Chronic pneumonitis due to displaced segmental bronchus with accessory fissure
Presentation
Cough for 2 months. Rhonchi in both lungs. Treated as bronchial asthma for many years.
Patient Data
CT Chest
Apical segmental bronchus of right upper lobe (RUL) arises directly from superolateral wall of the right principal bronchus <2 cm distal to carina, instead of from upper lobar bronchus at right hilum. Right upper lobar bronchus gives rise to intermediate bronchus for middle lobe (RML) as well as segmental branches for anterior and posterior segments of upper lobe, as normal. There is no separate middle lobe, and horizontal fissure is incomplete. Apical segment of RUL is demarcated by accessory fissure. However, azygos vein is identified in its normal position along medial surface of right upper lung. Thin linear opacities with dilated airways having thickened walls involve apical segment of RUL. Small calcified nodule in superior segment of right lower lobe (RLL).
Left lung contains small wedge-shaped area of airspace densification with air bronchogram at the anterior surface of the lingula. Tiny nodules are scattered all over left lung. Tiny bulla in superior segment of left lower lobe (LLL).
Mediastinum contains a prominent lymph node in prevascular station.
Case Discussion
The apical segmental bronchus of the right upper lobe is categorized as "displaced" since it originates from a higher order airway than normal hierarchy, i.e. from a principal bronchus instead of from a lobar bronchus 1. Some authors include such airways under the category of "tracheal bronchus" if they arise within 2 cm distal to the carina 2.
The fissure across the apex of the right lung is categorized as an accessory fissure and not azygos fissure, since the azygos vein is identified in its normal position along the medial surface of the right lung. The term "tracheal lobe" has been used previously (in contrast with "azygos lobe") to label an area supplied by a tracheal bronchus and also demarcated by an accessory fissure 3.
It is important for the treating clinician to note that the chronic inflammatory changes, fibrosis, bronchiectasis, etc. in such patients are due to the anomalous configuration of bronchi and fissures. In extreme cases, segmentectomy or lobectomy may be necessary to prevent recurrent infections.