Lateral basal segmental artery of right lung

The lateral basal segmental artery of right lung (A9) is a branch of the right inferior lobar pulmonary artery that supplies the lateral basal segment (S9) of the right lower lobe of the lung.

Origin and course

The right main pulmonary artery divides at the hilum into a superior trunk (truncus anterior) and an inferior trunk (interlobar artery). The interlobar artery descends within the oblique fissure alongside the bronchus intermedius and gives off the segmental arteries to the lower lobe. After the superior segmental artery (A6) branches off, the interlobar artery continues as the basal trunk, which gives rise to the basal segmental arteries A7 (medial basal), A8 (anterior basal), A9 (lateral basal), and A10 (posterior basal). A9 closely accompanies the lateral basal segmental bronchus (B9) and courses laterally and inferiorly to supply the lateral basal bronchopulmonary segment.

Anatomical relationships

The segmental artery typically lies toward the lung periphery relative to its corresponding bronchus in this case, positioned laterally or anterolaterally to B9. The segmental veins, by contrast, run centrally (medially) relative to the bronchus and drain into the inferior pulmonary vein. The lateral basal segment (S9) occupies the lateral and inferior portion of the right lower lobe, bordered by the anterior basal segment (S8) anteriorly and the posterior basal segment (S10) posteriorly.

Anatomical variations

Considerable variability exists in the basal segmental arteries. A9 may arise as a single vessel, or it may share a common trunk with A10 (forming an A9+10 trunk) or with A8. The segmental arteries may also be duplicated or even triplicated in up to 20% of cases. Studies using 3D CT angiography have identified at least 11 distinct branching variations in the right lower lobe basal segment vasculature. Accurate preoperative identification of these variants is essential before thoracoscopic segmentectomy, as S9 segmentectomy is considered one of the most technically challenging anatomical segmentectomies due to the deep location of the target vessels within the lung parenchyma.