Quantification of liver herniation in fetuses with isolated congenital diaphragmatic hernia using two-dimensional ultrasonography

Objectives To describe a method of quantifying the amount of liver herniation in fetuses with isolated congenital diaphragmatic hernia (CDH) using two-dimensional ultrasonography and to correlate this finding with neonatal outcome. Methods Ultrasound images obtained from 77 consecutive fetuses that presented with isolated CDH between January 2004 and July 2012 were reviewed. Liver herniation and thoracic area were measured in a cross-sectional plane of the fetal chest at the level of the four-chamber view of the heart (the same section as is used to measure the lung area-to-head circumference ratio) and the ultrasound-derived liver-to-thoracic area ratio (US-LiTR) was calculated by dividing the liver herniation area by the thoracic area. Receiver-operating characteristics (ROC) curve analysis was used to evaluate the performance of US-LiTR in predicting neonatal outcome (survival to 6 months after delivery and need for extracorporeal membrane oxygenation (ECMO)). In addition, the US-LiTR was compared with the magnetic resonance imaging (MRI)-derived volume ratio (MRI-LiTR) and percentage of liver herniation (MRI-%LH). Results The overall neonatal mortality in the 77 cases with isolated CDH was 20.8% (16/77). ECMO was needed in 35.5% (27/76) of the newborns, with a survival rate of 52%. The US-LiTR was associated statistically with mortality (P < 0.01) and with the need for ECMO (P < 0.01). Good correlations were observed between US-LiTR and MRI-LiTR (r = 0.87; P < 0.001) and between US-LiTR and MRI-%LH (r = 0.90; P < 0.001). Based on ROC curve analysis, all three parameters had similar accuracy in predicting mortality (US-LiTR: area under the ROC curve (AUC), 0.78 (95% CI, 0.65-0.92), P < 0.01; MRI-LiTR: AUC, 0.77 (95% CI, 0.63-0.90), P < 0.01; MRI-%LH: AUC, 0.79 (95% CI, 0.65-0.92), P < 0.01, respectively) as well as the need for ECMO (US-LiTR: AUC, 0.72 (95% CI, 0.60-0.84), P < 0.01; MRI-LiTR: AUC, 0.73 (95% CI, 0.60-0.88), P < 0.01; MRI-%LH: AUC, 0.77 (95% CI, 0.64-0.89), P < 0.01, respectively). Conclusions Two-dimensional ultrasound measurement of the amount of liver herniation in fetuses with isolated CDH is feasible and demonstrates a predictive accuracy for neonatal outcome similar to that of MRI.