Crossed ectopic left lung with fusion to the right lung : A variant of horseshoe lung?

A 9-year-old boy presented with the chief complaint of exercise intolerance. Breath sounds were diminished over the left hemithorax. Frontal and lateral chest radiography showed opacilication of the left hemithorax because of the deviated heart and mediastinum(Fig. IA). Echocardiography and main pulmonary artery angiography showed two vessels arising from the main pulmonary artery. turning tO the right in parallel. and extending across the midline to the right hemithorax (Fig. 1B. No other intracardiac anomaly was found. c-F scans of the heart were obtained on a CI 50L Ultrahist CT scanner ( Imatron. South San Francisco. CA) with electrocardiographic gating; nonionic iodinated contrast medium (contaming 37 g of iodine per 100 ml (iopromide lUltravist 370: Schering. Berlin. Germanyl was administered. The slice thickness was 3 mm. Two vessels of nearly equal size arose from the main pulnionary artery running to the right. The anterior branch followed the normal course for the right pulmonary artery. The posterior branch coursed horizontally to the right side behind the carina (Fig. IC). The left atrium was elongated transversely. The right pulmonary veins drained in their usual pattern. An anomabus pulnionary vein froiii the ectopic lung drained into the left atrium in the right paramidline of the thorax. Another CT scan. within one breath-hold. was performed a I#{232}wdays later with coronal retonnation of the airway. The right lung had three lobes with a normal trifurcated right main bronchus. Additional pulnionary parenchyii a was located in the lower posterior thorax and had its own sharply tapering left niain bronchus in the midline ofthe thorax. This pulmonary segnient straddled the spine between the heart and the esophagus. Fusion ot this segI1 ent with the right lower lobe was recognized as a well-demarcated pleural line on CT images.