True Tracheal Bronchus

Aberrations in tracheobronchial branching patterns are occasionally encountered during tracheobronchosopy. In this case, a 19-year-old man with chronic respiratory insufficiency and subsequent tracheotomy at an outside hospital was sent for evaluation of his tracheotomy, with exam findings as shown in Figure 1 . Approval was obtained from The Johns Hopkins Hospital Institutional Review Board for submission of this report.

Figure 1.

Tracheal view during flexible bronchoscopy demonstrating right tracheal bronchus (asterisk). Carina with right and left mainstem distally.

Discussion

Tracheal bronchus is a rare anomaly referring to a bronchus stemming directly from the trachea. ¹ While there are several anatomic variations and classification schemes, it is key to distinguish aberrant bronchi from diverticula, which lack lung parenchyma. ² Once a tracheal bronchus is known to communicate with lung parenchyma, its classification hinges on configuration of right mainstem and right upper lobe (RUL) bronchi. “Supernumerary” tracheal bronchus implies normal right mainstem branching. ¹ A “displaced” tracheal bronchus occurs in the setting of absent RUL branches from the mainstem bronchi. If the tracheal bronchus is the only branch serving the RUL, it is termed a “pig bronchus” or “true tracheal bronchus.” In this case, the right “mainstem” is the bronchus intermedius serving the right middle and lower lobes, which is the normal morphology in pigs. ¹ In our patient, distal arborization of the tracheal bronchus ( Figure 2 ) coupled with the presence of only 2 branches off the right mainstem bronchus suggests a true tracheal bronchus.

Figure 2.

View from within the right tracheal bronchus, demonstrating arborization.

While these variations are often asymptomatic and discovered incidentally, they can have clinical significance. Reduced pulmonary clearance from aberrant anatomy may increase risk of recurrent RUL pneumonia. ³ Squamous cell carcinoma of a tracheal bronchus has been reported. ⁴ In addition, the presence of a tracheal bronchus can complicate endotracheal tube intubation, either through occlusion or direct intubation of the aberrant bronchus. ⁵ It is important for those performing tracheoscopy and bronchoscopy to be familiar with variations in tracheobronchial anatomy that may be encountered.

Author Contributions

Patrick O. McGarey Jr., analysis and interpretation of data, drafting, critical revision; Lee M. Akst, conception of the work, data acquisition, drafting, critical revision.

Disclosures

Competing interests: None.

Sponsorships: None.

Funding source: None.