Historical Background

Omphalocele was first described by Ambrose Paré during the 16th century, with emphasis on the critical nature and poor prognosis of this condition; gastroschisis was likely described by Lycosthenes near the same time. The present day classifications were established in 1953 by Moore and Stokes, who described omphalocele and gastroschisis by distinguishing the location of the umbilical cord, the presence or absence of a covering sac, and the appearance of eviscerated bowel ( Table 58-1 ).

Early management strategies for omphalocele consisted of the use of various topical regimens, as well as skin flap closure techniques. Olshausen described the first surgical intervention for omphalocele in 1887 with skin flap coverage. Nonoperative management was first described by Ahlfeld in 1899, utilizing the application of alcohol on the sac to induce eschar formation with subsequent contraction and epithelialization. Due to difficulty performing staged closure, Gross described a surgical procedure in 1948 in which he closed the skin over an intact omphalocele sac. However, skin flap closures often resulted in large and difficult-to-repair ventral hernias that necessitated further surgical intervention. Additional nonoperative management was later proposed by Ein and Shandling, who employed a skin-like polymer membrane to induce granulation of the sac surface. However, this technique also resulted in the need for eventual closure of a large complex ventral hernia.

The first report of a successful surgical gastroschisis repair was by Watkins in 1943, who enlarged the existing defect, returned the viscera to the abdominal cavity and applied sulfanilamide crystals, and closed with interrupted sutures. Although ultimately unsuccessful, Moore and Stokes adopted Gross’ skin flap technique in 1953 in an attempt to repair the defect in two patients with gastroschisis. These infants experienced abdominal compartment syndrome and acute respiratory insufficiency. To address these issues and decrease intraabdominal volume, subsequent surgeons performed partial hepatectomy, splenectomy, and bowel resection, with a resultant high mortality rate.

In 1967, Schuster described a new surgical technique that was applicable to both omphalocele and gastroschisis, and that would eventually revolutionize the management of neonatal abdominal wall defects. By attaching prosthetic material to the abdominal fascia at the lateral edges of the defect and suturing the mesh together under tension, intraabdominal forces were altered to favor gradual enlargement of the abdominal cavity. Periodic reopening of the abdomen with serial reduction and staged removal of the mesh was subsequently performed. In 1968, Gilbert reported a modification of the afore­mentioned technique, utilizing reinforced silicone sheets sutured to the fascia and left to exit the wound. In 1969, Allen and Wrenn used these silicone sheets to construct a silo around the eviscerated bowel, and gradually, the silo was reduced until the fascia could be closed. The addition of the silo method to the surgeon’s armamentarium provided an important tool for the management of neonatal abdominal wall defects, as serial reduction with delayed closure of gastroschisis and staged closure of omphalocele are commonly utilized approaches today.

Despite successful surgical intervention, many infants during the early era died of nutritional deficiencies resulting from prolonged ileus. In 1969, Filler reported on the use of total parenteral nutrition (TPN) for infants with abdominal wall defects. TPN use altered the postoperative course for these patients to allow for adequate nutrition while recovering from surgical intervention.

Embryogenesis

Etiology

The cause of abdominal wall defects in newborns is unknown. Traditionally, gastroschisis has been associated with young maternal age and the presence of teratogenic factors. In contrast, omphalocele has been associated with advanced maternal age, as well as genetic and familial factors. Animal models have explored the role of teratogens, with experimental induction of both gastroschisis and omphalocele.

Review of clinically based literature implicates low socioeconomic status, poor prenatal care, and poor nutrition, specifically, low levels of glutathione and α-carotene and high levels of nitrosamines, in the development of gastroschisis. The use of vasoconstrictive medications, including pseudoephedrine and phenylpropanolamine, is associated with an increased risk of gastroschisis. Maternal smoking and use of illegal substances, such as cocaine and methamphetamine, during pregnancy are additional risk factors.

The risk factors identified for omphalocele also involve poor nutrition and lifestyle, including vitamin B ₁₂ and folic acid deficiency, as well as poor glycemic control. Periconceptional use of multivitamins has been reported to reduce the incidence of nonsyndromic omphalocele by 68% in one population-based study. The use of selective serotonin reuptake inhibitors has also been associated with an increased risk of omphalocele. Other studies have identified maternal febrile illness and in vitro fertilization as risk factors. Omphaloceles are associated with chromosomal anomalies, including trisomy 13, 18, and 21, with trisomy 18 being the most common. In the rare event of familial or syndromic cases, obtaining a complete family history enables the physician to provide appropriate recurrence risk counseling.

