(1)
IMM, Curie-Montsouris Thorax Institute, Paris, France
9.1 Anatomical Landmarks
Bronchus
As it enters the parenchyma, the upper lobe bronchus triplicates into three segmental bronchi: apical (B1), posterior (B2), and anterior (B3). B1 and B2 can originate separately or as a common trunk (B1+2) (◘ Fig. 9.1a).
Fig. 9.1
Anatomical landmarks. a segmental bronchus (posterior view), b arterial supply to the posterior segment (posterior view), c venous drainage (anterior view)
Arteries
The posterior segment is supplied by the ascending A2 (Asc.A2) that originates within the fissure from the posterior aspect of the pulmonary artery, opposite the middle lobe artery (◘ Fig. 9.1b). It ascends to S2 and lies posteriorly to the lobar bronchus. In the majority of patients, there is only one artery, while there are none or two in some patients.
Veins
In most cases, the segmental veins of the upper lobe are the two upper tributaries of the upper lobe vein:
V1 is the uppermost branch and is found in the hilum of the upper lobe. It is the most anterior and superior vessel.
V2+3 is the central vein and runs in the parenchyma and within the fissure. It gives a large posterior branch for V2 and small tributaries for V3. Actually, when V2 is large, it also provides branches to S1. It is recommended to divide only its most posterior branch.
9.2 Variations and Pitfalls
The ascending A2 can be missing. When the fissure is fused, having this information from preoperative planning is helpful to avoid useless search in the fissure.
When there are two ascending A2, the most anterior one must not be mistaken for an anterior ascending branch (A3) which supplies the anterior segment.
In about 10% of patients, the ascending A2 artery originates from the superior supply of the lower lobe or forms a common trunk with A6 (◘ Fig. 9.2a).
In many patients, a branch of A1 supplies S2 and is named recurrent A2 (Rec.A2). It usually runs along the bronchus. It can be a danger during dissection of B1 or B2 (◘ Fig. 9.2b).
A small vein (V2t) draining S2 frequently crosses the posterior aspect of the ascending A2 and must be severed before dissecting this artery (◘ Fig. 9.2c).
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