Congenital bronchial abnormalities revisited.

Bronchial anatomy is adequately demonstrated with the appropriate spiral computed tomographic technique on cross-sectional images, multiplanar reconstruction images, and three-dimensional reconstruction images. Contrary to the numerous variations of lobar or segmental bronchial subdivisions, abnormal bronchi originating from the trachea or main bronchi are rare. Major bronchial abnormalities include accessory cardiac bronchus (ACB) and "tracheal" bronchus. An ACB is a supernumerary bronchus from the inner wall of the right main bronchus or intermediate bronchus that progresses toward the pericardium. Fourteen ACBs were found in 17,500 consecutive patients (frequency, 0.08%). The term tracheal bronchus encompasses a variety of bronchial anomalies originating from the trachea or main bronchus and directed to the upper lobe. In a series of 35 tracheal bronchi, only eight originated from the trachea, three originated from the carina, and 24 originated from the bronchi. Displaced tracheal bronchi (27 of 35) are more frequent than supernumerary tracheal bronchi (eight of 35). Minor bronchial abnormalities include variants of tracheal bronchus, displaced segmental bronchi, and bronchial agenesis. The main embryogenic hypotheses for congenital bronchial abnormalities are the reduction, migration, and selection theories. Knowledge and understanding of congenital bronchial abnormalities may have important implications for diagnosis, bronchoscopy, surgery, brachytherapy, and intubation.