Gastroschisis

Gastroschisis is a congenital abdominal wall defect characterized by the complete lack of closure of the abdominal musculature. A portion of intestine does not return to the abdominal cavity, thereby remaining in its early embryonic herniated state but with no coverings. Diagnosis is made by prenatal ultrasonography. Findings include a paraumbilical wall defect with uncovered herniated intestines. Fetal surveillance and bowel monitoring are done to measure fetal growth and amniotic fluid volume, as well as observe any bowel changes. The mode and timing of delivery depend on these factors. Neonatal care includes protection of the exposed bowel, fluid resuscitation, and airway maintenance. Primary closure can be performed within hours of birth. The presence of a large gastroschisis or thickened and dilated bowel warrants delayed closure, with the use a bowel covering or “silo,” and serial bowel reduction.

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Overview

Definition

Gastroschisis is a full-thickness defect of the anterior abdominal wall through which the intestine and/or other abdominal viscera freely protrude.

  • No membrane or sac covers the bowel/intestine.
  • The defect is often to the right of the umbilical insertion site.

Embryology

  • Gastrointestinal (GI) system development from 3 germinal layers:
    • Mesoderm: connective tissue (wall of gut tube, blood vessels and smooth muscle)
    • Endoderm: epithelial lining
    • Ectoderm: epidermis and neural crest (neurons of the GI tract)
  • GI tract divisions:
    • Foregut: oral cavity to the 1st part of the duodenum
    • Midgut: mid-duodenum to the 1st ⅔ of transverse colon
    • Hindgut: last ⅓ of the transverse colon to the upper anus
  • 6th week of gestation:
    • Rapid growth of the GI tract
    • Midgut herniates through the umbilical ring, developing entirely outside the peritoneal cavity.
  • 10th week of gestation:
    • Abdominal cavity is large enough for the developing midgut.
    • Midgut completes rotation and returns to the abdominal cavity.
Normal process of herniation during embryologic development

Diagram showing the normal process of intestinal rotation and herniation during embryologic development

A: the midgut (multi-colored loop) before herniation.
B1-B3: as it grows rapidly, the midgut herniates through the umbilical ring, and starts rotation.
C: The midgut returns to the abdominal cavity.

Image by Lecturio.

Epidemiology

  • Prevalence: 3–4 per 10,000 births
  • Similar incidence in male and female newborns
  • In 10% of cases, gastroschisis is associated with anomalies outside the GI tract. 
  • Higher risk of preterm delivery in pregnancies with gastroschisis (28%) compared with those without gastroschisis (6%)
  • Maternal risk factors:
    • Young age (< 20 years)
    • Low body mass index (BMI)
    • Exposure to cigarette smoke
    • Intake of aspirin and ibuprofen
    • Intake of decongestants (pseudoephedrine, phenylpropanolamine)

Pathophysiology

Embryologic hypotheses leading to herniation of the bowel: 

  • Defective formation
    • Failure of mesoderm to form in the body wall
    • Abnormal folding of body wall resulting in a ventral body wall defect
  • Disruption of the abdominal wall
    • Rupture of the amnion (sac protecting the embryo) around the umbilical ring 
    • Abnormal involution of the right umbilical vein leading to weakening of the body wall
    • Disruption of the right vitelline (yolk sac) artery leading to infarction at the base of the cord and subsequent body wall damage

Diagnosis and Monitoring

Diagnostic tests

  • Ultrasonography
    • Prenatal diagnosis made as early as 14 weeks, but usually around 20 weeks’ gestation
    • Finding(s): 
      • Paraumbilical abdominal wall defect (on the right, never through the umbilicus)
      • Herniated intestines without a covering sac
      • Intestines freely floating in amniotic fluid
      • Oligohydramnios (most common amniotic fluid finding)
      • Occasionally other visceral organs also herniated (e.g., liver)
  • Laboratory test: elevated maternal serum ɑ-fetoprotein (AFP)
    • Elevated AFP is suggestive of but non-specific for gastroschisis (seen also in spina bifida and anencephaly).
    • Lab testing alone is insufficient for a diagnosis of gastroschisis.

Monitoring

  • Fetal monitoring
    • Assess fetal growth including amniotic fluid volume
    • Typically started at 24 weeks
    • Look for intrauterine growth restriction (IUGR): associated with increased risk of fetal demise
  • Fetal bowel
    • Serial sonographic evaluation of the stomach and bowel
    • Check for substantial dilation (> 25 mm) or acute thickening and edema
    • Prenatal complications associated with bowel dilation:
      • Umbilical cord compression
      • Bowel obstruction
  • Antepartum fetal surveillance
    • Biophysical profile with nonstress test and amniotic fluid index
    • Usually started around 32 weeks
  • Fetal genetic studies
    • Considered in cases with extraintestinal structural anomalies (to determine associated chromosomal abnormalities)
    • Information regarding prognosis, delivery management, and neonatal care needed

Clinical Presentation

Newborn findings

  • Full-thickness paraumbilical abdominal wall defect, usually to the right of the umbilical cord insertion site
  • Eviscerated bowel not covered by a sac 
  • Bowel appearance affected by:
    • Exposure to amniotic fluid
    • Amount of time of bowel is exposed 
    • Longer exposure to amniotic fluid → bowel is matted, thick, and covered with inflammatory rind
  • Abdominal defect is usually < 4 cm.

