An omphalocele is caused by an opening (defect) in the middle of the abdominal wall at the bellybutton (umbilicus). The skin, muscle, and fibrous tissue are absent. The intestines protrude through the opening and are covered by fine membranes. The umbilical cord is in the center of the defect. Gastroschisis is an abnormal opening of the abdominal wall, usually to the right of the umbilicus, which allows the uncovered intestines to spill out (herniate). Both conditions are diagnosed with prenatal ultrasound.
An omphalocele is commonly associated with other birth defects (such as heart defects) and with specific genetic syndromes. Surgical closure is the treatment of choice. However, the skin of the abdominal wall must often be stretched before surgery so there is enough tissue to cover the opening. Large defects sometimes also require skin flaps.
In gastroschisis, the bowel may be damaged by compression and by exposure to amniotic fluid. Surgical closure is the treatment of choice. Large herniations may require the creation of a "silo," in which the exposed bowel is wrapped in a protective covering and suspended above the baby for several days or weeks. The silo is gradually compressed, forcing the intestines back into the abdomen.
Resource: Merck Manual Home Edition