The Evolution of Epidemiology

The Centers for Disease Control and Prevention reports the incidence of omphalocele as approximately 1 in 5,000 live births, whereas gastroschisis is more common, with an incidence of approximately 1 in 2,000 live births. Although the incidence of omphalocele has remained unchanged, the incidence of gastroschisis continues to increase. An increasing prevalence of gastroschisis has been documented in the United States, and an increasing incidence has been noted in Spain and in New Zealand.

The incidence of gastroschisis increases with young maternal age and low gravidity. Although both gastroschisis and omphalocele are associated with prematurity and lower birth weight, prematurity is more common in newborns with gastroschisis. Furthermore, infants with gastroschisis are often smaller than omphalocele newborns.

The male-to-female ratio is 1.5:1 for omphalocele, but no gender differences exist for gastroschisis. No racial or geographic associations have been observed for gastroschisis or omphalocele. Omphaloceles are more likely to have a familial recurrence and have been reported in consecutive children, twins, and different generations of the same family.

A Spectrum of Defects

Omphalocele

The midline umbilical ring defect characterizing omphaloceles can range from small and easily treatable to a very large mass (giant omphalocele) containing multiple abdominal viscera. Historically, the congenital hernia of the umbilical cord (CHUC) has been miscategorized as an omphalocele, but the CHUC differs in that it is characterized by an intact abdominal wall and a complete umbilical ring. It is notable that in neonates with CHUC, only a few loops of small bowel may be herniated, and iatrogenic injury can occur at the time of cord clamping. The abdominal wall defect of the omphalocele varies in size from 4 to 12 cm. The eviscerated contents are contained in a sac, comprising peritoneum and amnion, which together forms a translucent, avascular membrane ( Figure 58-1 ). The umbilical cord inserts directly onto the sac. The omphalocele sac usually contains stomach, small bowel loops, colon, and liver. With a small defect, the contents are easily reduced, allowing for simple surgical closure. In cases of giant omphaloceles, the bladder, gonads, and spleen may also be contained in the sac, and the peritoneal cavity is extremely small and underdeveloped. Such cases present the greatest challenge in management and are associated with higher morbidity.

Neonate born with an omphalocele with a large abdominal wall defect. The omphalocele sac is intact, and the umbilical cord inserts directly onto it.

Gastroschisis

The abdominal wall defect in gastroschisis is generally 5 cm or less and located to the right of the umbilical cord. Rare cases of left-sided gastroschisis have been reported. Furthermore, the gastroschisis defect is full-thickness. Herniated abdominal contents typically include only the small bowel, but may include colon, stomach, gallbladder, uterus, fallopian tubes, urinary bladder, and gonads. The extruded intestines are often covered by an inflammatory peel and have an abnormal, matted appearance, but no sac exists ( Figure 58-2 ). Incarceration of the protruding organs can occur at any point during fetal development or after delivery. The abdominal musculature is normally developed. The abdominal cavity, although underdeveloped, tends to be larger than that seen in omphaloceles. No genetic mutations or chromosomal abnormalities have been discovered in association with gastroschisis, with the exception of a case report of gastroschisis associated with Turner syndrome. Associated anomalies are rare, except for an increased incidence of intestinal atresia.

Neonate born with gastroschisis with small bowel and colon protruding through the defect. The abdominal wall defect is to the right of the umbilical cord.

Clinical differences between omphalocele and gastroschisis are summarized in Table 58-1 .

Associated Anomalies

Omphalocele may be associated with chromosomal abnormalities. Trisomy 13 and 18 are the most commonly found abnormalities in these neonates. Associations with trisomy 21 have also been reported. Small omphaloceles without liver herniation are more commonly associated with chromosomal abnormalities.

Omphaloceles with accompanying congenital anomalies are associated with a higher mortality rate. A constellation of defects can be seen in patients with omphalocele. In Beckwith-Wiedemann syndrome, infants present with macroglossia, large and rounded facies, visceromegaly, hypoglycemia, and kidney anomalies in addition to omphalocele. The pentalogy of Cantrell consists of five characteristic findings: epigastric omphalocele, anterior diaphragmatic hernia, distal sternal cleft, pericardial defects, and congenital heart disease—in some cases, ectopia cordis may also be present. Congenital heart disease and cardiac defects are the most common structural anomaly (approximately 20%) in newborns with omphalocele and include tetralogy of Fallot, ventricular septal defects, atrial septal defects, and persistent pulmonary hypertension. In addition, genitourinary anomalies may be associated with omphaloceles in conditions such as OEIS complex (omphalocele, exstrophy, imperforate anus, spinal defects). Additional anomalies found with omphalocele include musculoskeletal abnormalities, cleft palate, and prune belly syndrome. It is notable that the presence of pulmonary hypoplasia, seen commonly in infants with giant omphalocele, portends a poor prognosis.

