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Synonyms: paraomphalocele, laparoschisis, abdominoschisis.

Definition: Gastroschisis is a paraumbilical defect involving all the layers of the abdominal wall, with evisceration of abdominal organs, usually the small bowel, on occasion large bowel and stomach.

Etymology: from the Greek gasthr = stomach and scixw = to split.

Prevalence: Prevalence ranges from 0.94 - 4.72^{,[3]<![endif]>,,[5]}. Smoking and inadequate prenatal care (indigent patient) seems to be risk factors for fetal gastroschisis[6]^,[7]. Males are more affected than females (M3:F2)[8].

Etiology: multifactorial, although there are some family recurrences (probably due to autosomal recessive inheritance)8^,[9].

Pathogenesis: The leading theory in the pathogenesis of gastroschisis is that the defect results from an abnormal involution (persistance) or premature atrophy of the right umbilical vein^[10]:

·         If atrophy occurs prior to the establishment of a collateral circulation from the aorta, ischemia of the surrounding tissue will cause the development of the defect.

·         At the same time persistance of the right umbilical vein compromises the development of the collateral circulation and will lead to infarction.

Hoyme et al. suggests that gastroschisis result from a disruption of the distal right omphalomesenteric artery^[11].

Tibboel et al. demonstrated that gastroschisis is a very early occurrence. In contrast the fibrous coating of the protruding bowels is a late event: chemical irritation by the amniotic fluid may cause peritonitis resulting in a progressive fibrosis and changes of the serosa^[12],[13]. However, a more recent report minimizes the role of prolonged amniotic fluid exposure in the development of bowel wall changes[14].

Sonographic findings: a small abdominal wall defect, paraumbilical, usually right-sided although there are reports of left-sided gastroshisis in association with persistent right umbilical vein[15]or with situs inversus. Gastroschisis is found either during routine second trimester screening or because of elevated maternal serum a-fetoprotein^{[16],[17],[18]}. Diagnostic accuracy ranges between 60%[19] -86.9% (up to 91% in case of ventral wall defect)[21]. However the diagnosis of gastroschisis is been made as early as 12 weeks and 3 days of gestational age[22].

Bowel dilatation and thickening are signs of ongoing intestinal damage[23] and possible bowel perforation[24].

Typical images: There are also several video-clips of Case 2 (2 MB), Case 4 (1.5 MB) Case 5 (1.8 MB) and Case 6 (4.7 MB)

Case 1: Loops of bowel protruding through a defect in the abdominal wall, not covered by a membrane.

 

Case 2: The position of the fetus may render the identification of the lesion difficult.

Case 3: Doppler demonstrated clearly that the the defect is at the right side of the umbilical insertion, as also shown by the position of the stomach. No membrane can be visualized.

More images can be seen at: Gastroschisis

Differential Diagnosis:

Omphalocele: main differential diagnosis: a defect in the anterior abdominal wall with extrusion of abdominal organs. An omphalocele is covered by a membrane (consisting of an outer layer of amnion and an inner layer of peritoneum) with the cord inserting through these covering. In contrast with gastroschisis there is a high association with other malformations and chromosomal abnormalities4 5 21.

Congenital hernia of the abdominal wall [25]^,[26]: an extra-abdominal mass on the right of the normal umbilical cord insertion.

Bladder extrophy: abdominal wall defect of the infra-umbilical region in which bladder mucosa is exposed. Ultrasound findings are absence of a fluid-filled intrapelvic bladder and a soft tissue mass seen at the lower abdomen.

Cloacal dystrophy: also known as OEIS complex: association of omphalocele, bladder extrophy, imperforate anus and spina bifida.

Limb body wall complex (body stalk anomaly): a set of disruptive abnormalities characterized by a severe body-wall defect (thorax, abdomen or both), evisceration of the abdominal organs into an amnioperitoneal sac and a shortened or absent umbilical cord[27]

Pentalogy of Cantrell: large abdominal wall defect characterized by omphalocele, ectopia cordis and disruption of the distal sternum, anterior diaphragm and diaphragmatic pericardium. It appears on ultrasound as a large thoracoabdominal wall defect containing the heart and much of the abdominal contents[28].

