Fetal Surgery for Gastroschisis

1. Definition & Overview

• Defect is almost always to the right of the umbilicus (right umbilical vein involution theory)
• No overlying membrane (unlike omphalocele)
• Defect size typically < 4 cm
• Herniated organs exposed directly to amniotic fluid → inflammation, thickening, peel formation

Gastroschisis. Defect to the right of the normal umbilicus; bowel is thickened, inflamed, and covered with inflammatory peel. — Mulholland & Greenfield's Surgery, 7e

2. Epidemiology & Risk Factors

3. Pathogenesis

1. Somatopleural mesenchyme fails to differentiate → abdominal wall mesoderm fails to form
2. Amnion rupture at base of umbilical ring during physiologic gut herniation
3. Right umbilical vein premature involution → weakness at resorption site (most widely accepted)
4. Right vitelline (omphalomesenteric) artery disruption
5. Abnormal body wall folding
6. Multifactorial: identified gene variants (NOS3, NPPA, ADD1, ICAM1, ICAM4, ICAM5, MTHFR) interacting with environmental exposures

Routine antenatal US has documented gastroschisis arising from ruptured hernia of the umbilical cord in utero — supporting a mechanical rather than global embryogenetic defect.

4. Prenatal Diagnosis

Ultrasonographic Features

Sagittal view at 22 weeks' gestation showing gastroschisis with typical "cauliflower" appearance. — Creasy & Resnik's, 9e

• Multiple loops of bowel floating freely in amniotic fluid — "cauliflower" appearance
• Defect at right side of abdominal cord insertion (color Doppler confirms)
• Intraabdominal and extraabdominal dilated bowel loops may appear late in pregnancy
• Complex gastroschisis: intraabdominal bowel dilation AND/OR liver or bladder herniation
• Maternal serum AFP elevated — 95% of cases diagnosed prenatally with widespread screening

Differential Diagnosis

• Aneuploidy: isolated gastroschisis is NOT typically associated with chromosomal abnormalities → invasive testing not routinely warranted (unlike omphalocele, where 40% have aneuploidy)

5. Classification

6. Associated Anomalies

• ~85% occur in isolation
• Intestinal atresia/stenosis in ~10% (due to mechanical/vascular compromise of herniated bowel)
• Rarely: complete loss of small bowel from volvulus in utero
• Non-GI anomalies (arthrogryposis, cardiac, genitourinary) < 5%
• Oligohydramnios common; polyhydramnios with concomitant bowel atresia
• Fetal growth restriction (FGR) often present — standard Hadlock formula underestimates weight (AC is undersized); use Siemer or Shepard formulas

7. Antenatal Management

1. Serial ultrasound to monitor:
   • Fetal growth
   • Amniotic fluid volume
   • Bowel dilation (consistency of data as prognostic marker is limited)
2. Doppler assessment of umbilical and cerebral arteries
3. Fetal echocardiogram to confirm normal cardiac anatomy
4. Non-stress test / biophysical profile twice weekly from 32–34 weeks (earlier if growth restriction)
5. Multidisciplinary consultation: neonatology + pediatric surgery pre-delivery
6. Delivery planning:
   • Consider induction at 37 weeks to reduce bowel damage and shorten time to oral feeds
   • Delivery before 37 weeks only if non-reassuring fetal status or poor growth
   • No advantage to cesarean over vaginal delivery
   • Early delivery (< 36 weeks) → significantly longer hospital stay and time to enteral feeds

8. Rationale for Fetal Intervention

• Amniotic fluid is intrinsically toxic to bowel serosa → inflammation, thickening, peel
• Leads to delayed GI motility, prolonged NICU stay, TPN dependence
• Gastroschisis is one of the leading causes of short bowel syndrome and intestinal transplantation in children
• Theoretical goal: intervene in utero to minimize bowel damage before birth

"There is currently no proven effective in utero intervention… To date, maternal-fetal intervention for gastroschisis remains limited to experimental models." — Sabiston Textbook of Surgery, 21e

9. Current Status of Fetal Intervention

9a. Fetoscopic In Utero Repair (Complex Gastroschisis)

• Currently under investigation — open Phase I feasibility study evaluating fetoscopic in utero repair of complex gastroschisis
• Rationale: reduce bowel exposure duration in most severely affected cases
• Technique would mirror fetoscopic MMC repair: minimally invasive endoscopic access to amniotic cavity
• Major limitation: preterm delivery risk, PROM, chorioamnionic separation

9b. Transamniotic Stem Cell Therapy (TRASCET) — Experimental

• Amniotic fluid naturally contains fetal mesenchymal stem cells (MSCs) with wound-healing properties
• Amniotic fluid exerts dual effects: it damages bowel (toxicity) but also participates in healing via native stem cells
• TRASCET delivers a concentrated dose of expanded amniotic fetal MSCs via intra-amniotic injection → tips the balance toward healing

• Rodent model of gastroschisis: bowel damage reduced when amniotic fetal MSCs delivered in concentrated dose via intra-amniotic injection
• Fetal MSCs show trilineage potential and unique wound-healing capability
• TRASCET also applied to CDH models → reduction in arterial wall thickness vs. untreated group

1. Expanded fetal MSCs delivered by intra-amniotic injection in utero
2. Infant born → postnatal surgery to reduce abdominal viscera and close defect
3. Normal postnatal surgical pathway followed

9c. Animal Modeling — Feasibility Established

• Early animal studies confirmed in utero surgical intervention is safe in a fetal sheep model of gastroschisis
• Rodent and ovine models have been primary platforms for testing TRASCET and fetoscopic approaches

10. Postnatal Surgical Treatment (Standard of Care)

Initial Resuscitation

• Vigorous IV fluid resuscitation: 160–190 mL/kg/day to replace evaporative losses
• Cover exposed bowel to minimize heat and fluid loss
• Prophylactic antibiotics

Surgical Options

Caution during reduction: monitor bladder or airway pressures to prevent abdominal compartment syndrome from elevated intraabdominal pressure.

Postoperative Course

• Intestinal function returns over several weeks (especially if bowel is thickened/edematous)
• Central line placement + TPN required
• Feeding advancement is slow — weeks to reach full enteral nutrition
• If intestinal atresia present at primary repair → reduce bowel, return in weeks after edema resolves to correct atresia

11. Prognosis

• Pliable, non-distended → uncomplicated course likely
• Distended, atretic, or necrotic → worse prognosis

12. Key Takeaways for Fetal Surgery

• Sabiston Textbook of Surgery, 21e — Maternal-Fetal Surgery ch.
• Creasy & Resnik's Maternal-Fetal Medicine, 9e — Gastroschisis ch.
• Mulholland & Greenfield's Surgery, 7e — Gastroschisis ch.
• Schwartz's Principles of Surgery, 11e — Gastroschisis ch.