The normal abdominal wall is formed by infolding of the cranial, caudal, and two lateral embryonic folds. These folds form in the 4th week of development as a combination of the parietal layer of lateral plate mesoderm and overlying ectoderm. As they move ventrally to meet in the midline, rates of cell proliferation and fusion in the folds differ. This fusion process between the folds is complex, involving cell-to-cell adhesion, cell migration, and cell reorganization. Simultaneously, as the abdominal wall is forming, the rapid growth of the intestinal tract leads to its herniation through the umbilical ring into the yolk sac from the 6th to the 10th week of gestation. By the 10th to 12th week of gestation, the intestine returns to the abdominal cavity in a well-coordinated pattern. This results in normal intestinal rotation and fixation, followed by complete formation of the abdominal wall.¹

Abnormal formation of the abdominal wall can result in omphalocele and possibly gastroschisis, which are discussed in succession.

Patient Story

A term newborn infant is found to have protrusion of the abdominal wall, involving the viscera (Figure 73-1). A prenatal diagnosis of gastroschisis had been made by ultrasound and the mother was referred to a high-risk obstetrical service for management. The infant was born via vaginal delivery and upon delivery was taken to the neonatal intensive care unit for immediate resuscitation and management. The family had met with the pediatric surgeon and neonatal intensive care team prior to the delivery. The infant underwent successful surgical repair for the defect. After a 5-week hospital course, the infant was discharged home with good bowel function.

Introduction

Gastroschisis is a full-thickness defect in the abdominal wall, typically to the right of umbilical cord (Figure 73-1), where a variable amount of intestine and/or other organs may be herniated through the abdominal wall without a membrane or covering.^2,3

Epidemiology

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  The incidence of gastroschisis seems to be increasing worldwide and is approaching 3 to 4 per 10,000 births in endemic areas.⁴

  
  
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  Recent epidemiologic studies have found a strong association between the occurrence of gastroschisis and young maternal age. However, a clear cause of gastroschisis has yet to be determined.^4,5

Etiology and Pathophysiology

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  The cause of a gastroschisis is unknown.

  
  
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  Several theories have been proposed to explain the unique abdominal wall defect through which abdominal organs may eviscerate early in gestation.⁶ These theories include:

  
  
  
  
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    Localized failure of mesoderm formation.

    
    
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    Rupture of the amnion at the umbilical ring.

    
    
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    Abnormal involution of the right umbilical vein.

    
    
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    Disruption of the right vitelline artery with subsequent localized body wall ischemia.

    
    
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    Abnormal body wall folding.

  
  
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  Gastroschisis does not appear to be strongly associated with other congenital abnormalities. It is unclear if this represents evidence that gastroschisis is not a primary developmental defect.

Risk Factors

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  Young maternal age.

Diagnosis

Prenatal Diagnosis

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  Abdominal wall defects are often diagnosed before birth by ultrasound. The specificity is greater than 95 percent, with sensitivity being more variable due to operator variability.⁷

  
  
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  A study performed on pregnant women whose fetuses had known ventral wall defects found that there was an increase in serum alpha-fetoprotein levels.⁸

Clinical Features

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  About 10 percent of babies with gastroschisis will have intestinal stenosis or atresia likely stemming from vascular insufficiency to the bowel; this insufficiency could occur early at the time of gastroschisis development or later from volvulus or compression of the mesenteric vascular pedicle against a narrowing abdominal wall ring.

  
  
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  Other associated anomalies, such as chromosomal abnormalities, are uncommon.^9,10

Differential Diagnosis

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  Omphalocele—see the following section.

Management

Prenatal Management

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  The most common associated risks for a fetus with gastroschisis include intrauterine growth retardation (IUGR), oligohydramnios, premature delivery, and fetal death.

  
  
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  Because of these associated risks, the family should undergo high-risk obstetrics care connected to a specialized pediatric center to optimize the post-partum outcome.

  
  
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  If prenatally diagnosed, the family should be introduced to the pediatric surgeon.

  
  
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  While there are no current intrauterine interventions, this introduction allows the family to be counseled about the condition, its treatment and prognosis.

Post-partum Management

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  Initial airway, breathing, and circulation evaluation and intervention if necessary.

  
  
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  Once this initial assessment and care has occurred, the next step involves placing the exposed viscera and entire lower half of the dried baby in a transparent plastic bag, commonly called a bowel bag. This allows the preservation of body heat and keeps the bowel moist. Care must be taken to support the bowel with moist gauze so that it does not fall to either side of the body and cause venous congestion and subsequent edema. This can hinder the ability to attain primary closure.

  
  
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  A small hole can be made if necessary for a lower extremity to allow for intravenous access.

  
  
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  Ensure appropriate gastric decompression.

  
  
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  Given the risk of volume loss, aggressive hydration should be part of the initial management.

Surgery

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  If a primary closure is not possible, or if there are signs of bowel ischemia, a “silo” may be placed in the operating room (Figure 73-2). A “silo” is a tubular or inverted funnel-like structure with synthetic material to give temporary cover to the abdominal viscera and allow for serial reduction of the organs into the abdominal cavity. The “silo” protects the intestine and other viscera outside the abdomen while they are slowly reduced into the abdominal cavity with daily gentle pressure.

  
  
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  This serial reduction of bowel has the goal of completely reducing the exposed viscera by the seventh to tenth day of life.

  
  
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  Another approach that is being used more recently is the “pre-fashioned” or “pre-manufactured silo.” A pre-fashioned silo is a tubularized synthetic material that comes formed from the manufacturer and does not require any suturing and can be placed at the bedside.

  
  
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  This is followed by operative closure of the abdominal wall primarily or with a synthetic patch to avoid excessive intra-abdominal pressure.