Absent right and persistent left superior vena cava: fetal and neonatal echocardiographic diagnosis.

Absence of the right superior vena cava (SVC) is a rare event occurring in patients without congenital cardiovascular abnormalities. Since absence of the right SVC is usually clinically silent, its diagnosis is mandatory prior to invasive medical or surgical procedures. We report two cases of echocardiographic diagnosis of absence of the right SVC with persistent left SVC and a large coronary sinus in structurally normal heart in a fetus of 20 weeks' gestation and in a newborn. The diagnosis was confirmed by transthoracic contrast echocardiography with intravenous injection of agitated saline into the right arm.