonatal mediastinal cyst after management as isolated pericardial effusion in pregnancy. The patient was 27 years old (para 1). A hypoechoic free space with a width of 2 mm around the left ventricle was detected on fetal ultrasonography at 30 weeks of gestation. The case was diagnosed as isolated pericardial effusion not complicated by fetal structural abnormalities or hydrops. Nevertheless, the hypoechoic area increased in size to 15 mm at 36 weeks of gestation, pressing on the left ventricle and the left lung; thus, a caesarean section was performed at 37 weeks and 2 days of gestation, while preparing for emergency pericardiocentesis. The neonate was stable with intubation, and a neonatal ultrasonographic examination showed the cystic lesion, which was recognized as fetal pericardial effusion; therefore, pericardiocentesis was not performed. A chest MRI diagnosed the mediastinal cyst 3 days after birth. The size of the cyst was unchanged, with no symptoms for 10 months. If a hypoechoic free space around the fetal heart is detected, we should carefully make the diagnosis, including mediastinal cyst in addition to pericardial effusion in the differential diagnosis.