Ultrasound Interactive Case Study: Cardiac Outflow Tract size in Fetus with Diaphragmatic Hernia

Case Presentation by: Dr. R. Udayakumar, Chennai, India - November 2000

This fetus was scanned at 37weeks GA and has a large diaphragmatic (Bochdalek) hernia. 

The heart is pushed to the right and the left hemithorax is occupied by the stomach, and small and large bowel. Views of the cardiac outflow tracts show a relative large MPA compared to aortic root size. Could this be due to increased pulmonary pressure secondary to the herniated viscera? 

TRV Fetal Chest	TRV Fetal Chest	Views of the outflow tracts

This patient had an outside ultrasound at  20weeks and the "stomach bubble" appeared normal. Literature check suggests that diaphragmatic hernias may at times be identified only in the 3rd trimester and sometimes only in late postnatal life in case of small defects. But can a case like this be missed at 20weeks? The criteria for identifying diaphragmatic hernia would include displaced stomach bubble and mediastinal shift. Are there any others?