5 month old male child with acute respiratory tract infection, CT coronal reformatted lung window shows bronchus arising from the trachea on right side (arrow) and the virtual bronchoscopy image shows the tracheal bronchus opening better.
The term tracheal bronchus refers to an abnormal bronchus that comes directly off the lateral wall of the trachea (ie, above the main carina) and supplies ventilation to the upper lobe. It is most often an asymptomatic anatomical variant found on bronchoscopy. There is an association
between tracheal bronchus and other congenital malformations, mainly malformations of the ribs and vertebrae. Patients with Down syndrome have a higher incidence of tracheal bronchus. The anomalous bronchus can arise anywhere from the carina to the cricoid cartilage, but most frequently within 2 cm of the carina. Tracheal bronchi are classified as being either “displaced” or “supernumerary.”
If the entire right upper lobe takes off from the trachea the right main bronchus is the bronchus intermedius, feeding the right middle and lower lobes, and the malformation is called “true tracheal bronchus” or “bronchus sui” (“pig bronchus,” because that is the normal morphology in pigs). The incidence of true tracheal bronchus is 0.2%.
If the anomalous bronchus is the take-off of the apical segment of the right upper lobe, as was the case in our patient, the right main bronchus will be normal looking, but the right upper lobe will not have its trifurcation. Instead there will be a bifurcation, corresponding to the anterior and posterior segments. That variant is called “apical tracheal bronchus,” which has been described in patients who have an azygos lobe. In that situation the apical segment will have its own displaced bronchus and its ownpleural investment. Vascular supply and venous drainage are usually normal in the displaced bronchus variant and are provided by the pulmonary artery and pulmonary veins.
The majority of patients with tracheal bronchi are asymptomatic and do not require any medical intervention. In the case of recurrent pneumonia complicated by bronchiectasis surgical resection of the anomalous lobe or segment is the treatment of choice.