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GASTROSCHISIS

Gastroschisis is a congenital abdominal wall defect through which intraperitoneal contents protrude (Fig. 391-1). Gastroschisis occurs in infants born to younger mothers, with a total incidence of 1 in 3000 live births. Several studies have reported a recent increase in the incidence of gastroschisis. The defect occurs to the right of the umbilical cord and can range in size. The bowel typically appears edematous and inflamed and may be covered by a fibrinous peel. The most commonly eviscerated organs include the small and large intestines and occasionally the gonads and rarely the bladder.

PATHOGENESIS AND EPIDEMIOLOGY

Gastroschisis occurs during the sixth or seventh week of gestation. The etiology of gastroschisis is unclear. The most prominent theory involves vascular compromise of the developing abdominal wall due to involution of the right umbilical vein. This theory of vascular ischemia resulting in an anatomic defect is also observed in intestinal atresia, which is associated with gastroschisis. Two other hypotheses exist for the formation of gastroschisis. One involves the defective development of the mesenchyme on the anterior abdominal wall, while the other is the failure of fusion between the lateral folds of the developing abdominal wall.

Maternal and environmental factors have been implicated in the development of gastroschisis. In animal models, folic acid deficiency, maternal hypoxia, and salicylates have been linked to abdominal wall defects. The use of vasoconstrictive agents such as pseudoephedrine, cocaine, and cigarettes in early pregnancy has been postulated to increase the risk of gastroschisis. Maternal use of salicylates and acetaminophen has also been implicated in the development of gastroschisis. Elevated atrazine levels, a chemical found in pesticides that may be present in drinking water, has recently been correlated with a regional increased incidence of gastroschisis in the United States.

Up to 25% of infants with gastroschisis have an associated intestinal anomaly. The most frequent is intestinal atresia thought to be from ischemic insult to the developing bowel. Occasionally, infants will present with vanishing gastroschisis, in which the abdominal wall defect has closed around an extruded piece of bowel. In this situation, the bowel present external to the abdominal wall may be the majority of the small bowel and can be ischemic to frankly necrotic. Infants with vanishing gastroschisis or long segment intestinal atresia are likely to have short bowel syndrome.

PRENATAL DIAGNOSIS

The diagnosis of gastroschisis is usually made using prenatal ultrasound. Ultrasonography can detect abdominal wall defects around 14 weeks of gestation. In normal development, the fetal midgut would have returned to the abdominal cavity by this time. Follow-up ultrasound should be performed if an abdominal wall defect is noted in order to detect other potential associated anomalies. Perinatologists usually pay attention to the degree of intestinal edema and ...

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