Value of parametric indexes to identify tracheal atresia with or without fistula on fetal magnetic resonance imaging

Background Tracheal atresia causes some secondary changes (dilated trachea, flattened/inverted diaphragm, hyperintense and hyperinflated lungs). They can be reduced if a high airway fistula is present. Objective This study evaluated fetal MR images of tracheal atresia and the secondary changes, focusing on the presence of a fistula. Materials and methods We assessed fetal MR images of tracheal atresia without fistula ( n =4, median 26 weeks), tracheal atresia with fistula ( n =4, median 33 weeks) and controls ( n =30, median 32 weeks). We evaluated airway obstruction using true-positive rate in tracheal atresia and false-positive rate in controls indicating they are likely normal variants. Tracheal diameter, craniocaudal-anteroposterior ratio of the right hemidiaphragm, lung-to-liver signal intensity ratio, and cardiothoracic ratio were compared among the three groups using the Kruskal-Wallis test followed by pairwise comparison using the Mann-Whitney U test. Results True-positive rate was 100% in tracheal atresia, while false-positive rate was 20% in controls. The Kruskal-Wallis test showed differences among groups in craniocaudal-anteroposterior ratio and cardiothoracic ratio ( P <0.001) but not in tracheal diameter ( P =0.256) or lung-to-liver signal intensity ratio ( P =0.082). The pairwise comparison in craniocaudal-anteroposterior ratio and cardiothoracic ratio showed differences between controls and tracheal atresia without fistula ( P <0.01) and with fistula ( P <0.05). Conclusion Fetal MRI is useful for the diagnosis of tracheal atresia, and detection of airway obstruction is essential. Lower craniocaudal-anteroposterior ratio and cardiothoracic ratio might be reliable measures even if a fistula is present.