Radiographic Features of the Scimitar Syndrome

Abstract

The scimitar syndrome is a rare but nevertheless important developmental cardiopulmonary abnormality of particular interest to the radiologist because it can be readily recognized on plain roentgenograms. In view of the fact that only 54 cases have been reported in the world literature (1) and 7 patients with this malformation have been studied at the University of Minnesota Heart Hospital, it is appropriate to summarize the radiographic features. The full-blown syndrome, which invariably involves the right lung and its vascular supply, consists of: (a) hypoplasia of the right lung with subsequent dextroposition of the heart into the right thoracic cavity; (b) hypoplasia of the right pulmonary artery; (c) anomalous arterial supply from the abdominal aorta to the right lower lobe; (d), most important of all, anomalous venous drainage of the right lung by a large vein emptying into the inferior vena cava just below or above the right hemidiaphragm (2–5). The clinical features vary considerably with the degree of associated lung hypoplasia which results in repeated respiratory infections. Recurrent bouts of pneumonitis may be the dominant symptom, especially in the pediatric age group (1). On the other hand, in the milder form without significant lung hypoplasia, the abnormality may be discovered as an incidental finding on a chest film. Associated cardiac abnormalities have been rarely reported in the literature, but such intracardiac malformations were encountered in 3 of our patients. Two had ventricular septal defects with pulmonary stenosis, and one had a reversing patent ductus arteriosus (1). Discussion of Radiographic Features Plain Roentgenograms of the Chest: In patients with significant hypoplasia of the right lung, the postero-anterior roentgenogram may show a slightly smaller right bony hemithorax with a generalized shift of the mediastinal structures to the right (6–8) (Fig. 1). Frequently, the right heart border is indistinct (Fig. 1), apparently because of commonly found pleuropericardial adhesions and atelectasis secondary to repeated episodes of pulmonary infection. Pleural changes may be well visualized on the lateral film study, causing indistinctness of the right diaphragmatic contour (Fig. 2). Either the entire right lung may be drained anomalously or only the middle or lower lobes (5, 8). Characteristically, the anomalous vein shows a vertical course toward the right cardiophrenic angle, closely paralleling the right atrium. Due to its gentle curvature, the vein appears quite similar to a curved Moslem sword or scimitar (9). Depending upon the degree of right pulmonary hypoplasia, the vein may project through the right heart or in the right pericardial area. In all our observed cases, the scimitar vein was clearly visible on plain roentgenograms of the chest without laminagraphy, a procedure necessary only in doubtful cases.