Atypical bronchus in the right lower lobe: Computed tomography-based analysis

Introduction: The aim of this study was to define the subsuperior bronchus (B*) and reestablish the bronchial anatomy of the right lower lobe (RLL) by assessment of atypical bronchi.

Materials and methods: Chest computed tomography (CT) scans of 500 consecutive patients were retrospectively evaluated. All CT scans were acquired with 64-slice scanners. Atypical bronchi in the RLL were classified on the basis of running direction and shape: lateral (Lat), posterolateral (PL), posterior (Post), Lat + PL, and PL + Post. We classified an atypical bronchus in the basal segmental bronchus (BSB) stem running posteriorly or posterolaterally as B* and a para-lateral bronchus running laterally as Para-B8. The B* posts running posteriorly were named P1, and those running medially P2.

Results: Atypical BSB bronchi Lat, PL, and Post arose from B8, B9, and B10, respectively. All Lat + PL bronchi arose from B8 or B9, and all PL + Post from B9 or B10. When an atypical bronchus arose from one of the BSB pair, none arose from the other. Atypical bronchi forming B* and Para-B8 arose from the stem spreading the connatural BSBs. The P2 post coexisted with another atypical stem bronchus originating from B8, 9, 10, or higher.

Conclusions: The first subsegmental bronchi of B8, B9, and B10 are Lat, PL, and Post, respectively. Lat + PL and PL + Post bronchi at the BSB level could result from fusion of an atypical bronchus during downward migration. The stem B* and Para-B8 could result from arrested downward migration of atypical bronchi. This information is useful for RLL segmentectomy.