Lung growth index and lung growth ratio - new ultrasound parameters for predicting neonatal survival in fetuses with isolated left sided congenital diaphragmatic hernia?

Objective: To evaluate the accuracy of several ultrasound parameters used to predict neonatal survival in fetuses with isolated left-sided severe congenital diaphragmatic hernia. This study is to compare different measurement methods. Also, two new ultrasound parameters have been described: the lung growth ratio (LGR) and the lung growth index (LGI).Methods: This was a retrospective study in pregnancies with a congenital diaphragmatic hernia (CDH) treated by fetoscopic tracheal occlusion (FETO). Pictures revealing four-chamber view of the fetal heart were reviewed and the right lung area was remeasured with several techniques: anterior-posterior, longest diameter, and tracing method. Based on the measurements, different parameters were obtained: lung-to-head ratio (LHR) (anterior-posterior), LHR (longest diameter), LHR (tracing method), o/e LHR (longest diameter), quantitative lung index (QLI) (longest diameter), and QLI (tracing method). All measurements were taken at the time of balloon insertion and at the time of balloon removal. In order to describe and compare fetal lung size indices in terms of their value as predictors of neonatal survival, receiver operating characteristic (ROC) analysis was applied.Results: Lung-to-head ratio calculated at the time of balloon occlusion measured with the tracing method reached the most significant statistical difference (p < .01) and the best combination of sensitivity, specificity, and accuracy. Neither of the two new parameters (LGR and LGI) was better compared to previously described indices. Among all analyzed parameters, LHR measured with the tracing method at the time of balloon removal was the best predictor of neonatal survival.