What is scimitar syndrome, and what are its associated imaging findings?
Scimitar syndrome, or hypogenetic lung or pulmonary venolobar syndrome, is a rare disorder characterized by a hypoplastic lung (almost exclusively on the right) in association with an anomalous pulmonary vein. This anomalous pulmonary vein can drain into many structures, including the infradiaphragmatic inferior vena cava (IVC), suprahepatic IVC, portal vein, or right atrium. The chest radiograph typically shows a small right lung with a curvilinear tubular opacity paralleling the right heart border (the “scimitar” sign) due to an anomalous right pulmonary vein. Cardiac dextroposition, pulmonary artery hypoplasia/aplasia, or systemic arterial collateral supply to the ipsilateral lung may also be seen. On CT and MRI, the course and anatomy of the anomalous vasculature can be well visualized.