Partial anomalous pulmonary venous drainage of the left upper lobe vs duplication of the superior vena cava: distinction based on CT findings.

Abstract

Partial anomalous pulmonary venous drainage of the left upper lobe and duplication of the superior vena cava have similar appearances on CT scans. The purpose of this study was to review their appearances and provide guidelines for differentiating between them. A review of the CT reports for the preceding 4 years disclosed seven patients whose original diagnosis was duplication of the superior vena cava and one patient whose diagnosis was partial anomalous pulmonary venous drainage of the left upper lobe. The 14 CT examinations of these eight patients were reviewed in order to observe the CT findings in each anomaly. In only five of the seven patients whose original diagnosis was duplication of the superior vena cava were CT findings compatible with that diagnosis. In the other two, CT findings were compatible with partial anomalous pulmonary venous drainage of the left upper lobe, as they were in the one patient with that as his original diagnosis. Two CT findings allow consistent differentiation. In duplication of the superior vena cava, two vessels can be seen anterior to the left main bronchus, whereas no vessels are present in this location in partial anomalous pulmonary venous drainage of the left upper lobe. Additionally, careful inspection reveals that the intraparenchymal veins in the left upper lobe drain to the normally positioned left superior pulmonary vein in duplication of the superior vena cava, whereas they drain to the anomalous vessel in partial anomalous pulmonary venous drainage of the left upper lobe. Careful analysis of the CT scans with particular attention to these two features allows differentiation between partial anomalous pulmonary venous drainage of the left upper lobe and duplication of the superior vena cava.