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In lobectomy, it is important to isolate and transect the supplying structures belonging to the respective lobe. In the middle lobe lobectomy, these are the middle lobe vein (V4+V5), the middle lobe artery (A4+A5), and the middle lobe bronchus (B4+B5).
- Bronchus: The middle lobe bronchus is approximately 2.5 cm long and originates about 3 cm below the upper lobe bronchus opposite the B6 bronchus. It runs obliquely ventrocaudally and then divides into the lateral B4 and medial B5 segmental bronchus.
- Artery: The middle lobe artery arises from the anterior side of the interlobar part of the pulmonary artery. A common middle lobe artery occurs about as frequently as separate A4 and A5 branches, which branch off from the pulmonary artery about 5-10 mm apart.
- Vein: The segmental veins V4 and V5 drain blood through a common trunk into the superior pulmonary vein. In 10% of cases, however, the middle lobe vein drains into the inferior pulmonary vein. Occasionally, the segmental veins V4 and V5 drain into the superior pulmonary vein without a common trunk.