Figure 5b. Horseshoe lung in a male neonate. (a) Axial CT scan obtained at the level of the lung bases shows an isthmus of pulmonary parenchyma (arrow) that extends behind the heart and joins the posterobasal segments of both lungs. An anomalous right pulmonary vein (*) drains into the IVC. (b) Volume-rendered reformatted image of the airways and lung parenchyma reveals partial fusion of the lungs posterior to the heart and an abnormal bronchus that arises from the left main bronchus and crosses the thoracic midline. (c) Coronal multiplanar reformatted image shows an anomalous right pulmonary vein (*) that drains into the IVC below the level of the right hemidiaphragm. (d) SSD reformatted image of the pulmonary artery demonstrates an inferior branch (*) that arises from the right pulmonary artery (•) and crosses the midline to the base of the left lung. (e) Anteroposterior arterial phase pulmonary angiogram helps confirm the CT angiographic findings. * = anomalous branch, • = right pulmonary artery.