Feasibility of quantitative measurement of fetal trachea and bilateral bronchial angles by ultrasound to diagnose heterotaxy syndrome in middle and late pregnancy

Objective To analyze the feasibility of prenatal ultrasound quantitative measurement of the angles between trachea and bilateral bronchi as a new diagnostic tool for fetuses with heterotaxy syndrome. Methods The angles between trachea and bilateral bronchi were measured at 18-34+6 gestational weeks for 200 fetuses with normal ultrasound findings (normal group) and 41 fetuses with heterotaxy syndrome [35 right atrial isomerisms (right group) and six left atrial isomerisms (left group)] diagnosed by ultrasound and confirmed after abortion or induction (case group) in Chongqing Health Center for Women and Children from October 2015 to December 2018. Scatter plots of left/right bronchus angle (α/β) ratios were drawn. Differences in bilateral bronchus angles between the three groups were statistically analyzed using one-way analysis of variance and paired t-test. Results In the normal group, scatter plots showed the α/β ratios were relatively constant at 0.8-1.0 with larger β than α (t=-33.14, P 0.05] and presented as bilateral right bronchial angle; in the left group, the β value decreased and was close to the α value [(147.38±3.16)° vs (148.82±5.56)°, t=-1.18, P>0.05] and presented as bilateral left bronchial angle. There were significant differences in the α and β values among the normal group, the right and left groups (all P<0.05), and the bronchial angles of the right group were both greater than those of the left group (all P<0.05). Conclusions Prenatal ultrasound measurement of the angles between trachea and bilateral bronchi can be used as an indirect indicator for the diagnosis of heterotaxy syndrome. Key words: Heterotaxy syndrome; Ultrasonography, prenatal; Trachea; Bronchi