Subsuperior segmental bronchus of right lung

The subsuperior segmental bronchus (B*; Segmental bronchus of Micheau) of the right lung is the bronchus that supplies the subsuperior segment (S*), an atypical pulmonary segment located in the lower lobe of the lung, situated between the superior segment (S6) and the basal segments (S7-S10).

The subsuperior segment is not one of the standard 10 bronchopulmonary segments described in classical anatomy. It is an additional, variant segment found in the lower lobe, present in approximately 32% of individuals (18.8% on the right side, 15.8% on the left) based on a large multicenter CTbased study.[1]

The subsuperior bronchus (B*) typically arises from the basal segmental bronchus stem, between the superior segmental bronchus (B6) and the basal segmental bronchi. It runs in a posterior or posterolateral direction. In the right lower lobe, only one B* bronchus is detected per unilateral subsuperior segment, with an average diameter of approximately 2.53 ± 0.61 mm.

The subsuperior segment (S*) is typically supplied by a single pulmonary artery (in ~89% of cases), though approximately 11% have two arterial branches.

With the increasing use of anatomic segmentectomy for earlystage lung cancer and other pulmonary lesions, recognition of the subsuperior segment has become important for thoracic surgeons. Thoracoscopic anatomic S* segmentectomy has been described as a feasible procedure. The B* may also form a common trunk with B7 (medial basal bronchus) or B8 (anterior basal bronchus), which is relevant for surgical planning.[Accurate identification of this variant anatomy on preoperative CT with 3D reconstruction is essential to avoid complications during segmentectomy or bronchoscopic procedures.