What Are the Differences Between Gastroschisis and Omphalocele?

Gastroschisis and omphalocele are the most common congenital abdominal wall defects with a prevalence of approximately 1:2,000–1:5,000 live births in the United States. Although each represents a distinct anatomical defect, their anesthetic considerations are the same. Each is a congenital defect that allows a portion of the intestinal viscera to extrude outside the abdominal cavity and both require surgical repair in the newborn period (Figure 2.1). Large defects are managed with a staged approach if primary closure is not possible.

Figure 2.1 Omphalocele prior to surgery.

Photograph: Ronald S. Litman, reproduced with parental permission.

An omphalocele occurs when the visceral organs fail to migrate from the yolk sac back into the abdomen early in gestation and the umbilical ring remains open; the defect is a central lesion and occurs at the insertion of the umbilicus. Gastroschisis is thought to result from an occlusion of the omphalomesenteric artery during early development. As a result, the abdominal viscera herniate through a rent in the abdominal wall, usually to the right of the umbilicus. Omphalocele is more likely than gastroschisis to be associated with additional congenital defects. These occur in 25–50% of cases and include chromosome anomalies and cardiac defects. Omphalocele may be a component of the Beckwith–Wiedemann syndrome, which consists of hypertrophy of multiple organs. This syndrome is particularly relevant to the anesthesiologist as enlargement of the tongue may compromise the upper airway and be associated with difficult intubation. Pancreatic enlargement causes hyperinsulinism, which results in hypoglycemia and needs to be monitored intraoperatively. The key characteristic differences are summarized in Table 2.1.

Infants with gastroschisis are usually born at full term without additional isolated defects. The major pathophysiological difference between the two is that, in omphalocele, the intestinal contents remain covered with the peritoneal membrane, which protects the intestinal mucosa from the irritative effects of amniotic fluid and protects the infant from excessive evaporative fluid and temperature loss after delivery. Infants with gastroschisis lack this natural protective covering, and thus are more prone to dehydration, hypoglycemia, hypothermia, third-space fluid accumulation, electrolyte imbalance, acidosis, bleeding, and sepsis.

Management of omphalocele or gastroschisis begins immediately after birth. The extruded abdominal contents are covered with warm saline dressings and are encased in a sterile plastic bag or wrap to decrease fluid and temperature loss and discourage infection (Figure 2.2). A naso- or orogastric tube is placed for gastric decompression, normovolemia is maintained with intravenous hydration, and associated comorbidities are addressed prior to surgical repair. Antibiotics may be necessary if intestinal abnormalities are suspected.

Figure 2.2 Omphalocele silo. Large omphaloceles are treated with a silo and progressive constriction until primary repair.

Photograph: Ronald S. Litman, reproduced with parental permission.

Achieving a primary repair is the goal of surgery as failure to replace all of the intestinal contents back into the abdominal cavity increases postoperative morbidity. However, in many cases where the abdominal cavity is too restrictive or when there is not enough skin to close the underlying defect, a partial replacement is performed, and the remaining external viscera are encased in a synthetic silo mesh allowing for complete repair to occur as a staged procedure.

In addition to its impact on intrathoracic pressure, increased intra-abdominal pressure may result in an abdominal compartment syndrome. When this occurs, venous compression leads to a decrease in preload and hypotension as well as lower limb venous congestion. High intra-abdominal pressures may lead to renal artery compression resulting in oliguria as well as decreased perfusion to the lower extremities. Bowel ischemia may also result, secondary to decreased perfusion. Adequate volume and blood replacement and full neuromuscular blockade must be maintained throughout the procedure to optimize the chances for successful primary closure.

What Are the Risks and Benefits of Staged Versus Primary Abdominal Wall Closure?

The optimal surgical management is related to the degree of bowel extrusion and the ability of the abdominal cavity to accept bowel replacement. Infants undergoing primary closure generally require a shorter length of hospitalization and decreased utilization of parenteral nutrition.

Secondary closure techniques have evolved over the past few decades. The extruded bowel is maintained in a spring-loaded silo bag. The bag keeps the bowel intact and protected from environmental contact. This mechanism allows for daily bedside reduction of the bowel over one to two weeks providing time for the abdominal cavity to expand and accommodate without elevating abdominal pressures and interfering with ventilation.

What Are the Anesthetic Considerations for Surgical Intervention of Patients with Gastroschisis or Omphalocele?

Considerations for induction of general anesthesia are similar to those for any newborn infant with a presumed increased risk of a “full stomach” secondary to intestinal obstruction. A modified rapid sequence intubation (RSI) is performed using gentle breaths. Some pediatric anesthesiologists will prefer to temporarily remove the nasogastric tube during induction to facilitate airway management.

