Embryology of PAPVR. (A) At post-conceptional Days 27 29, the primordial lung buds drain through a vascular bed to the cardinal veins, which will develop into systemic veins. (B) By Days 32 33, the common pulmonary vein forms from the left atrium and establishes a connection with the pulmonary venous circulation. Pulmonary venous connections to systemic veins begin to regress and pulmonary venous blood drains into the common pulmonary vein. (C) By Day 40, the primitive connections from the pulmonary vascular bed to the cardinal veins should have regressed, but in PAPVR anomalous connections persist. (D) At term, the anomalous connection will have developed into anomalous pulmonary veins draining most commonly into the SVC on the right, or the brachiocephalic vein on the left.
Additional keywords: embryology,PAPVR,pulmonary venous return,anomalous,