Gastrochisis

Gastrochisis, literally gastro (stomach) schisis (splitting), is a full thickness abdominal wall defect to the right of the umbilical cord insertion site into the fetal abdomen, with evisceration of bowel usually to the right of the umbilical cord.¹ No synonyms.

Incidence has been increasing over last 25 years from 0.1-1.0:10,000 to now 3.0-5.0 per 10,000.²

Most cases occur in younger women. In women under 20, there is a four-fold increase in risk compared to 30 or older. Exposures associated with gastrochisis include smoking, drug use (methamphetamines, cocaine), and possibly pseudoephedrine.³ Interestingly, researchers from the CDC found that the incidence of gastochisis is higher in countries with high and medium opiate prescribing rates as compared to low rates, independent of changes in demographic trends relating to age, race, or ethnicity.⁴ It is unclear why the incidence of gastroschisis has risen world-wide.²

There are multiple theories regarding the pathogenesis of gastrochisis. The most common theory proposed is that gastroschisis results from an early teratogenic insult which disrupts the differentiation of the somatopleural mesenchyme. Without this supportive mesenchymal layer, the ectoblastic layer is reabsorbed, resulting in a defect similar to the normal process seen in the formation of the oral or cloacal membranes.⁵  Another theory involves the rupture of the umbilical cord hernia before complete closure of the umbilical ring, which is a similar pathogenesis to the formation of omphalocele.⁶ Another popular theory suggests that a vascular insult causes intrauterine interruption of the omphalomesenteric artery. This last theory is supported by the association between smoking, amphetamine, or cocaine use with incidence of gastroschisis.⁷

Gastrochisis is associated with other GI anomalies including intestinal atresia, a “Christmas tree deformity,” volvulus and infarction of the bowel. These anomalies may be caused by the underlying pathogenesis of the gastrochisis or as a result of injury or constriction of the bowel due to exposure to amniotic fluid. Gastroschisis is considered “complex” when large amounts of bowel and/or stomach are seen outside of the abdominal cavity and additional bowel abnormalities are identified.⁸ Prenatal ultrasound may not identify all bowel abnormalities.

Gastroschisis is typically not associated with an increased probability of an underlying chromosomal abnormality; risk of aneuploidy is equal to the risk conferred by maternal age or a priori risk based on screening tests done in the first or second trimester. Extra-gastrointestinal anomalies which have been observed include pulmonary defects (1%), non-descended testicles (6.8%), and cardiac defects (4%).⁸

Recurrence risk is approximately 3-5% and is thought to be multifactorial, involving both genetic and environmental factors.⁹

Maternal serum alpha fetoprotein (MS AFP) of >2 MoM has a 99% sensitivity for gastrochisis. Cases of gastroschisis typically have higher levels of MS AFP than do cases of omphalocele.¹⁰

The diagnosis of gastroschisis is made by ultrasound. Typical findings include a full thickness defect in anterior abdominal wall, invariably to the right of the umbilical cord. In gastrochisis, color Doppler will demonstrate a normal umbilical artery insertion into the abdomen. Diameter of the defect is usually 2-3 cm. The length of the defect is difficult to measure with ultrasound. A variable number of free loops of bowel are seen floating in the amniotic fluid. An extra-abdominal stomach may be seen in severe cases. Occasionally, the stomach may be seen to slide into the defect or slide in and out of the defect as the pregnancy progresses.¹¹

It is important to differentiate gastroschisis from omphalocele as omphalocele is more commonly associated with extra-gastrointestinal anomalies and chromosomal abnormalities. Omphalocele presents as herniated bowel with peritoneo-amniotic membrane covering. If extracorporeal liver is visualized, consider an alternative diagnosis, including a ruptured omphalocele. Color Doppler will help to identify the cord insertion site into the abdomen in cases of gastroschisis or into the membrane in cases of omphalocele.  

1. Omphalocele
2. Midline disruption sequence
3. Cloacal exstrophy sequence: omphalocele, bladder exstrophy, imperforate anus, spinal anomalies
4. Cystic or edematous umbilical cord
5. Vesicoallantoic cyst/patent urachus

Diagnosis in the very early first trimester is difficult due to normal herniation of midgut into the umbilical cord; therefore, detection before 12 weeks is challenging. Studies comparing methods of estimating fetal weight recommend Hadlock’s formula as the most accurate.¹² Estimating fetal weight may be difficult as abdominal circumference measurements may underestimate fetal weight since a portion of the bowel is extracorporeal. Doppler evaluation of the fetal circulation is suggested to further screen for IUGR. Fetuses with elevated indices should be managed as per IUGR protocols. Surveillance should be considered beginning at 32 weeks or earlier if there is IUGR with evaluation of the fetal bowel for obstruction, biophysical profile (BPP) and Doppler.¹²

