Total anomalous pulmonary venous return (TAPVR) occurs when all pulmonary veins fail to drain into the left atrium. Instead, all pulmonary veins drain anomalously into the systemic venous tributaries or into the right atrium. An interatrial communication (right-to-left shunt), either an atrial septal defect (ASD) or patent foramen ovale (PFO), is necessary for survival.

Depending on the drainage site of the pulmonary veins, the anomaly may be divided into the four types. The current case represents type III (infracardiac or infradiaphragmatic), which accounts for 13% of TAPVR cases. The common pulmonary venous sinus drains to the portal vein, ductus venosus, hepatic vein, or inferior vena cava (IVC).  The common pulmonary vein penetrates the diaphragm through the esophageal hiatus.  This type is virtually always accompanied by some degree of obstructed venous return.