Congenital Tracheal Bronchus: The Inability to Isolate the Right Lung with a Univent Bronchial Blocker Tube

Abstract

Implications 

Tracheal bronchus is a congenital anomaly in which the right upper lobe bronchus originates from the lateral tracheal wall. This anatomic variant is reported in approximately 1 of 250 patients at bronchoscopy. Although it is usually of little clinical significance, this atypical origin of the right upper lobe bronchus may complicate one-lung ventilation during thoracic surgery.

Tracheal bronchus is a congenital anomaly in which the right upper lobe bronchus originates from the lateral wall of the trachea (¹). In some large mammalian species, including swine, the right upper lobe bronchus normally arises from the trachea, leading many to refer to this anatomic variant as a “bronchus suis” or “pig bronchus.” Although frequently regarded as an incidental finding in approximately 1 of 250 patients at bronchoscopy (²), tracheal bronchus may be associated with stridor, recurrent pneumonia, and bronchiectasis (³). During conventional endotracheal intubation, the distal tracheal tube can obstruct the anomalous bronchus. This may lead to right upper lobe atelectasis and hypoxemia (⁴). We report a case in which the presence of an undiagnosed tracheal bronchus made isolation of the right lung with a bronchial blocker impossible.

Case Report

A 19-yr-old, 72-kg, 175-cm man, with an ostium secundum type atrial septal defect, was scheduled to undergo closure of the defect by using a right thoracotomy approach. His only complaint was intermittent chest pain associated with exertion. Physical examination of the patient revealed fixed splitting of the second heart sound with normal breath sounds in all lung fields. The preoperative chest radiograph was unremarkable.

After anesthetic induction, a 7.5-mm Univent Bronchial Blocker Tube (Fuji Systems Corp, Tokyo, Japan) was easily placed in the trachea by using direct laryngoscopy. A fiberoptic bronchoscope was inserted through this tube to visualize what was thought to be the right main bronchus. The bronchial blocker was advanced into this lumen and the balloon inflated with 3 mL of air. Auscultation of the chest demonstrated that breath sounds over the right chest, although diminished, were still present. A repeat bronchoscopic examination showed the presence of a smaller lumen approximately 3 cm proximal to the tracheal carina (Fig. 1). This proximal tracheal bronchus resulted in continued ventilation of the right upper lobe of the lung, despite positioning of the bronchial blocker in the right main bronchus.

Figure 1: Fiberoptic examination of the distal trachea shows the anomalous right upper lobe bronchus (arrow) approximately 3 cm proximal to the carina.

The Univent tube was withdrawn and replaced with a left-sided, 37F double-lumen endotracheal tube. Subsequent bronchoscopy clearly showed the correct position of the bronchial lumen in the left mainstem bronchus and the presence of the anomalous tracheal bronchus. Right lung isolation was satisfactory and allowed the completion of the procedure as planned. At the conclusion of the procedure, the trachea was extubated, and the patient made an uneventful recovery.

Discussion

Difficulty with double-lumen tube placement in a patient with a tracheal bronchus has been previously described (⁵), but this is the first report of failure to achieve right lung isolation with a Univent bronchial blocker tube in a patient with this anomaly. The use of the Univent tube is a recognized option to provide one-lung ventilation during anesthesia (^5–8). The main advantages are the ease of placement for pediatric patients (⁹) and patients with a difficult airway (^10–12) or tracheostomy (¹³) and the avoidance of a tube exchange at the end of the procedure.

In this case, the tracheal bronchus was overlooked during initial bronchoscopy. The bronchial blocker, although correctly positioned in the right main bronchus, would have failed to provide satisfactory isolation of the lungs necessary for optimal surgical exposure. The clinical finding of diminished, but still present, breath sounds over the right chest can be explained by the patent tracheal bronchus that allowed ventilation of the right upper lobe. Had a careful bronchoscopic examination been initially performed, the tracheal bronchus would have been diagnosed, and the decision to replace the Univent tube with a left-sided double-lumen endotracheal tube would have been made sooner. The confirmation of normal right bronchial anatomy can be made by correctly identifying the origin of the right upper lobe bronchus approximately 1 to 3 cm distal to the tracheal carina. Failure to identify this structure by using bronchoscopy should raise suspicion of an anomalous bronchus. The clinician using a Univent tube must be aware of this anomaly and perform a careful bronchoscopic examination before advancing and inflating the bronchial blocker.