Beckwith Wiedeman syndrome: omphalocele, organomegaly (liver, splenic and renal enlargement), macroglossia and polyhydramnios.

Amniotic band syndrome: localized cranial, body wall or limb defects due to an amnion disruption complex.

Associated anomalies:

7%4 -30%[30] of fetuses with gastroschisis can have an associated malformation.

• Associated anomalies related to the bowel herniation are motility dysfunction, intestinal atresia

[31] and volvulus31.

Other associated anomalies are

1. undescended testes30

^,31,ventricular septum defect and a displaced gallbladder20. Anencephaly, cleft lip/palate, atrial septal defect, ectopia cordis, diaphragmatic hernia, scoliosis, syndactyly, and amniotic bands are described29.

Two reports demonstrated the development of urinary tract abnormalities during pregnancy in fetuses with isolated gastroschisis. Herniation of the bladder through the abdominal wall defect, upper tract dilatation and hydronephrosis are described[32][33].

Chromosomal anomalies are rare.

Prognosis: In general cases the survival rate is more than 95%. This is largely the result of the absence of associated anomalies and the improvement of neonatal care[34]^,[35].

The outcome is less favorable in case of intestinal thickening, distention of bowel loops, or other herniated organs. There has been much interest in the possibility of an antenatal diagnosis of early intestinal damage. Several reports described bowel dilatation (either > 10mm or >17mm) as a marker of prenatal bowel damage^{,[37],[38],[39]}. As such they conclude that prenatal sonography may be useful in selecting fetuses for preterm delivery. However, the objection to the use of these measurements as an indicator for delivery are, that at the time sonography can detect intestinal damage: the damage is already irreversible, the fetus can be too premature to deliver and not all fetuses with bowel dilatation have postnatal evidence of intestinal damage[40].

Some reports demonstrated the use of amnioinfusion as a prevention of intestinal thickening. The hypothesis is that the infusion causes a reduction of the inflammatory response in the amniotic fluid[41]^,[42]. As such the outcome improved.

Recently Sapin et al described the benefit of serial amnioinfusion in 2 cases of gastroschisis with severe oligohydramnion to decrease fetal distress[43].

Intra-uterine growth restriction is common among fetuses with gastroschisis[44]^,[45]. But Raynor and Richards demonstrated an overestimation of intra-uterine growth restriction by sonographic estimated fetal weight. They recommend the use of a formula based on percentage difference between abdominal circumference and gestational age standard of 15% or greater[46].

The mechanisms of restricted growth are not yet understood. Possible explanations include a vascular accident, the presumed cause of gastroschisis and/or the loss of nutrients and proteins across the exposed bowel wall into the amniotic fluid. Poor placental perfusion and associated anomalies may also contribute to the growth restriction.

Recurrence risk: none: sporadic8

Management: Karyotyping is usually not suggested because the incidence of chromosomal abnormalities is not greater than in the general population29.

Serial sonograms can be performed to screen for intra-uterine growth restriction, signs of bowel involvement and the involvement of other structures that might influence management and prognosis33.

The mode of delivery in case of prenatal diagnosed gastroschisis has been controversial for several years. Some authors strongly recommended primary cesarean section[47]^,[48] while others were skeptic about the benefits of cesarean section36^,[49],[50].

Although it appears rational to deliver those fetuses by cesarean section to prevent bowel injury, trauma to the exteriorized bowel can also occur during cesarean section[51]. Recently several reports[52]^,[53],[54] demonstrated that there was not any difference in outcome between vaginal delivery and elective caesarean section. As such cesarean section should be performed for obstetrical reasons only.

Reviewers: Laura Hurtado, MD; Aleksandra Novakov Mikic, MD.

References: