Potential direct communication of the lung to the mediastinum: computed tomographic evaluation of pulmonary venous connections.

Purpose: We hypothesized that the remnant of the primitive pulmonary venous plexus in the embryo provides a pathway for direct communication from each lobe of the lung to the mediastinum. We assessed the presence and location of these connections by using 64-row multidetector computed tomography (CT).
Materials and Methods: This study was approved by the institutional ethics committee. First, we analyzed the multidetector row CT images of 120 normal lungs for the presence of septal structures between the pulmonary veins and the mediastinum and the extension of mediastinal fat into these septal structures. Second, we analyzed 62 patients with pneumothorax for the presence of cross-bridging structures in the pleural cavities.
Results: We frequently observed septal structures (36% to 77%) and the extension of mediastinal fat (8% to 56%) in the right apical segment, left apical posterior segment, both right and left anterior segments, right medial segment, and left inferior lingular segment. Cross-bridging structures were observed in 44% of right and 38% of left pneumothoraces and were noted in the right apical and posterior segments, left apical posterior segment, both anterior segments, right middle lobe, and left lingular segments. Septal and cross-bridging structures both showed a similar distribution pattern.
Conclusions: Venous septal structures in normal lungs and cross-bridging structures in pneumothoraces visualized on CT images suggest the presence of direct pathways from each lobe of the lung to the mediastinum.