Bilateral anteromedial defect of the diaphragm in children.

Four cases are reported, along with a review of the literature, to demonstrate the radiographic and clinial spectrum of bilateral anteromedial defect of the diaphragm in infants and children. Bilateral anteromedial defect of the diaphragm produces a characteristic radiographic pattern on herniation of abdominal structures through a single midline opening. The usually solid herniated structures elevate the heart and thymus producing a three-tiered snowman appearance. The lateral chest view substantiates the anterior location differentiating anteromedial herniation from eventration, partial or complete. Diagnosis can be confirmed by pneumoperitoneography but the high incidence of liver herniation allows less invasive determination by radionuclide scanning. While many patients will be asymptomatic, clinical symptoms can be severe due to pulmonary compression and hypoplasia or associated cardiovascular abnormalities.