Abdominal Wall Defects

Introduction:

Gastrointestinal Development:

  • 3rd week: Rapid growth of ectoderm and mesoderm leads to ventral folding of the embryo around endoderm. This process involves four body walls: cranial, caudal, and two lateral, which normally approximate to form the umbilical ring.
  • 6th week: Physiologic herniation of the midgut through the umbilical ring, intestinal rotation counterclockwise 270 degrees
  • 10th week: Spontaneous reduction of herniation

Gastroschisis

  • Congenital anterior abdominal wall defect that occurs as a small, full-thickness periumbilical cleft leading to herniation of the abdominal contents into the amniotic sac.
  • Usually only includes the small intestine, but can also include stomach, colon, and ovaries.
  • The defect typically occurs  to the right of the umbilical cord insertion.
  • No covering sac and no associated syndromes

gastroschisis-web_small.jpg

http://www.cdc.gov/ncbddd/birthdefects/gastroschisis.html

Epidemiology

  • 1/10,000 but increasing  

Pathogenesis

  • Vascular Theory: premature involution of right umbilical artery leading to ischemia consequently leads to a weak spot that subsequently ruptures causing herniation.

Risk Factors

  • Genetic: increased risk in siblings of patients with gastroschisis

  • Environmental:

    • Vasoactive drugs: pseudoephedrine, aspirin, ibuprofen, acetaminophen

    • Young maternal age, alcohol, smoking, white race

Complications

  • Gastroschisis may be associated with inflamed, volvulized, strangulated, or perforated intestine

  • Approximately 10% will have concurrent intestinal atresia or stenosis. 20-60% have IUGR likely secondary to placental anomalies and direct nutritional wasting.

Differential Diagnosis

  • Prune-belly (Eagle-Barrett) syndrome- acongenital absence of abdominal wall musculature,  cryptorchidism, ureteral, bladder, and urethral anomalies.

  • Umbilical hernia: incomplete closure of the umbilical ring after separation of the umbilical stalk. Epithelialized skin overlies the defect

Omphalocele

  •  Midline abdominal wall defect characterized by eviscerated abdominal contents covered by a protective sac. Occurs most commonly at the base of the umbilical stalk.
  • Includes small bowel, Wharton’s jelly, amnion, +/- colon and liver

omphalocele-web_small.jpg

http://www.cdc.gov/ncbddd/birthdefects/omphalocele.html

Epidemiology:

  • 1/5000

  •  30-60% have karyotype abnormalities

  • Trisomies 13, 18, and 21 are most common

  • 50% with cardiac defects

  • Frequently associated with syndromic presentations:

    • Beckwith-Wiedemann (gigantism, macroglossia, omphalocele, and hypoglycemia)

    • CHARGE (coloboma, heart defects, choanal atresia, mental retardation, and  genitourinary and ear anomalies)

    • VACTERL (vertebral, anal, cardiac, tracheoesophageal, renal, and limb deformities)

Pathogenesis

  • Result of incomplete lateral body wall folding during umbilical ring formation in the 3rd – 4th week which leads to incomplete reduction of the physiologic hernia.

  • Risk Factors

    • Alcohol and tobacco use during pregnancy

    • SSRIs

    • Maternal Obesity

    • Karyotype abnormalities

  • Giant omphalocele: Defect with diameter greater than 5 cm with liver contained in the herniated sac, or cases in which more than 75% of the liver is in the sac.

    • Associated with lower likelihood of chromosomal abnormalities

Complications

  • Most morbidity and mortality is due to associated anomalies

  • Intestinal complications less common than with gastroschisis due to protective sac

Diagnosis

  • Prenatal: Ultrasound has sensitivity of 60-75% and specificity of 95% for both omphalocele and gastroschisis.
    • Gastroschisis associated with a very high AFP (7-9 fold) whereas omphalocele more mild AFP elevation (4 fold)
    • Diagnosed based on AFP and antepartum ultrasound in 98% of cases
    • Management: No definitive evidence for induced preterm delivery or elective cesarean- no survival benefits demonstrated. Case reports of omphalocele rupture with vaginal delivery

