Ultrasound features of an omphalocele versus gastroschisis
Omphalocele and gastroschisis are the most common abdominal wall defects, occurring in up to 1 in 4000 (omphalocele) and 1 in 10,000 (gastroschisis) live births. An omphalocele is a midline anterior abdominal wall defect containing variable herniated abdominal contents including the liver and/or bowel.
The umbilical cord inserts on the anterior aspect of the herniation, and the herniation is covered by a thin peritoneal membrane. In contrast, gastroschisis is an isolated, paraumbilical anterior abdominal wall defect of herniated free-floating bowel without an overlying peritoneal membrane.
A gastroschisis defect is most commonly to the right of the umbilical cord insertion site on the abdominal wall. Therefore, demonstrating the abdominal cord insertion site on routine second trimester US is critical to detect and differentiate abdominal wall defects. Omphaloceles carry a worse prognosis because up to 90% are associated with additional fetal malformations (including those of the cardiac, thoracic, gastrointestinal, genitourinary, and central nervous systems) and up to 40% are associated with fetal aneuploidy (trisomy 13 and 18). In contrast, gastroschisis is typically an isolated finding not seen in association with other structural abnormalities, but can be complicated by bowel malrotation, atresia, stenosis, and perforation with resulting meconium peritonitis.