Branching patterns and variations of the bronchus and blood vessels in the superior segment of the right lower lobe: a three-dimensional computed tomographic bronchography and angiography study

Background: Superior segmentectomy is classified as simple due to the single intersegmental plane between the superior and basal segments. However, oncological outcomes in patients undergoing superior segmentectomy tend to be worse compared to those receiving other segmentectomy. The aim of this study is to determine the branching patterns and variations of the bronchus and blood vessels of the superior segment of the right lower lobe (RS6). Methods: Three-dimensional computed tomographic bronchography and angiography (3D-CTBA) was reconstructed in 316 patients who underwent enhanced chest computed tomography (CT) and subsequent surgery in our center from November 2018 to March 2021. Results: The bronchus in RS6 consisted of a single stem in 96.5% cases (305/316), and 2 separate stems in the remaining 3.5% cases (11/316). The artery in RS6 consisted of a single stem in 59.5% cases (188/316), 2 separate stems in 37.0% cases (117/316), and 3 separate stems in the remaining 3.5% cases (11/316). The vein in RS6 consisted of a single stem in 94.3% cases (298/316) and 2 separate stems in the remaining 5.7% cases (18/316). B6 variation was noted in 1.6% cases (5/316). A6 variation was noted in 18.0% cases (57/316), including the following: (I) coexistence of A6 and A2 (n=25); (II) A6b originating from A9+10/A10 alone (n=20); (III) A6c originating from A9+10 (n=10); and (IV) co-draining of A6 and A7 (n=2). V6 variation was noted in 11.7% cases (37/316), including the following: (I) co-draining of V6 and V2 (n=20); (II) co-draining of V6 and V4 (n=5); (III) V6 and V8+9 co-draining (n=3); (IV) V6 draining into the superior pulmonary vein (n=4); and (V) direct V6 draining into the left atrium (n=5). Conclusions: Variation of A6 and V6 in RS6 is much more common than previously reported. 3D-CTBA reconstruction is useful for pre-surgery planning.