Intestinal tract abnormalities are present in both omphalocele and gastroschisis, as malrotation is seen in both types of abdominal wall defects. An increased risk of midgut volvulus exists due to a lack of intestinal fixation and a narrow mesentery. Following surgical repair of an abdominal wall defect, postoperative adhesions significantly decrease the risk of volvulus. Intestinal atresia occurs in 10% to 20% of cases of gastroschisis, with the most common location being jejunoileal. Gastroschisis may also be complicated by short bowel syndrome and intestinal dysfunction, including dysmotility and impaired absorption. The eviscerated intestine in gastroschisis is often inflamed, matted, edematous, thickened, and exudative. Studies have demonstrated decreased fat, protein, and carbohydrate absorption in neonates with gastroschisis; however, transit time and absorption patterns typically return to normal by 6 months. The proposed etiologies for abnormal gastrointestinal function of the compromised intestine include length of time exposed to amniotic fluid, alterations in the amniotic fluid composition, and changes in blood flow, which may explain the increased severity of dysfunction in cases of gastroschisis as compared to omphalocele. Intestinal compression at the site of the defect results in edema and ischemic changes, increasing the risk of inflammation and perforation. In a fetal lamb model, placement of a ligature around the herniated bowel to cause constriction led to bowel dysmotility. Intestinal damage and dysfunction is the most common abnormality seen in the setting of gastroschisis.

Prenatal Management

The diagnosis of gastroschisis and omphalocele is usually made on antenatal ultrasound. Prenatal diagnosis allows for risk assessment, parental counseling, and discussion of pregnancy termination, as well as optimization of management including timing, location, and method of delivery. In the setting of associated severe anomalies or life-threatening comorbidities with a known abdominal wall defect, moral, religious, and ethical questions and discussions may affect the course of the pregnancy. It is critical that the parents are counseled by a multidisciplinary team, as such decisions are extremely difficult. Although useful for parental counseling and planning, previous studies failed to show the impact of antenatal diagnosis of abdominal wall defects on infant outcomes, including birth weight, gestational age at birth, time to full feeding, need for ventilator support, length of stay, or mortality. However, a multidisciplinary approach to prenatal care, including involvement of a pediatric surgeon, neonatologist, and obstetrician, may facilitate term delivery. Education of the family, including pictures and likely course of management, can help prepare expecting parents and address anxiety.

Imaging

Ultrasound imaging is the mainstay for diagnosis and monitoring of unborn infants with abdominal wall defects. Infants with omphalocele are distinguished from gastroschisis by the presence of a sac and by the presence of the liver within the defect. In gastroschisis, free-floating loops of bowel are typically evident in the amniotic fluid. Ultrasound is also useful in the detection of associated anomalies, including intestinal atresia and cardiac anomalies. Given the associated risk of cardiac anomalies, fetal echocardiograms should be performed in the setting of abdominal wall defects. Serial ultrasonography should be performed to detect intrauterine growth retardation, oligohydramnios or polyhydramnios, and signs of bowel obstruction or damage. Although previously thought to predict postnatal complications, isolated findings of gastrointestinal abnormalities on prenatal ultrasound have not been shown to correlate with adverse outcomes.

Magnetic resonance imaging (MRI) is also used to assess a fetus for abdominal wall defects, particularly when ultrasound findings are subtle or inconclusive. It may be used as an adjunct to evaluate prognostic factors, such as abnormal appearance of the bowel, polyhydramnios, and associated fetal developmental abnormalities. Various fast-scan MRI imaging techniques have been developed to image the fetus, with attention to decreasing image degradation caused by fetal motion. In the presence of gastroschisis, MRI demonstrates herniated bowel loops floating freely in amniotic fluid, distinguishes bowel signal from the umbilical cord, and demonstrates the position of the defect to the right of the normal umbilical cord insertion ( Figure 58-3A,B ). An omphalocele can be delineated on MRI based on the ability to detect a mass consisting of herniated viscera, including liver, stomach, small bowel, colon, or spleen, covered by a sac ( Figure 58-4 ). However, in the presence of a ruptured omphalocele, which lacks the peritoneal-amniotic membrane sac, bowel floats freely, making this condition difficult to distinguish from gastroschisis. Compared to ultrasound imaging, the presence of abdominal contents and the location of the defect can be better identified on MRI, helping to determine the underlying pathology.

