Subsuperior segmental artery of right lung

The subsuperior segmental artery of the right lung (A*) is the pulmonary artery branch that supplies the subsuperior segment (S*), an atypical (variant) pulmonary segment located in the lower lobe of the right lung, situated between the superior segment (S6) and the basal segments (S7S10).

The subsuperior segment is not one of the standard 10 bronchopulmonary segments described in classical pulmonary anatomy. Rather, it is a variant segment that arises when an additional bronchus the subsuperior bronchus (B*) branches from the lower lobe bronchus between the superior segmental bronchus (B6) and the basal segmental bronchi. The subsuperior segmental artery (A*) is the corresponding pulmonary arterial branch that accompanies B* and provides arterial blood supply to this variant segment.

Key Anatomical Characteristics

• Prevalence: A multicenter study of 2,194 CT scans with 3D reconstruction found the subsuperior segment in approximately 32% of individuals, with a slightly higher prevalence on the right side (18.8%) than the left (15.8%).

• Arterial supply: In most cases (approximately 89%), the subsuperior segment is supplied by a single pulmonary artery (A*), though about 10.7% of cases have two arteries supplying the segment.

• Bronchial anatomy: Only one subsuperior bronchus (B*) is typically present per side, with an average diameter of approximately 2.5 mm.

• Location: The subsuperior segment occupies a position dorsal and inferior to S6, interposed between the superior segment and the basal pyramid of the lower lobe. The medial basal bronchus (B7) has been observed to form a common trunk with B* in some cases.

• Intersegmental veins: One intersegmental vein is the most common configuration on both sides, though absence of a clear intersegmental vein between S* and the basal segments has been reported in a substantial proportion of cases (up to ~60% of B* cases on the left side).

Surgical Relevance

Recognition of the subsuperior segment and its artery has become increasingly important with the growing use of anatomical segmentectomy for early-stage lung cancer. Thoracoscopic subsuperior segmentectomy has been described as a feasible procedure. Preoperative 3D-CT bronchography and angiography (3D-CTBA) is recommended for identifying this variant anatomy and planning safe segmental resections, as failure to recognize A* can lead to inadvertent vascular injury or incomplete resection.