Omphalocele and gastroschisis

Definition

Characteristics of the defects

• An omphalocele is a midline defect in which the hernial sac is covered by amnion and peritoneum and the umbilical cord inserts on the sac.
• Gastroschisis is typically a paraumbilical defect without a hernial sac, where intestinal loops float freely in the amniotic fluid.
• The small variant of an omphalocele is known as an umbilical cord hernia.

• Omphalocele is protrusion of abdominal viscera through a midline defect at the base of the umbilicus; the organs are covered by a thin membrane and range from a few bowel loops to stomach and liver.
• Gastroschisis is a full-thickness paraumbilical abdominal wall defect, usually to the right of the cord insertion, with protrusion of bowel without a covering membrane.

Occurrence & epidemiology

Epidemiology

• Gastroschisis occurs in about 1 in 2,500 live births and is more common than omphalocele, whose incidence is about 2 to 3 per 10,000 live births.

Aetiopathogenesis

Aetiology and associated anomalies

• In omphalocele about two thirds have further anomalies, such as bowel atresia, chromosomal abnormalities (trisomy 18, 13 and 21), cardiac and renal anomalies or Beckwith-Wiedemann syndrome.
• Gastroschisis, by contrast, is rarely associated with genetic syndromes; only about 10% have anomalies outside the gastrointestinal tract, while gastrointestinal anomalies such as malrotation and intestinal atresia occur in up to a quarter.

Clinical features

Associations and further diagnostics

• In contrast to omphalocele, chromosomal anomalies in gastroschisis are rare.

Clinical features and complications

• In gastroschisis, direct exposure to amniotic fluid causes a chemical peritonitis with an oedematous, matted bowel wall and fibrinous rind, which may later lead to fibrosis, dysmotility or obstruction; it is considered complex in the presence of atresia, stenosis, perforation, necrosis, malrotation or volvulus.
• Infants with gastroschisis frequently have growth restriction.

Diagnosis

Differentiation in the first trimester

• A physiological midgut herniation is a normal finding until about the 11th to 12th week.
• A true abdominal wall defect does not resolve during the course of the pregnancy.

Typical imaging findings

• Ultrasound: A midline sac bulges from the anterior abdominal wall, covered by a fine echogenic membrane. The umbilical cord inserts at the apex of the sac; the contents remain smoothly bordered and do not float freely.
• Ultrasound: A rounded, sharply outlined bulge with a smooth surface lies in front of the abdominal wall. The cord inserts centrally on this bulge and the contents are covered by a thin membrane.
• Ultrasound: To the right of the cord insertion bowel loops pass through the abdominal wall and lie free in the amniotic fluid without a covering membrane. Individual loops are distinguishable and float; the cord insertion itself is normal.

• Omphalocele is detected on routine prenatal ultrasound; gastroschisis typically on the ultrasound at about 20 weeks, showing bowel loops floating freely in the amniotic fluid.
• In gastroschisis, maternal serum alpha-fetoprotein is raised.

Keep learning in the app

Further reading (selection)

1. StatPearls: Gastroschisis (NCBI Bookshelf)
2. MSD Manual Professional Edition: Gastroschisis
3. MSD Manual Professional Edition: Omphalocele
4. DocCheck Flexikon, Omphalozele

Cross-references