Objectives: To prospectively examine the relationship between contralateral lung area measured by two-dimensional (2D) ultrasound examination and contralateral and total fetal lung volume (FLV) estimated by magnetic resonance imaging (MRI) in the assessment of fetuses with congenital diaphragmatic hernia (CDH).
Methods: Sixty-six fetuses with isolated CDH were entered in this prospective study. Contralateral fetal lung area was measured by 2D ultrasonography using the longest axis method. Ipsilateral, contralateral and total FLV were measured using multiplanar axial T2-weighted MRI. Regression analysis was used to determine the significance of associations between contralateral lung area and contralateral and total FLV, and the predicted total FLV was subsequently calculated using the regression equation. Univariate regression analysis was used to investigate the effect on the proportionate difference between the predicted and the observed total FLV of gestational age, proportionate volume of ipsilateral vs. total FLV, side of CDH, intrathoracic herniation of the liver and intratracheal presence of a balloon.
Results: The 66 fetuses underwent a total of 191 paired 2D ultrasound and MRI examinations at a median gestational age of 30 (range, 18-38) weeks. It was possible to visualize and measure the contralateral lung area by 2D ultrasound, as well as both the ipsilateral and contralateral lung volumes by MRI, in all instances. There was a significant association between contralateral lung area and contralateral lung volume (r = 0.86; P < 0.001) and with total FLV (r = 0.84; P < 0.001). Univariate regression analysis showed that the proportionate difference between the predicted and the observed total FLV was significantly associated with the proportionate volume of ipsilateral vs. total FLV but not with gestational age, side of CDH, intrathoracic herniation of the liver or intratracheal presence of the balloon.
Conclusions: In CDH, contralateral lung area measurement by 2D ultrasound correlates well with the total FLV estimated by MRI, irrespective of gestational age, liver herniation or side of herniation. Inconsistencies between the two measurements are attributable to the contribution of the ipsilateral lung to the total lung volume.