eMedicine Specialties > Pediatrics: Cardiac Disease and Critical Care Medicine > Neonatology

Omphalocele and Gastroschisis

Author: James G Glasser, MD, Clinical Associate Professor, Department of Surgery and Pediatrics, Department of Pediatric Surgery, University of South Carolina Medical School; Consulting Staff, Palmetto Health Alliance Children's Hospital
Contributor Information and Disclosures

Updated: Jul 22, 2009

Introduction

Background

Gastroschisis and omphalocele are among the group of congenital anomalies most frequently encountered by pediatric surgeons. Their combined incidence is 1 in 2,000 births; hence, a pediatric surgeon sees twice as many babies with abdominal wall defects as babies with esophageal atresia and a tracheoesophageal fistula.

Although pediatric surgeons and neonatologists initially treat these babies, pediatricians should become familiar with the clinical spectrum of abdominal wall defects so that they are prepared to care for these children. If the baby's abdomen was closed during the neonatal period, routine pediatric care may suffice; however, if the abdominal wall defect was one component of a multifaceted anomaly, further care by specialists who are familiar with the child's particular problems may be required. 

A baby who is born with gastroschisis may have associated malabsorption, either from in utero injury to the intestine or partial bowel obstruction. Anomalies of intestinal fixation accompany the abdominal wall defects, and midgut volvulus is possible. Atypical appendicitis may occur, if the abnormally located appendix was not removed. In addition, these children may have gastroesophageal reflux, and Hirschsprung disease may complicate their clinical course.

Pathophysiology

Embryology¹

Embryologic development is aptly described by the term orchestrated. An orchestra is a complex entity that is composed of disparate parts whose spatial arrangement and temporal function are highly specified and rigorously governed by a master plan (ie, the musical score). Growth of the fetus and definition of its form occur by processes that are operative at specific times and locations. Growth spurts are punctuated by rests. Proliferation and differentiation of cells, and migration and deposition occur as specified in the genetic master plan. 

The embryo is initially a flat disc surrounded by the umbilical ring, defined histologically by the junction of the cylindrical epiblast epithelium and the cuboidal hypoblast epithelium. The epiblast becomes either neuroectoderm or surface epithelium, and the hypoblast becomes the inner epithelium of gut-derived organs (endoderm). A third germ layer, the mesoblast, appears coincident with growth of the embryonic disc. As it elongates, longitudinal enfolding of its lateral walls creates the appearance of a cylinder. At this stage, a recognizable body plan can be discerned.

Several processes combine to form the mesoblast cell layer:

• Apoptotic cell death with disruption of the epithelial basement membrane
• Phagocytosis of the dead cells with enlargement of the intercellular space
• Migration of ectoderm cells from the epithelial layer to the mesodermal layer

These processes take place in 3 areas:

• The primitive streak, a groove-like structure in the dorsocaudal portion of the embryo
• The neural crest, located in the cranial half of the embryo delineated by the transition of neuroectoderm and surface epithelium
• The umbilical ring

Proliferation of the neuroectoderm and underlying mesoderm pushes the embryonic disc above the umbilical ring and the contained yolk sac like a sprouting mushroom. Simultaneously, the embryo folds ventrally, separating the thoracic and abdominal cavities from the extraembryonic coelom. The amniotic cavity bulges over the embryo; and the amnion attaches to the yolk sac and the connecting stalk to form the umbilical cord. Caudal folding of the embryo incorporates the proximal yolk sac into the hindgut and the allantois (a diverticulum of the yolk sac) into the urogenital sinus. The cloacal membrane covers the openings of the hindgut and urogenital sinus; and the perineum lies between these openings. The primitive gut and the urogenital sinus elongate, whereas the adjacent mesoderm coalesces in the midline forming the urorectal septum.

In summary, the human embryo initially has 2 layers and looks like a disc. As it acquires a third cell layer, it becomes cylindrical; it then elongates and invaginates over the umbilical ring.  The body folds (cephalic, caudal, lateral) centrally fuse, where the amnion invests the yolk sac. Defective development at this critical location results in a spectrum of abdominal wall defects. By the sixth week of intrauterine life, rapid growth of the midgut causes it to herniate through the umbilical ring. The abdominal cavity has sufficiently enlarged to accommodate the midgut by the tenth week of life. Rotation and fixation of the duodenal C loop and the proximal colon occur when the intestine returns to the abdominal cavity. Because this process cannot take place in babies with abdominal wall defects, they risk developing midgut volvulus.

