Diagnosis of retrotracheal left brachiocephalic vein with prenatal ultrasound: a case report

Retroesophageal or retrotracheal left brachiocephalic vein (LBCV) is a rare anatomic variant that is often associated with congenital heart disease. It is rarely reported in fetal life, and an isolated fetal retroesophageal LBCV has a good prognosis: it is typically asymptomatic, although respiratory symptoms or swallowing disorders occasionally occur. A variant was observed on fetal echocardiography at 22(+6) weeks of gestation. The 3-vessel view revealed a transverse section of a vessel to the left of the pulmonary artery. Tracing upwards along its long axis showed that the left subclavian vein joined the left internal jugular vein to form the LBCV, and tracing downwards revealed that the vessel traveled to the right and lower side, where it merged into the superior vena cava via the azygos vein behind the aortic arch. The variant was identified as retrotracheal LBCV. Three-dimensional (3D) reconstruction of fetal great vessels was performed using temporal spatial correlation imaging. The left internal jugular vein and the left subclavian vein converged into the LBCV, then bypassed behind the trachea and converged into the superior vena cava via the azygous vein. As a 3D technique, spatio-temporal image correlation (STIC) can visualize the abnormal courses of LBCV, thus improving the diagnostic accuracy. This article presents the 2-dimensional (2D) ultrasound, color Doppler, and STIC findings of an isolated retrotracheal LBCV, which may inform the sonographic diagnosis of such variants.