An abdominal wall defect is an opening in the abdomen through which various abdominal organs can protrude. This opening varies in size and can usually be diagnosed early in fetal development, typically between the tenth and fourteenth weeks of pregnancy.

There are two main types of abdominal wall defects: omphalocele and gastroschisis. Omphalocele is an opening in the center of the abdominal wall where the umbilical cord meets the abdomen. Organs (typically the intestines, stomach, and liver) protrude through the opening into the umbilical cord and are covered by the same protective membrane that covers the umbilical cord.

Gastroschisis is a defect in the abdominal wall, usually to the right of the umbilical cord, through which the large and small intestines protrude (although other organs may sometimes bulge out). There is no membrane covering the exposed organs in gastroschisis.

Fetuses with omphalocele may grow slowly before birth (intrauterine growth retardation) and they may be born prematurely. Individuals with omphalocele frequently have multiple birth defects, such as a congenital heart defect. Additionally, underdevelopment of the lungs is often associated with omphalocele because the abdominal organs normally provide a framework for chest wall growth.

When those organs are misplaced, the chest wall does not form properly, providing a smaller than normal space for the lungs to develop. As a result, many infants with omphalocele have respiratory insufficiency and may need to be supported with a machine to help them breathe (mechanical ventilation). Rarely, affected individuals who have breathing problems in infancy experience recurrent lung infections or asthma later in life.

Affected infants often have gastrointestinal problems including a backflow of stomach acids into the esophagus (gastroesophageal reflux) and feeding difficulty; these problems can persist even after treatment of omphalocele. Large omphaloceles or those associated with multiple additional health problems are more often associated with fetal death than cases in which omphalocele occurs alone (isolated).

Omphalocele is a feature of many genetic syndromes. Nearly half of individuals with omphalocele have a condition caused by an extra copy of one of the chromosomes in each of their cells (trisomy). Up to one-third of people born with omphalocele have a genetic condition called Beckwith-Wiedemann syndrome. Affected individuals may have additional signs and symptoms associated with these genetic conditions.

Individuals who have gastroschisis rarely have other birth defects and seldom have chromosome abnormalities or a genetic condition. Most affected individuals experience intrauterine growth retardation and are small at birth; many affected infants are born prematurely.

With gastroschisis, the protruding organs are not covered by a protective membrane and are susceptible to damage due to direct contact with amniotic fluid in the womb. Components of the amniotic fluid may trigger immune responses and inflammatory reactions against the intestines that can damage the tissue. Constriction around exposed organs at the abdominal wall opening late in fetal development may also contribute to organ injury.

Intestinal damage causes impairment of the muscle contractions that move food through the digestive tract (peristalsis) in most children with gastroschisis. In these individuals, peristalsis usually improves in a few months and intestinal muscle contractions normalize. Rarely, children with gastroschisis have a narrowing or absence of a portion of intestine (intestinal atresia) or twisting of the intestine.

After birth, these intestinal malformations can lead to problems with digestive function, further loss of intestinal tissue, and a condition called short bowel syndrome that occurs when areas of the small intestine are missing, causing dehydration and poor absorption of nutrients. Depending on the severity of the condition, intravenous feedings (parenteral nutrition) may be required.

The health of an individual with gastroschisis depends largely on how damaged his or her intestine was before birth. When the abdominal wall defect is repaired and normal intestinal function is recovered, the vast majority of affected individuals have no health problems related to the repaired defect later in life.

Frequency

Abdominal wall defects are uncommon. Omphalocele affects an estimated 2 to 2.5 in 10,000 newborns. Approximately 2 to 6 in 10,000 newborns are affected by gastroschisis, although researchers have observed that this malformation is becoming more common. Abdominal wall defects are more common among pregnancies that do not survive to term (miscarriages and stillbirths).

Genetic Changes

No genetic mutations are known to cause an abdominal wall defect. Multiple genetic and environmental factors likely influence the development of this disorder. Omphalocele and gastroschisis are caused by different errors in fetal development.

Omphalocele occurs during an error in digestive tract development. During the formation of the abdominal cavity in the sixth to tenth weeks of fetal development, the intestines normally protrude into the umbilical cord but recede back into the abdomen as development continues. Omphalocele occurs when the intestines do not recede back into the abdomen, but remain in the umbilical cord. Other abdominal organs can also protrude through this opening, resulting in the varied organ involvement that occurs in omphalocele.