Pathogenesis of omphalocele and gastroschisis

Abdominal wall defects result from failure of the mesoderm to replace the body stalk. Embryonic dysplasia, decreased apoptotic cell death, and inadequate mesodermal development result in enlargement of the diameter of the umbilical ring. Rather than investing the yolk sac and body stalk centrally at the umbilicus, the amnion remains attached to the margins of the body wall, creating a persistent communication between the intra-embryonic body cavity and the extra-embryonic coelom.

In babies with omphalocele (see Media file 1, Media file 4), failure of central fusion at the umbilical ring due to defective mesodermal growth causes incomplete closure of the abdominal wall and persistent herniation of the midgut.

Gastroschisis (see Media file 3) may result from the following:

• Defective mesenchymal development at the junction of the body stalk and abdominal wall, resulting in increased abdominal pressure that may cause the dysplastic abdominal wall to rupture.
• Abnormal involution of the right umbilical vein or a vascular accident involving the omphalomesenteric artery may cause localized weakness and subsequent rupture.
• Rupture of a small omphalocele, absorption of the sac, and growth of skin between the resultant opening and the umbilical cord has been chronicled on prenatal ultrasonography.

Pathogenesis of other abdominal wall defects

In hernias of the umbilical cord, the umbilical ring is oversized but the relation of the amnion to the yolk sac and connecting stalk is normal.

Urachal remnants² and omphalomesenteric duct malformations³ result from deficient apoptotic cell death of the epithelium of the urachus and yolk stalk.

Abnormal development of the lower portion of the abdominal wall is caused by defective folding of the embryo's caudal pole and deficient incorporation of yolk sac and allantois in the urogenital sinus; this leads to malformation of the external genitalia.

Bladder exstrophy⁴ (hypogastric omphalocele) occurs in 3.3 per 100,000 births. The bladder develops at 5-9 weeks' gestation, and urine mixes with amniotic fluid by 10 weeks' gestation. The bladder is visible on ultrasonography by the end of the first trimester. Bladder mucosa is soft and pliable at birth, but within 48 hours of exposure, it becomes inflamed and polypoid. Later in life, it may undergo malignant degeneration. Surgical reconstruction to achieve continence, voluntary micturition, and correct vesicoureteral reflux is indicated.

Characteristic findings in bladder exstrophy include the following:

• Anterior vagina and rectum (which may prolapse)
• Epispadias, bifid clitoris, penis, or scrotum
• Dorsal chordee
• Poor urinary sphincter control
• Waddling gait due to outward and downward rotation of the anterior pelvic ring and pubic symphysis diastasis

Prune-belly syndrome is caused by increased apoptotic cell death in the body-wall placode (see Media files 16-17);⁵ this leads to insufficient deposition of mesodermal cells and retention of an abnormally large amount of yolk sac with attenuation of the abdominal musculature.

• Bladder exstrophy with a central strip of everted intestine
• Duplicated colon and appendix, colonic atresia, or imperforate anus
• Sacral and neurologic anomalies, such as myelomeningocele, hydromyelia, and diastematomyelia

Frequency

United States

The combined incidence of omphalocele and gastroschisis is 1 case per 2000 births. Epidemiologic data compiled over the last 40 years show that the incidence of omphalocele has remained constant and is associated with increased maternal age. An inherited predilection is indicated by its occurrence in twins, in consecutive children, and in different generations of the same family.

