Unexplained Hypoxemia in School-Age Child: Do Not Forget the Double Superior Vena Cava.

Persistent left superior vena cava (SVC) is a rare congenital malformation of the thoracic venous system. We report a case involving a 7-year-old boy, who was admitted to our CT scanning room because of an incidental discovery of low blood-oxygen levels (90-94% in good health). A persistent left SVC was depicted, with drainage in the left atrium and a resultant right-to-left shunt;right SVC was present, draining to the right atrium.