Tracheal Bronchus (Pig Bronchus)

Abstract

The tracheal bronchus is defined as a bronchial anomaly originating from the trachea or either main bronchus and directed to the upper lobe territory. These are classified [1, 2] either as displaced bronchus (when one branch of upper lobe bronchus is missing) or supernumerary bronchus (when normal branching of upper lobe is present) (Fig. 1). Any bronchus originating from the trachea between 2 cm to 6 cm from the carina and supplying the entire right upper lobe is called “true tracheal bronchus” or “bronchus sui” (or “pig bronchus” because that is the normal morphology in pigs). The incidence of true tracheal bronchus is 0.2%. Majority of these cases are asymptomatic but may present with recurrent local infections, persistent cough, stridor, acute respiratory distress, and hemoptysis. The tracheal bronchus may be associated with other anomalies which include azygos lobe, partial anomalous pulmonary venous return and displaced segmental arteries. Chest radiograph is the initial radiological investigation and it may show bronchus directly arising from the trachea, as was seen in our case. CT is imaging modality of choice as it depicts the exact tracheal and bronchial anatomy. Computed tomography virtual bronchoscopy (CTVB) is a technique in which simulated endobronchial views are generated from volumetric CT data and are helpful in the detection of endobronchial lesions, evaluation of focal stenosis, and their longitudinal extent [1]. It is important to identify the tracheal bronchus in patients undergoing cardiac surgery with one lung ventilation since serious hypoxia and atelectasis may occur if not diagnosed preoperatively [3]. In case of recurrent pneumonia complicated by bronchiectasis surgical resection of the anomalous lobe or segment is the treatment of choice [4].