The incidence of gastroschisis is increasing and is associated with young maternal age and low gravidity. Prematurity and low birth weights, secondary to in utero growth retardation, are commonly seen in babies with gastroschisis.⁷

International

In Japan, the incidence of gastroschisis increased from 0.131 cases per 10,000 births from 1975-1980 to 0.467 cases per 10,000 births from 1996-1997; the incidence of omphalocele increased from 0.322 cases per 10,000 births from 1975-1980 to 0.626 per 10,000 births in 1996-1997⁸ In England and Wales, the incidence of gastroschisis doubled from 1.13 cases per 10,000 births in 1987 to 1.35 per 10,000 births in 1991; the incidence of omphalocele decreased from 1.13 cases per 10,000 births in 1987 to 0.77 per 10,000 births in 1991.⁹ Incidence is also rising in New Zealand.¹⁰

Mortality/Morbidity

The prognosis of babies with gastroschisis and omphalocele continues to improve; survival has increased from 60% during the 1960s to more than 90% currently. Many improvements in the care of premature and low birth weight babies have occurred during this time, particularly in the management of babies with gastroschisis, who have open abdominal wounds with extruded intestine; these babies are especially prone to hypothermia, dehydration, sepsis, and hypoglycemia. Anesthetic management and surgical technique have also improved, as has the ability to provide parenteral nutrition for patients with GI dysfunction.^11,8,9

Long-term morbidity from gastroschisis is related to intestinal dysfunction (including gastroesophageal reflux) and difficulties obtaining wound closure.^12,13,14,15  

Numerous scenarios may result in short-gut syndrome; an antenatal mesenteric vascular accident or constriction of the mesentery of the extruded intestine by a small abdominal wall defect may cause intestinal atresia and diminished absorptive capacity of the gut. Loss of intestinal length exacerbates the dysfunction consequent to antenatal exposure of the intestine to amniotic fluid. An excessively tight closure of the abdominal wall defect may impede splanchnic blood flow and result in intestinal ischemia or necrosis; strangulation infarction may occur consequent to closed loop obstruction from volvulus of the midgut (malrotation) or a single loop that rotates around an adhesion.¹⁶

The care of babies with short-gut syndrome has substantially improved due to innovations in parenteral and enteral nutrition, improved venous access devices, early treatment of catheter sepsis, innovative surgical procedures to optimize gut length, and aggressive treatment of bacterial overgrowth, which occurs in stagnant loops of intestine. However, babies with short-gut syndrome from gastroschisis account for a substantial number of the children undergoing intestinal transplantation.^17,18

Poor healing of the abdominal wound usually results in a ventral hernia, which may require secondary surgical repair. Paradoxically, babies with small omphaloceles have associated abnormalities more frequently, including intestinal problems (eg, Meckel diverticulum, intestinal atresia), genetic syndromes (eg, Beckwith-Wiedemann, trisomy 18), and congenital heart disease.

Babies with giant omphaloceles usually have small, bell-shaped thoracic cavities and minimal pulmonary reserve. Repair of the omphalocele may precipitate respiratory failure, which may be chronic and require a tracheotomy and long-term ventilator support. The authors recently noted a baby with a giant omphalocele and a diaphragmatic hernia. Both conditions are associated with pulmonary hypoplasia, and, when they occur together, the severity of the pulmonary deficit precludes survival, even with the addition of extracorporeal membrane oxygenation (ECMO) support.

Even with successful repair of a giant omphalocele, the liver remains located in the mid epigastrium, lacking the normal protection afforded by the lower rib cage; hence, it is more vulnerable to injury.

Race

Neither gastroschisis nor omphalocele has a geographic or racial predilection.

Sex

The male-to-female ratio is 1.5:1.

Clinical

History

• Infants with gastroschisis and omphalocele can be identified by prenatal ultrasonography.¹⁹
• Defects in other organ systems may also be diagnosed, and chromosomal abnormalities may be discovered by amniocentesis.
• See Work-up.

Physical

• Omphalocele
  • In an omphalocele, the diameter of the abdominal wall defect is 4-12 cm; it may be centrally located or in the epigastrium or the hypogastrium.
  • Surgical repair is easily accomplished if the liver is located within the abdominal cavity; however, even a baby with a small omphalocele may have a complicated clinical course because of associated genetic syndromes with involvement of other organ systems.
  • With a large omphalocele, dystocia may occur and result in injury to the baby's liver; hence, cesarean delivery may be indicated.
  • The omphalocele sac is ruptured in 10-20% of cases; rupture may occur in utero or during delivery.
  • Babies with the Beckwith-Wiedemann syndrome (ie, exomphalos, macroglossia, and gigantism) have coarse, rounded facial features; hyperplasia of the pancreatic islet cells with hypoglycemia; visceromegaly; and genitourinary abnormalities (see Media file 7). Their incidence of developing Wilms tumors and liver tumors (hepatoblastoma) and adrenocortical neoplasms is also increased. Surveillance ultrasonography is indicated.
    