Treatment

  • Immediate Postpartum: Protection of exposed viscera and thermoregulation (predisposed to hypothermia, particularly with gastroschisis). Orogastric tube, initiation of IV fluids, and ventilator assistance when necessary.
  • Gastroschisis
    • Surgical resection if necrosis or perforation present with subsequent stomas
    • If viable: can reduce with primary closure or serial reduction with delayed closure. Primary if possible without compartment syndrome
    • Delayed: placement of preformed silo and once or twice daily ligation of the solo until the contents are entirely reduced
  • Omphalocele
    • Large (if > 4 cm at base):
      • Treated with daily silver sulfadiazine to promote progressive epithelialization.
      • A body wrap is placed and progressively tightened to facilitate reduction of abdominal contents.
      • Elective repair of fascial defect after 6 months minimum and usually after 2 years
    • Small (more frequently associated with karyotype abnormalities):
      • Closed primarily or epithelialized with delayed closure.
      • For primary, must be reducible without producing abdominal compartment syndrome.

Outcomes

  • Gastroschisis 
    • Directly related to severity of GI disease. Mortality is 4-7% (extensive necrosis, atresia, short bowl syndrome)
    • Complications: ileus, catheter infections, sepsis
  • Omphalocele
    • Dependent on associated anomalies: isolated omphalocele has mortality of 10%, but increases to 60% when other anomalies are present.
    • Common complications: ileus, infection, sepsis
  • Some studies demonstrate nearly 2x risk of premature delivery for infants with abdominal wall defects
  • If neonatal survival achieved, excellent long-term outcomes for both isolated omphalocele and uncomplicated gastroschisis
  • As adults: healthy- most common complaints are scarring, intermittent abdominal pain, and GERD

gastroschisis_omphalocele_0_0.png

Chabra et al., NeoReviews, 2005

References:

  1. Alwan S, Reefhuis J, Rasmussen SA, Olney RS, Friedman JM, National Birth Defects Prevention Study. Use of selective serotonin-reuptake inhibitors in pregnancy and the risk of birth defects. N Engl J Med. 2007;356(26):2684-2692. doi:10.1056/NEJMoa066584.
  2. Chabra S, Gleason CA. Gastroschisis Embryology, Pathogenesis, Epidemiology. NeoReviews. 2005;6(11):e493-e499. doi:10.1542/neo.6-11-e493.
  3. Davis AS, Blumenfeld Y, Rubesova E, et al. Challenges of Giant Omphalocele From Fetal Diagnosis to Follow-up. NeoReviews. 2008;9(8):e338-e347. doi:10.1542/neo.9-8-e338.
  4. Kastenberg ZJ, Dutta S. Ventral Abdominal Wall Defects. NeoReviews. 2013;14(8):e402-e411. doi:10.1542/neo.14-8-e402.
  5. Mac Bird T, Robbins JM, Druschel C, et al. Demographic and environmental risk factors for gastroschisis and omphalocele in the National Birth Defects Prevention Study. J Pediatr Surg. 2009;44(8):1546-1551. doi:10.1016/j.jpedsurg.2008.10.109.
  6. Parker SE, Mai CT, Canfield MA, et al. Updated National Birth Prevalence estimates for selected birth defects in the United States, 2004-2006. Birt Defects Res A Clin Mol Teratol. 2010;88(12):1008-1016. doi:10.1002/bdra.20735.
  7. Waller DK, Shaw GM, Rasmussen SA, et al. Prepregnancy obesity as a risk factor for structural birth defects. Arch Pediatr Adolesc Med. 2007;161(8):745-750. doi:10.1001/archpedi.161.8.745.
  8. Williams LJ, Kucik JE, Alverson CJ, Olney RS, Correa A. Epidemiology of gastroschisis in metropolitan Atlanta, 1968 through 2000. Birt Defects Res A Clin Mol Teratol. 2005;73(3):177-183. doi:10.1002/bdra.20114.

 

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