Categories

  • Simple gastroschisis: 
    • 75% of cases
    • Intact, uncompromised, continuous bowel
  • Complex gastroschisis: 
    • Associated with intestinal stenosis, atresia, perforation, necrosis or volvulus
    • Related to vascular compromise caused by the herniated bowel
    • More GI, infectious, and respiratory diseases
    • Higher risk for in-hospital mortality and complications (bowel obstruction, short bowel syndrome, and need for tube feedings on discharge)

Management and Prognosis

Delivery

  • Requires coordination of care among maternal-fetal medicine specialist, neonatologist, and pediatric surgeon
  • Delivery is recommended in a center with optimal neonatal care resources. 
  • Timing:
    • Affected by multiple factors, including:
      • Gestational age (lung maturity)
      • Ultrasound findings (fetal growth and bowel status)
      • Fetal testing results
    • Spontaneous labor (for pregnancies with gastroschisis) occurs at a mean gestational age of 36 weeks.
  • Mode of delivery:
    • Uncomplicated gastroschisis: not a contraindication to vaginal delivery
    • Marked liver herniation: Cesarean section should be considered.

Neonatal care

  • Reduce intestinal injury and reduce fluid loss:
    • Protect exposed bowel by wrapping bowel with sterile saline dressings covered with plastic wrap.
    • In some centers, lower half of the neonate is placed into a plastic bag (allows protection and visualization of bowel perfusion).
  • Fluid and electrolyte resuscitation (expected fluid losses are 23 times that of a healthy neonate)
  • Prophylactic broad-spectrum antibiotics (cover for maternal vaginal flora)
  • Orogastric tube insertion to decompress the stomach
  • Airway maintenance and respiratory support as needed

Surgery

  • Primary closure
    • Surgery performed within hours of birth
    • To minimize intestinal injury during reduction, abdominal defect is increased by 1–2 cm. 
    • Successful in 70% of cases
  • Delayed closure
    • In cases of thickened and distended bowel loops
    • Eviscerated bowel is contained within a sterile covering (silastic silo).
    • The bag and bowel are suspended over the infant, allowing decompression of bowel loops by gravity.
    • Serial reduction of bowel contents performed
Gastroschisis silo illustration

Gastroschisis silo

Image by Lecturio.

Prognosis

  • Gastroschisis: most favorable outcome compared with other abdominal wall defects
  • Survival rate of neonates born in North America: 98%
  • Sepsis: only significant predictor of mortality

Differential Diagnosis

  • Omphalocele: similar to gastroschisis, but due to a failure of the bowel to return to the ventral cavity after normal herniation. The abdominal viscera (including the liver) remain herniated through the umbilicus, covered by amnion and peritoneum. Unlike gastroschisis, approximately half of cases of omphalocele are associated with other birth defects and chromosomal abnormalities.
  • Pentalogy of Cantrell: a rare syndrome consisting of multiple congenital abnormalities, including a lower sternal defect, anterior diaphragm defect, pericardial defect, abdominal wall defect, and congenital heart anomalies. Diagnosis is made prenatally by ultrasonography. Treatment requires complex medical and surgical care.
  • Bladder exstrophy-epispadias complex: a spectrum of congenital defects: epispadias (failed closure of urethra), bladder exstrophy, and cloacal exstrophy (most severe defect, which includes anal atresia and an omphalocele). Treatment is surgical, with goals to close abdominal wall defect, achieve urinary continence, and reconstruct the genito-urinary area.
  • Umbilical hernia: presents as a protrusion in the neonate’s umbilical area. There is incomplete closure of the fascia of the umbilical ring but with intact skin covering the ring. It is important to determine the reducibility, as incarcerated hernia is a complication. Surgery is indicated for defects > 1.5 cm in those > 2 years of age and for complications, including strangulation, incarceration, or rupture.

References

  1. Bhatia, A., Shatanof, R., Bordoni, B. (2020) Embryology, Gastrointestinal. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK537172/ 
  2. Bradnock, T. et al. (2011). Gastroschisis: one year outcomes from national cohort study. British Medical Journal. doi: 10.1136/bmj.d6749
  3. Feldkamp, M., Carey, J., Sadler, T. (2007). Development of Gastroschisis: Review of hypothesis, and implications for research. American Journal of Medical Genetics. https://doi.org/10.1002/ajmg.a.31578
  4. Ebert, A. et al. (2009). The Exstrophy-epispadias complex. Orphanet Journal of rare diseases. 4:23. doi: 10.1186/1750-1172-4-23
  5. Glasser, J., Windle, M., Carter, B. (2019). Pediatric Omphalocele and Gastroschisis (Abdominal wall defects). Medscape. Retrieved 4 Oct 2020, from https://emedicine.medscape.com/article/975583-overview#a5
  6. Rentea, R., Gupta, V. (2020). Gastroschisis. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK557894/
  7. Stephenson, C. et al. (2020). Gastroschisis. UpToDate. Retrieved 4 Oct 2020, from https://www.uptodate.com/contents/gastroschisis?search=gastroschisis
  8. Troullioud Lucas, A., Jaafar, S., Mendez, M. (2020). Pediatric Umbilical Hernia. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK459294/-

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