(A) Sagittal MRI gradient echo sequence of a fetus with gastroschisis. Numerous bowel loops (arrow) are seen herniating through a small defect and are free-floating outside the abdomen. (B) Axial MRI gradient echo sequence of the same fetus. The small abdominal wall defect (arrowhead) lies to the right of the normal umbilical cord (arrow) insertion. The herniated bowel is dark on this sequence at the level of the defect, while the umbilical cord is bright. There is no sac covering the bowel.

(Courtesy of Carl Merrow, MD.)

Sagittal MRI gradient echo sequence showing a giant omphalocele in a 34-week gestation fetus with fluid (asterisk) distending the sac (arrow) around the liver (L) and dilated bowel (B).

(Courtesy of Carl Merrow, MD.)

Obstetric Delivery

Historically, controversy over the mode of delivery for fetuses with abdominal wall defects has existed. Proponents of elective cesarean section for prenatally diagnosed omphalocele focused on large defects with visceral contents, which could cause obstructed labor or liver injury, or tearing of the sac. Those in favor of cesarean section for gastroschisis patients were concerned about injury to exposed bowel and vasculature. Reported benefits of cesarean section in the setting of gastroschisis included decreased intestinal edema and easier to repair defects with shorter hospital stays and lower mortality. However, recent obstetric literature, including large retrospective reviews and a comprehensive meta-analysis, does not support the routine use of cesarean section. Mode of delivery should be determined by obstetric indication irrespective of the presence of abdominal wall defects.

Timing of delivery for fetuses with abdominal wall defects is also controversial. Because bowel edema and the occurrence of an inflammatory peel increase in gastroschisis with the progression of pregnancy, some advocate early delivery. However, studies examining the indications for preterm delivery have demonstrated no benefit, including no decrease in hospital length of stay with preterm delivery. In addition, adverse outcomes, including higher rates of sepsis, longer time on parenteral nutrition, longer time to achievement of full enteral feeds, and longer length of stay were seen in early delivery of gastroschisis infants. Currently there is no role for preterm delivery for fetuses with omphalocele.

Immediate Postnatal Management

Following delivery, resuscitation should begin immediately with placement of intravenous access, gastric decompression to prevent vomiting and aspiration, and assessment of cardiopulmonary status. Signs of respiratory distress necessitate immediate endotracheal intubation with ventilator support and supplemental oxygen. Intravenous lines should be preferentially placed in the upper limbs due to possible inferior vena cava compression during bowel reduction. Laboratory values, including hematocrit, serum electrolytes, blood glucose, and arterial blood gas, should be obtained soon after birth and used to guide resuscitation. In the presence of gastroschisis, strict monitoring of serum glucose levels are indicated, as associated prematurity and intrauterine growth retardation increase the risk for hypoglycemia. A nasogastric or orogastric tube is placed to decompress the stomach and decrease intestinal distension, which may facilitate visceral reduction.

Herniated bowel should be addressed and managed early to prevent ongoing fluid losses and hypothermia. The omphalocele sac should be left intact but wrapped with saline-soaked gauze and an impervious dressing to minimize fluid losses and risk of hypothermia. In the presence of gastroschisis with eviscerated bowel or a ruptured omphalocele, the bowel should be wrapped in saline-soaked gauze and placed in a central position, with the infant placed on the right side to prevent vascular compromise due to mesenteric kinking. The bowel is then wrapped in an impervious dressing, such as plastic wrap. As an alternative to wrapping with saline-soaked gauze and an impervious dressing, the neonate’s lower extremities and torso may be placed in a bowel bag with drawstring up to the level of the chest to reduce significant ongoing evaporative losses ( Figure 58-5 ). If the gastroschisis defect is small and vascular compromise of the bowel is detected, immediate enlargement of the defect is crucial to restore adequate blood flow. In addition, the intestine may require untwisting to restore circulation. Infants should be placed under a radiant heater or in a heated incubator to maintain core body temperature.

Neonate with gastroschisis who was transported with lower extremities and torso secured in a bowel bag with drawstring.