    

    

    Note the enlarged tongue in this baby with Beckwith-Wiedemann syndrome.

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    Note the enlarged tongue in this baby with Beckwith-Wiedemann syndrome.

  • The components of the pentalogy of Cantrell include epigastric omphalocele, cleft sternum, anterior diaphragmatic hernia (Morgagni), absent pericardium, and cardiac defects (ectopia cordis and ventricular septal defects). See Media file 8.
    
    

    

    Baby with pentalogy of Cantrell.

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    Baby with pentalogy of Cantrell.

  • Babies with giant omphaloceles have large, centrally located abdominal wall defects. The liver is ectopic, located outside the abdominal cavity, within the omphalocele sac. The abdominal and thoracic cavities are small and undeveloped. Restrictive lung disease and pulmonary hypoplasia are associated with the thoracic cavity's diminutive size. Operative closure is best accomplished in stages to avoid generating excessive intra-abdominal pressure.²⁰
• Gastroschisis
  • The abdominal wall defect is fairly uniform in size (£ 5 cm) and location (to the right of the umbilical cord).
  • The amount of inflammation, edema and turgor of the intestines, as well as the size of the abdominal cavity, determines whether reduction of the extruded intestine and closure of the abdominal wall can be accomplished. Inflammation may so distort the appearance of the bowel that it may be difficult to determine if associated intestinal atresia is present (see Media files 5-6).
    
    

    

    Baby with gastroschisis and associated intestinal atresia.

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    Baby with gastroschisis and associated intestinal atresia.

    
    
    

    

    Baby with gastroschisis and colon atresia. Bulbous proximal end of the atretic colon is excised, and a colostomy is created at the abdominal wall defect. An anastomosis of the proximal, dilated colon to the distal microcolon (in view of its small caliber) would not function properly. The colostomy can be closed 4-6 weeks later. (Gastrostomy tubes are no longer routinely used.)

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    Baby with gastroschisis and colon atresia. Bulbous proximal end of the atretic colon is excised, and a colostomy is created at the abdominal wall defect. An anastomosis of the proximal, dilated colon to the distal microcolon (in view of its small caliber) would not function properly. The colostomy can be closed 4-6 weeks later. (Gastrostomy tubes are no longer routinely used.)

  • Primary closure of the abdominal wall defect is not possible when the intestines are inflamed, matted together, and turgid. A silo is created to contain the intestine until the inflammation has resolved and it softens and becomes pliable; then reduction can be accomplished. Correction of an associated intestinal atresia is best delayed until several weeks after closure of the abdominal cavity, usually with creation of an enterostomy.
  • Intestinal dysfunction may take as long as 4-6 weeks to resolve.
  • When gastroschisis is identified antenatally, serial ultrasonography is performed to identify impending threats to the intestine; amniocentesis is used to monitor lung maturity and determine when to induce labor.^{21,7,22,23,24}

Causes

• Maternal illness or infection, use of drugs or smoking, and genetic abnormalities are associated with the birth of premature and small-for-gestational-age babies, among whom gastroschisis and omphalocele most commonly occur. These factors may exert their deleterious effect by causing placental insufficiency.¹⁵
• Folic acid deficiency, hypoxia, and salicylates cause rats to develop abdominal wall defects, but the clinical significance of these experiments is conjectural.
• Elevation of maternal serum alpha-fetoprotein (MSAFP) levels warrants ultrasonography to determine if structural abnormalities are present in the fetus. If the study is suspicious for an omphalocele, amniocentesis is indicated to determine any associated genetic abnormality.
• Because polyhydramnios occurs in association with fetal intestinal atresia, it should prompt an expeditious investigation with ultrasonography and referral to a tertiary care facility, where the newborn can receive surgical care.

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