Gastroschisis: A birth defect in which there is a separation in the abdominal wall. Through this opening protrudes part of the intestines which are not covered by peritoneum (the membrane that normally lines the inside of the abdomen). The opening in the abdominal wall in gastroschisis is never at the site of the umbilicus (the navel or belly button). Rather, the umbilicus is characteristically to the left of the gastroschisis and is separated from it by a bridge of skin.
By contrast, an omphalocele is an opening in the abdominal wall that is right at the site of the umbilicus. "Omphalo-" indicates a relationship to the umbilicus (the navel) and the suffix "-cele" refers to a hernia or rupture, so an omphalocele = a hernia or rupture at the umbilicus. While the protruding part of the intestine in gastroschisis is not covered by the peritoneum, that in an omphalocele is covered by peritoneum (as well as by the amniotic membrane).
Gastroschisis and omphalocele differ fundamentally in how they arise. An omphalocele is caused by an error in the embryonic development of the intestinal tract. During normal development of the embryo, there are initially three distinct portions of the intestinal tract (the foregut, midgut and hindgut) that extend the length of the embryo. Much of the midgut is temporarily herniated (protruded) outside the abdomen at the umbilicus (belly button). The midgut later reenters the abdomen (belly) and the opening in the abdominal wall closes. The error responsible for an omphalocele is a failure for the midgut to return and reenter the abdomen. The opening in the abdominal wall cannot close because to do so would pinch off part of the intestines.
Gastroschisis is due to a herniation (rupture) at the base of the umbilical cord that allows variable amounts of intestine to herniate out (pouch out) into the amniotic fluid. This event can take place antenatally (before birth) or perinatally (around the time of birth).
Omphalocele and gastroschisis together make up most of the major defects of the abdominal wall. Omphalocele is more common and affects about 1 in 5,000 newborn babies. Gastroschisis occurs in about 1 in 11,000 babies
The treatment of gastroschisis is to carefully wrap it in pads soaked in saline (salt solution) so the herniated intestines do not dry out, put in a nasogastric tube to remove air and decompress the intestines, do an abdominal ultrasound to identify the nature of herniated viscera, and then surgically repair the gastroschisis by returning the herniated intestines to the abdomen and then closing the abdominal wall.