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Quadrivial Pattern of Division in the Right Upper Lobe: The Axillary Bronchus

Conci, Diego I. MD

Journal of Bronchology & Interventional Pulmonology: April 2014 - Volume 21 - Issue 2 - p 182–183
doi: 10.1097/LBR.0000000000000062
Letters to the Editor

Cleveland Clinic Foundation Beachwood, OH

Disclosure: There is no conflict of interest or other disclosures.

To the Editor:

Lobar bronchi, also known as secondary bronchi, arise from the primary bronchi and serve as a specific lung lobe airway. The right main bronchus subdivides into 3 lobar bronchi. The right upper lobe orifice averages 10 mm and has many variations, the most common one is trifurcating into apical, posterior, and anterior segmental bronchi. It corresponds to the Boyden classification B1, B2, and B3 segmental bronchi.1 Each of these endup subdividing to supply 2 bronchopulmonary subsegments.

Variations in the airways are believed to be the result of developmental disturbances of the lungs, such that an inappropriate number of lung buds develop or arise at atypical sites. Most bronchial anomalies are on the right, and a tracheal bronchus and supernumerary superior segmental bronchus are among the most common findings.2

Occasionally, an extra bronchus supplies the lateral aspect of the right upper lobe. This axillary bronchus is usually a subsegmental bronchus, but may arise as a segmental branch. When segmental, the axillary bronchus most often originates adjacent to the posterior bronchus. Rarely, an axillary segment can also be present on the left.

Foster-Carter have reported this fourth segmental bronchus arising from the right upper lobe bronchus and supplying an “axillary” segment in approximately 10% of cases.3 Other authors describe instead a “quadrivial type of branching” occurring in 5.3% to 16% of cases.1,4–6

In these cases, if it is a segmental bronchus, the axillary bronchus most often originates adjacent to the posterior bronchus.

Airspace disease in the axillary subsegment has a characteristic appearance on radiologic studies. Awareness of this variant anatomy may explain an otherwise confusing finding, and can help in obtaining samples. These images were obtained from surveillance bronchoscopies and depict the presence of the axillary segment (Figs. 1–3).







Diego I. Conci, MD

Cleveland Clinic Foundation, Beachwood, OH

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© 2014 by Lippincott Williams & Wilkins.