Multimodality Evaluation of Fetal Congenital Diaphragmatic Hernia and Its Mimics SA–CME REVIEW (Method 2) is depicted in Figure 9. 7 The circumferential tracing meth- od is a more reproducible method than methods. The lung area is then divided by head circumference to calculate the LHR. The LHR can then be compared to reference values. Another calculator can be found at perinatology.com (https://www. perinatology.com/calculators/LHR. htm). 9 Based on different studies, there is 100% fetal mortality with LHR< 0.6-1 and 100% survival with LHR> 1.35-1.4. 4 Other prognostic features that can be assessed on ultrasound include the location of the fetal liver. If the fetal liver is above the diaphragm, this can Figure 6. CHAOS on US and MRI in a fetus of 17 weeks’ gestational age. (A) This coronal obstetric ultrasound image shows a dilated trachea (arrow) and enlarged, echogenic lungs. (B) Coronal T2 SSFSE image obtained one week later re-demonstrates fluid filled trachea (arrow) below the level of tracheal stenosis and enlarged lungs with increased signal on T2 imaging. Both images show massive ascites and eversion of the diaphragm. A B Figure 7. Left-sided CDH on US. Axial obstetric ultrasound of the fetal chest at 27 weeks’ gestational age demonstrates left CDH with fetal stomach (curved arrow) in the chest and resultant mass effect causing rightward deviation of the heart (arrow). (RT =right, LT = left) Figure 8. Lung area for CDH on obstetric US. Obstetric US image shows the lung area outlined by tracer method, which is then used to calculate the lung area-to-head circumference ratio. (Arrow = stomach) Applied Radiology 11 November / December 2022