Prenatal Observation of Fetal Trachea and Bilateral Bronchi using Ultrasonography

Abstract

The fetal airway tract can be observed using the planes of view in cardiac screening. In three-vessel-tracheal view, the crosssection of the trachea is identified adjacent to the right-posterior side of the middle transverse aorta. In three-vessel view, the cross-section of the right bronchus is observed adjacent to the right side of the ascending aorta. In aortic and ductal arch views, the short axis of the left bronchus is confirmed inward of the arch. In oblique three-vessel view, the right bronchus is seen on top of the ascending aorta coursing toward the azygos vein. To exclude the vessels, absence of blood flow signals in the trachea and bronchi should be reconfirmed by using pulsed and color Doppler imagings. In the whole 'Y-shaped' image, the right main bronchus depicts the more linear extension from the trachea than the left bronchus and the first lobar bronchus that branches near the carina to the right upper lobe. Segmental bronchi also can be depicted in both bilateral bronchi. Several new modalities, including three-dimensional (3D) ultrasound, simultaneous visualization of the fetal trachea and esophagus, and fluid flow waveforms in the fetal airway tract, makes feasible detailed prenatal assessment, prediction of neonatal respiratory condition, and most especially identification of anatomical deformity and pathologic entities.