Rare variant of total anomalous pulmonary venous connection: intrapulmonary drainage of one lung by the other--a case report and review of the literature.

Total anomalous pulmonary venous connection is an uncommon congenital cardiovascular anomaly but one that occurs frequently in the asplenia syndrome. We present a rare type of total anomalous pulmonary venous connection in a 4-month-old baby with the asplenia syndrome. In this patient, all of the left pulmonary veins united to form a common pulmonary vein, which crossed the mediastinum and then proceeded in an intrapulmonary fashion in the right lung. A small pulmonary vein emerged from the right upper lobe and drained into the right superior vena cava. Nine other cases have been reported, four also with asplenia, five with otherwise normal cardiac anatomy apart from an atrial septal defect. The incidence of pulmonary venous obstruction is high, at least 70%. Two cases, both with a normal heart, had corrective surgery. One with no pulmonary venous obstruction was repaired successfully. Embryologically, this type of total anomalous pulmonary venous connection represents a developmental error early in embryonic development before the venous connection between the two lungs and the cardinal veins involute.