Horseshoe lung associated with scimitar syndrome.

Horseshoe lung is a rare congenital anomaly and mostly accompanied by scimitar syndrome. Most aspects of this complex anomaly can be demonstrated via multidetector CT (MDCT). We present two baby girls who had horseshoe lung associated with right lung hypoplasia and scimitar vein. The chest roentgenograms showed displacement of the heart and mediastinum to the right with smaller right lung. Echocardiography revealed dextroposition, secundum atrial septal defect and bilateral slight peripheral pulmonary stenosis in the first case and dextroposition, severe pulmonary hypertension, secundum atrial septal defect and tricuspid regurgitation in the other one. On thoracic MDCT, the right lung and pulmonary artery were hypoplastic with cardiomediastinal shift to the right. There was an abnormal right pulmonary vein draining into the inferior vena cava on the lower zone of the right lung (scimitar vein). The posterobasal portions of the both lungs were fused through a midline isthmus behind the heart.