An 81-year-old woman with a history of diabetes mellitus and angina underwent chest CT after an abnormal chest radiograph suggesting a right pulmonary vascular abnormality. She had no respiratory symptoms, and transthoracic echocardiography showed no evidence of pulmonary hypertension or right heart strain.

Three-dimensional reconstructed CT images demonstrated absence of the right upper lobe bronchus and the corresponding pulmonary artery, consistent with right upper lobe agenesis, with associated pulmonary venous abnormalities of the right lung (figure 1A–C). Most of the right lung drained through a dominant pulmonary vein into the left atrium, whereas a slender accessory pulmonary vein arising from the middle and lower lobes drained into the inferior vena cava (figure 1C). No anomalous systemic arterial supply from the descending thoracic aorta was identified on contrast-enhanced CT. Recognition of the anomalous pulmonary venous drainage prompted further detailed evaluation of the right lung anatomy. A sagittal 3D…