An omphalocele is a defect of the muscles of the abdominal wall that develops in the fatal stage. The intestines, liver and occasionally other organs are then located outside of the abdomen in a translucent membrane sac. The defect can be small, with only a small loop of intestines present outside the abdomen, or large, with most of the abdominal organs protruding from the abdomen (giant omphalocele). In severe cases surgical treatment is complicated by the abnormally small volume of the infant’s abdomen – as there was no need for expansion to accommodate the developing organs. Giant omphalocele is often associated with lung hypoplasia (sometimes severe) for which respiratory support is needed.
Approximately 25–40% of infants with an omphalocele have other birth defects. These may include genetic problems (chromosomal abnormalities), congenital diaphragmatic hernia, and heart defects. A ’small’ type omphalocele (involving protrusion of a small portion of the intestine only) occurs in one of every 5,000 live births. A giant omphalocele (involving protrusion of the intestines, liver, and other organs) occurs in one of every 10,000 live births.