Subsuperior segmental bronchus of left lung

The subsuperior segmental bronchus (B*) of the left lung is a variant bronchial branch that arises between the superior segment (S6) and the basal segments (S8, S9, S10) of the left lower lobe, giving rise to the subsuperior segment (S*). It is not one of the standard 10 bronchopulmonary segments described in classical anatomy, but rather an atypical, anatomically variable segment found in a subset of the population.

Key anatomical features:

• Prevalence: The subsuperior segment is present in approximately 24%-32% of patients on the left side.

• Location: B* branches off between the superior segmental bronchus (B6) and the basal bronchial trunk in the lower lobe. It forms a segment (S) that occupies the territory between S6 superiorly and the basal segments inferiorly.

• Branching pattern: In most cases, only a single B* bronchus is present unilaterally, with an average diameter of approximately 2.53 mm. About half of B* branches course in a dorsolateral or dorsal direction. In a minority of cases (~4%), B* diverges directly from the trunk of the basal bronchus rather than from the lower lobe bronchus.