After initial resuscitation, a thorough examination should be performed to establish the presence of associated anomalies. In gastroschisis, the bowel should be inspected for atresia, necrosis, or perforation. Initial management of omphalocele, as outlined earlier, should be performed while the cardiopulmonary status is carefully assessed. Infants with omphalocele may have pulmonary hypoplasia or pulmonary hypertension. A directed car­diac evaluation including physical examination and chest radiograph is needed to detect associated anomalies. Echocardiography is warranted in the presence of abnormal clinical or radiographic findings. Abdominal ultrasonography should be performed to detect renal anomalies. In the presence of neonatal hypoglycemia, the infant should be evaluated for Beckwith-Wiedemann syndrome. A rectal examination is necessary to assess patency and aide in the evacuation of meconium.

Infants with abdominal wall defects experience excessive fluid losses and electrolyte imbalances. Ongoing resuscitation, especially in the setting of gastroschisis or ruptured omphalocele, is critical and must be begun prior to transfer to a tertiary referral center. Clinical parameters used to guide fluid resuscitation are heart rate, mean arterial blood pressure, and urine output. Infusion of 5% dextrose/0.45 normal saline at two to three times maintenance requirements is often necessary. Electrolytes should be replaced as dictated by serum chemistry panels.

Transfer of infants with abdominal wall defects to an appropriate tertiary care center is recommended after initial stabilization for definitive operative management and postoperative expertise. If trisomy 13 or 18 is confirmed, prognosis is poor. A discussion with the family should address the indications for treatment in the face of likely demise.

Surgical Management

Surgical Management of Gastroschisis

The primary goal of the surgical management of gastroschisis is the return of the bowel into the abdomen without jeopardizing the viscera, which can occur through direct trauma or creation of abdominal compartment syndrome and subsequent ischemia. The first step after adequate resuscitation is close inspection of the intestine for atresia, necrosis, obstructing bands, or vascular compromise. Obvious obstructing bands should be divided to prevent bowel obstruction. The inflammatory peel, which often covers the bowel in gastroschisis, should not be removed due to risk of intestinal perforation. If a very small abdominal defect is identified causing vascular compromise to the bowel, the fascial defect should immediately be enlarged, either to the right or superiorly to the left avoiding the umbilical vein. To address the abdominal wall defect, several management strategies are employed in the surgical repair of gastroschisis and vary according to the size of the defect, amount of exposed bowel, size of the neonate, and presence of comorbidities. Surgical options for gastroschisis include primary reduction and fascial closure, silo placement with serial reduction and delayed fascial closure, or primary or delayed reduction without fascial closure. Central venous access should be established for parenteral nutrition due to the presence of underlying intestinal dysmotility.

Primary reduction and fascial closure was historically favored based on retrospective reviews demonstrating improved outcomes. Several studies demonstrated that infants able to undergo immediate primary reduction and fascial closure have shorter courses of parenteral nutrition, less time on the ventilator, and a shorter length of stay when compared to those undergoing staged or delayed closure. Although selection bias confounded the results of most of these studies, if little bowel is exposed and intraabdominal domain appears adequate, primary reduction and fascial closure may be performed. The intraabdominal domain can be increased modestly by stretching of the abdominal wall. Intestinal loops are returned to the abdominal cavity, ensuring that the mesentery is not twisted, and fascia is approximated using interrupted sutures. Several skin and wound closure techniques are described later.

When primary reduction cannot be accomplished, silo placement with serial reductions and delayed fascial closure is utilized. The silo method using Silastic sheets sewn together and sutured to the abdominal wall was first described by Allen and Wrenn in 1969. The silo covers the exposed bowel to minimize evaporative losses and prevent additional trauma while allowing for direct inspection of bowel perfusion and slow reduction into the abdomen. Newer manufactured Silastic silos with a circular spring now exist that can be placed at bedside without need for sutures or anesthesia ( Figure 58-6A,B,C ). To keep the silo perpendicular to the abdominal wall defect, the top of the silo is tied to an overhead bar ( Figure 58-6D ). The base of the silo is kept wrapped with betadine-soaked sterile gauze to prevent evaporative fluid losses and contamination. As spontaneous diuresis decreases bowel wall edema, gravity pulls the bowel back into the abdomen. In addition, bowel is reduced into the abdominal cavity by sequential shortening and ligation of the silo one to two times daily. Methods for silo shortening and ligation include the use of a specially designed wringer clamp with a guard to keep the Silastic sheet approximated while pushing down the bowel, or more commonly, the use of umbilical tape tied around the prefashioned spring-loaded Silastic silo ( Figure 58-7 ). Once complete reduction or a plateau of reduction has been obtained ( Figure 58-8 ), a process that usually takes approximately 5 to 7 days depending on the con­dition of the bowel and the infant, fascial closure is attempted.

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