The error that leads to gastroschisis formation is unknown. It is thought to be either a disruption in the blood flow to the digestive tract or a lack of development or injury to gastrointestinal tissue early in fetal development. For reasons that are unknown, women under the age of 20 are at the greatest risk of having a baby with gastroschisis. Other risk factors in pregnancy may include taking medications that constrict the blood vessels (called vasoconstrictive drugs) or smoking, although these risk factors have not been confirmed.

Inheritance Pattern

Most cases of abdominal wall defect are sporadic, which means they occur in people with no history of the disorder in their family. Multiple genetic and environmental factors likely play a part in determining the risk of developing this disorder.

When an abdominal wall defect, most often omphalocele, is a feature of a genetic condition, it is inherited in the pattern of that condition.

Other Names for This Condition

• abdominal hernia
• gastroschisis
• hernia, abdominal
• omphalocele

Demographics

Abdominal wall defects, specifically gastroschisis and omphalocele, are rare and occur in only once in every 5000 births. Both boys and girls have these defects in equal numbers. While infants with gastroschisis rarely have defects other than those affecting the intestines, of children with omphalocele, 50 percent to 75 percent have associated congenital anomalies and 20 percent to 35 percent have chromosomal abnormalities.

Gastroschisis

• Congenital anterior abdominal wall defect that occurs as a small, full-thickness periumbilical cleft leading to herniation of the abdominal contents into the amniotic sac.
• Usually only includes the small intestine, but can also include stomach, colon, and ovaries.
• The defect typically occurs to the right of the umbilical cord insertion.
• No covering sac and no associated syndromes

Pathogenesis

Vascular Theory: premature involution of right umbilical artery leading to ischemia consequently leads to a weak spot that subsequently ruptures causing herniation.

Risk Factors

Genetic: increased risk in siblings of patients with gastroschisis

Environmental:

Vasoactive drugs: pseudoephedrine, aspirin, ibuprofen, acetaminophen

Young maternal age, alcohol, smoking, white race

Complications

Gastroschisis may be associated with inflamed, volvulized, strangulated, or perforated intestine

Approximately 10% will have concurrent intestinal atresia or stenosis. 20-60% have IUGR likely secondary to placental anomalies and direct nutritional wasting.

Omphalocele

 Midline abdominal wall defect characterized by eviscerated abdominal contents covered by a protective sac. Occurs most commonly at the base of the umbilical stalk.

Includes small bowel, Wharton’s jelly, amnion, +/- colon and liver

• Epidemiology:1/5000
• 30-60% have karyotype abnormalities
• Trisomies 13, 18, and 21 are most common
• 50% with cardiac defects
• Frequently associated with syndromic presentations:
• Beckwith-Wiedemann (gigantism, macroglossia, omphalocele, and hypoglycemia)
• CHARGE (coloboma, heart defects, choanal atresia, mental retardation, and genitourinary and ear anomalies)

VACTERL (vertebral, anal, cardiac, tracheoesophageal, renal, and limb deformities)

Treatment

Immediate Postpartum: Protection of exposed viscera and thermoregulation (predisposed to hypothermia, particularly with gastroschisis). Orogastric tube, initiation of IV fluids, and ventilator assistance when necessary.

Gastroschisis

Surgical resection if necrosis or perforation present with subsequent stomas

If viable: can reduce with primary closure or serial reduction with delayed closure. Primary if possible without compartment syndrome

Delayed: placement of preformed silo and once or twice daily ligation of the solo until the contents are entirely reduced

Omphalocele

Large (if > 4 cm at base):

Treated with daily silver sulfadiazine to promote progressive epithelialization.

A body wrap is placed and progressively tightened to facilitate reduction of abdominal contents.

Elective repair of fascial defect after 6 months minimum and usually after 2 years

Small (more frequently associated with karyotype abnormalities):

Closed primarily or epithelialized with delayed closure.

For primary, must be reducible without producing abdominal compartment syndrome.

Outcomes

Gastroschisis

Directly related to severity of GI disease. Mortality is 4-7% (extensive necrosis, atresia, short bowl syndrome)

Complications: ileus, catheter infections, sepsis

Omphalocele

Dependent on associated anomalies: isolated omphalocele has mortality of 10%, but increases to 60% when other anomalies are present.

Common complications: ileus, infection, sepsis

Some studies demonstrate nearly 2x risk of premature delivery for infants with abdominal wall defects

If neonatal survival achieved, excellent long-term outcomes for both isolated omphalocele and uncomplicated gastroschisis

As adults: healthy- most common complaints are scarring, intermittent abdominal pain, and GERD

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