There are several intraoperative adverse physiologic derangements that may occur when the surgeon attempts to place a large volume of abdominal contents back into a small, restrictive abdominal cavity. Cephalad displacement of the diaphragm due to the increase in abdominal contents may significantly decrease functional residual capacity (FRC) and tidal volume, which can lead to difficult ventilation, development of atelectasis, and hypoxemia. During the repair, the anesthetist may frequently need to use manual ventilation to maintain adequate tidal volumes in response to rapid changes in lung compliance. The presence of hypoxemia despite maximal ventilation may preclude completion of a primary repair. Therefore, intraoperative management should focus on ventilatory pressures, temperature regulation, and volume status. Rapidly increasing peak pressures (when using volume-controlled ventilation) or a significant decline in tidal volume (when using pressure-controlled ventilation) should raise suspicion of abdominal pressure elevation that will compete with the ability to provide adequate minute ventilation. Fluid administration, postoperative fluid shifts, and associated bowel edema can lead to increases in abdominal compartment pressure, low cardiac output, and renal hypoperfusion.

These patients are at risk of hypothermia from exposed abdominal contents. Similarly, fluid evaporative losses are common, especially with gastroschisis where the surface of the intestine is uncovered and exposed to the atmosphere.

All infants, except those with the most trivial repairs, remain intubated and mechanically ventilated in the postoperative period. Abdominal compartment syndrome and respiratory compromise may continue postoperatively; therefore, paralysis and adequate sedation with an opioid infusion are essential for optimal management.

What Are the Pertinent Preoperative Diagnostic and Laboratory Evaluations Suggested for These Patients?

The diagnosis of omphalocele should alert the clinician to the possibility of numerous coexisting congenital defects. Intrapartum diagnosis should prompt fetal echocardiography and even postnatal echocardiographic evaluation, as the incidence of concomitant cardiac anomalies is as high as 25%. Pulmonary hypoplasia often necessitating ventilatory support, cloacal exstrophy, and anomalies associated with VACTERL syndrome may be present. Normal karyotype patients have an incidence of other abnormalities that is as high as 80%, stressing the importance of a complete perioperative evaluation. Chromosomal abnormalities (especially trisomies 13, 18, and 21) exist in nearly 50% of patients with omphalocele. Unlike gastroschisis, the herniation in omphalocele patients is enclosed and amenable to supportive therapy while workup is obtained. Intravenous access should be obtained, and fluid resuscitation initiated. Glucose should be evaluated frequently, and if low, it should raise suspicion for Beckwith–Wiedemann syndrome. Careful cardiopulmonary workup should ensue prior to closure in a stable neonate. The bowel should be wrapped to minimize heat and evaporative loss, which, while less extreme compared with gastroschisis patients, remains greater than in patients with a closed abdomen. Naso- or orogastric tubes should be placed for decompression.

The assessment for comorbidities, while less common in patients with gastroschisis, should include evaluation for meningocele, limb abnormalities, and intestinal atresia. Intravenous access and maintenance of fluid homeostasis is vital as well as frequent evaluation of electrolytes. In the interim, exposed bowel should be wrapped with sterile dressing and plastic to minimize infection, evaporative fluid loss, and temperature loss. The bowel should be evaluated frequently for early recognition of ischemic changes possibly due to mesenteric kinking.

What Is the Prognosis for Patients with Gastroschisis and Omphalocele?

The prognosis for omphalocele is related to the number and severity of associated congenital anomalies. The optimal mode and timing of delivery is debated although most neonates with omphalocele are delivered via cesarean section for fear of abdominal sac rupture with labor.

Prognosis for gastroschisis is generally determined by the degree of bowel injury and bowel atresia. Exposure of the bowel to amniotic fluid and degree of bowel constriction dictates the severity of injury. Gastroschisis patients have a greater incidence of developing necrotizing enterocolitis when compared with the general population. The optimal mode and timing of delivery is still debated.

What Is the Beckwith–Wiedemann Syndrome?

The incidence of Beckwith–Wiedemann is approximately 1 in 13,000–14,000 children without gender predominance.

What Is the General Phenotypic Appearance of Children with Beckwith–Wiedemann Syndrome?

Children with Beckwith–Wiedemann syndrome display signs of accelerated growth, including height and weight. Common facial abnormalities include prominent eyes, midfacial hypoplasia, macroglossia or hemihypertrophy, prominent mandible, and earlobe anomalies.

Macroglossia can lead to sleep disordered breathing and sleep apnea. In addition, hemihypertrophy can often pose difficulty with airway management.

What Are the Associated Malformations Found in Patients with Beckwith–Wiedemann Syndrome?

Beckwith–Wiedemann is a disorder of increased growth (somatic overgrowth) with a predisposition to development of embryonal tumors. Malformations include abdominal wall defects and visceromegaly of one or more of the following: heart, liver, spleen, pancreas, kidneys and adrenals. Neonatal hypoglycemia occurs in up to 50% of children with Beckwith–Wiedemann syndrome due to pancreatic islet cell hyperplasia and hyperinsulinemia.

Cardiac anomalies are present in approximately 20% of patients with Beckwith–Wiedemann syndrome. Renal anomalies are common, including medullary dysplasia, nephrocalcinosis, or nephrolithiasis.

Patients with Beckwith–Wiedemann syndrome are predisposed to development of embryonal tumors especially within the first decade of life. Common tumors include Wilms, hepatoblastoma, rhabdomyosarcoma, neuroblastoma, and adrenocortical carcinoma. The risk of tumor development may be greater in children with hemihypertrophy and nephromegaly.