The bridging bronchus: A comprehensive review of a rare, potentially life-threatening congenital airway anomaly associated with cardiovascular defects.

The bridging bronchus is a rare congenital airway anomaly in which the right upper lobe of the lung is supplied by the right main bronchus while the right lower lobe, and often the right middle lobe is supplied by an aberrant bronchus arising from the left main bronchus. The aberrant bronchus crosses (bridges) the lower part of the mediastinum, hence the term bridging bronchus (BB). This potentially life-threatening condition, usually accompanied by diffuse or focal airway stenosis, commonly presents with signs and symptoms related to large airway obstruction, such as respiratory distress, apnea, wheezing, stridor, and recurrent respiratory tract infections. Diagnosis of the BB is often challenging because the associated signs and symptoms mimic those of common conditions such as bacterial and viral bronchiolitis, bronchial asthma, cystic fibrosis, and foreign body aspiration. The BB is also often accompanied by congenital cardiovascular anomalies, including left pulmonary artery sling, atrial, and ventricular septal defects, tetralogy of Fallot, patent ductus arteriosus, and coarctation of the aorta. Patients presenting with the above signs and symptoms who are not responsive to standard treatment modalities, and have accompanying cardiovascular congenital anomalies should, therefore, be investigated for the BB. Herein, we review the anatomy, embryology, clinical presentation, differential diagnosis, imaging techniques and surgical management of the BB.