The condition of the bowel is the most important prognostic factor affecting long-term outcome.¹ Atresia and necrosis typically require resection and hypoperistalsis and poor absorptive capacity may result in delayed return of normal bowel function. There has been inconsistent success in screening using ultrasound markers such as small bowel dilation or mural thickening.¹¹ A dilated fetal stomach is associated with volvulus and neonatal death.¹

Overall, survival is greater than 90%.¹³

IUGR is present in 77% of fetuses. This may be an overestimation due to smaller abdominal circumference measurement.¹² A proposed mechanism is peritoneal protein losses due to the abdominal wall defect.¹⁴ Iatrogenic prematurity resulting in delivery between 34-36 weeks is associated with delay in reaching full enteral feeds, prolonged hospitalization and higher incidence of sepsis as compared to delivery at 37 weeks or greater.¹⁵ This requires balancing the risk of stillbirth with neonatal complications. There is an increased risk of preterm labor in fetuses with gastroschisis which may be a result of polyhydramnios. The incidence of stillbirth is as high as 12.5%.¹

There is no recommended intrauterine intervention. There is no demonstrated benefit to cesarean delivery except for routine obstetric indication.¹

Management consists of surgical intervention after delivery and supportive enteral feeds until bowel function returns. Simple gastrochisis cases can be managed with primary closure of the defect. More complex cases involving atresias are managed with staged surgeries with siloing.¹ Some fetuses may require reoperation for bowel atresias which were not evident at the primary surgery.

1. Kirby RS, Marshall J, Tanner JP, et al. ; National Birth Defects Prevention Network. Prevalence and correlates of gastroschisis in 15 states, 1995 to 2005. Obstet Gynecol 122(2013):275–8.

2. Jones AM, Isenburg J, Salemi JL, et al. Increasing Prevalence of Gastroschisis — 14 States, 1995–2012. MMWR Morb Mortal Wkly Rep 65(2016):23–26.

3. Werler MM, Mitchell AA, Shapiro S. Demographic, reproductive, medical, and environmental factors in relation of gastroschisis. Teratology. 45(1992):353-60.

4. Short TD, Stallings EB, Isenburg J, et al. Gastrochisis trends and ecologic link to opioid prescription rates- United States, 2006-2015. MMWR Morb Mortal Wkly Rep 68(2019):31-36.

5. Duhamel B. Embryology of Exomphalos and Allied Malformations. Arch Dis Child. 38(1963):142–147.

6. Shaw A. The myth of gastrochisis. J Ped. 10(1975):235.

7. Hoyme HE, Higginbottom MC, Jones KL. The vascular pathogenesis of gastroschisis. J Ped. 98(1981): 228–231.

8. Abdullah F, Arnold MA, Nabaweesi R, et al. Gastrochisis in the United States 1988-2003: analysis and risk categorization of 4344 patients. Perinat. 27(2007):50-55.

9. Salinas-Torres, V.M., Salinas-Torres, R.A., Cerda-Flores, R.M. et al. Pediatr Surg Int 34(2018): 277. 

10. Palomaki GE, Hill LE, Knight GJ, Haddow JE, Carpenter M. Second-trimester maternal serum alpha-fetoprotein levels in pregnancies associated with gastroschisis and omphalocele. Obstet Gynecol. 71(1988):906-909.

11. Brun M, Grignon A, Guibaud L, et al. Gastroschisis: Are prenatal ultrasonographic findings useful for assessing the prognosis? Ped. Rad.10(1996):723-6.

12. Zaki MN, Lusk LA, Overcash RT et al. Predicting birth weight in fetuses with gastrochisis. Journal of Perinatology 38(2018): 122-126.

13. Fullerton BS, Velazco CS, Sparks EA, et al. Contemporary Outcomes of Infants with Gastroschisis in North America: A Multicenter Cohort Study. Peds. 188(2017): 192-197.

14. Landisch RM, Yin Z, Christensen M, et al. Outcomes of gastroschisis early delivery: a systematic review and meta-analysis. J Pediatr Surg. 52(2017): 1962-1971.  

15.Carnaghan H, Baud D, Lapidus-Krol E, et al. Effect of gestational age at birth on neonatal outcomes in gastrochisis. J Ped Surg. 51(2016):734-8.