Danielle B. Peterson and Marjorie J. Arca
GASTROSCHISIS
Gastroschisis is congenital abdominal wall defect though which intraperitoneal contents protrude (Fig. 396-1). The defect occurs to the right of the umbilical cord and can range in size from 2 to 5 cm. The most commonly eviscerated organs include the intestines and gonads. Gastroschisis occurs in younger mothers,1 with a total incidence of one in 3000 live births.2 Several studies have reported a recent increase in the incidence of gastroschisis.3-5
PATHOGENESIS
Gastroschisis occurs during the sixth or seventh week of gestation. The right umbilical vein naturally involutes, leaving one umbilical vein and two umbilical arteries. It is hypothesized that the right abdominal wall suffers from vascular compromise, which results in gastroschisis.6,7 Other hypotheses of gastroschisis formation include defective development of the mesenchyme on the anterior abdominal wall and rupture of the omphalocele membrane with subsequent growth of skin surrounding the umbilicus.8
EPIDEMIOLOGY
Maternal and environmental factors have been implicated in the development of gastroschisis. In animal models, folic acid deficiency, maternal hypoxia, and salicylates have been linked to abdominal wall defects.9 The use of vasoconstrictive agents, such as pseudoephedrine, cocaine, and cigarettes, in early pregnancy have been postulated to increase the risk of gastroschisis.10 Other gastroschisis-inducing teratogens include atrazine, a chemical found in pesticides, and possibly maternal use of salicylates or acetaminophen.11,12
Infants with gastroschisis tend to be born prematurely. There is some evidence that gastroschisis infants allowed to deliver after 36 weeks have a stillborn rate of approximately 10%.13 Consequently, mothers of gastroschisis infants are induced to deliver at 36 to 37 weeks, when lung maturity is reached.
Ten percent of infants with gastroschisis have an associated intestinal atresia of varying lengths. It is thought that the atresia results from in utero segmental intestinal volvulus.
The intestines of infants with gastroschisis have an inherent dysmotility. In most gastroschisis infants, the average time to start feeds after abdominal wall closure is 21 days, with the average time to full feeds of approximately 28 days, but the intestinal dysmotility can be prolonged, necessitating the need for parenteral nutrition for months to years.14
The incidence of necrotizing entercolitis after gastroschisis repair can be as high as 18.5% and can occur up to several weeks after abdominal wall closure.15
PRENATAL DIAGNOSIS AND MANAGEMENT
The diagnosis of gastroschisis is usually made using prenatal ultrasound. The accuracy of prenatal screening ultrasound detection of abdominal wall defects ranges from 57% to 95% for gastroschisis.1,2,16Fetal MRI, though gaining in popularity, is usually not necessary.
Maternal serum markers aid in the prenatal diagnosis of abdominal wall defects. On the maternal triple test, α-fetoprotein is elevated in all gastroschisis cases. Acetyl-cholinesterase is also elevated in the amniotic fluid of patients with gastroschisis. Karyotype analysis may be indicated in gastroschisis fetuses that have evidence of additional anomalies.
Current recommendations for the perinatal management of gastroschisis include birth in a facility with immediate pediatric surgical availability. Normal labor and vaginal delivery are encouraged.
MANAGEMENT
At birth, gastroschisis infants lose fluid and body heat due to the large exposed surface area. In addition, the intestines are suspended on a thin, narrow mesenteric pedicle. Measures to decrease heat and temperature loss, decrease kinking of the mesentery and prevent desiccation and ischemia of the exposed viscera are mandatory within minutes after the baby’s birth. This can be accomplished by wrapping the bowel in saline-moistened gauze and then wrapping the infant in clear thermoplastic wrap. The bowel must be supported to prevent vascular compromise. If transport is necessary, it is best accomplished in the lateral position to minimize tethering of the mesentery. Gastric decompression and venous access should be secured. Appropriate fluid resuscitation is required to maintain adequate urine output and acid-base balance. Antibiotics should be started.
The goal of surgical treatment for gastroschisis is ultimate closure of the muscle, fascia, and skin; this will confer the greatest chance of survival and least morbidity. Most centers perform definitive closure in the operating room under general anesthesia. Primary fascial and skin closure are possible in one half to two thirds of patients.
Closure of the abdomen may be complicated by abdominal compartment syndrome, necessitating a staged reduction. If staged reduction is necessary, a silo is placed over the intestines. Gradual reduction is performed daily for 7 to 10 days, allowing the abdominal domain to slowly enlarge. If intestinal atresia is present, repair of the atresia is deferred for 6 weeks from fascial closure to allow for resolution of intestinal serositis.
FIGURE 396-1. Infant with gastroschisis.
OUTCOMES
Simple gastroschisis is an isolated abdominal wall defect that occurs in 89% of all gastroschisis patients with an all-cause mortality of 3%.22 Complex gastroschisis is associated with other gastrointestinal anomalies such as intestinal atresia, perforation, necrosis, or volvulus and has a reported mortality rate of 9%.22
Most centers report a 50% to 80% primary closure rate for gastroschisis. The average length of mechanical ventilation was 5.7 days, with an average length of initial hospitalization of 66 days. Complications occurred in 70% of children, with the most common complications including ileus (28%), catheter infection (25%), and sepsis (15%). Thirty-eight percent of children required reoperation during the initial hospitalization. One half required rehospitalization, and 35% required further operations beyond the initial hospitalization.
All infants with gastroschisis have intestinal nonrotation. A formal Ladd procedure is not performed with a primary or a staged closure. Parents are warned that infants with gastroschisis can have bowel obstruction secondary to adhesions or less commonly volvulus, for the rest of their lives.
At long-term follow-up, only 7.1% of gastroschisis patients report frequent gastrointestinal problems. Most parents described the cosmetic and physiologic results as good or excellent. Developmental assessment shows 32% with delayed walking or sitting. However, 77% start school on time. Growth is only 9% below the third percentile for weight and 14% below the third percentile for height.1
OMPHALOCELE
Omphalocele is a congenital defect of the mid-line anterior abdominal wall, where the extruded abdominal organs are covered by a protective membrane (Fig. 396-2). The fascial defect and eviscerated organs are contained within the umbilicus. The defect can range in size from 2 to 15 cm. The incidence of omphaloceles is one in 7500 live births, a rate that has remained stable over the past few decades.2
PATHOGENESIS
Omphaloceles result from failure of fusion of the lateral embryonic folds at the umbilical ring. The viscera within the omphalocele can include any part of the GI tract, liver, spleen, bladder, and/or gonads and are covered with an opaque sac. This sac is composed of peritoneum, amnion and Wharton’s jelly. The umbilical cord inserts into the sac.
ETIOLOGY AND PATHOPHYSIOLOGY
Unlike gastroschisis, omphalocele is associated with additional abnormalities in up to 60% of infants.23 These associated anomalies may include structural defects of the heart, kidneys, limbs, and face. Omphaloceles have been associated with trisomy 13, 14, 15, 18, and 21 as well as other genetic syndromes. Beckwith-Weidemann syndrome (BWS), a defect in chromosome 11p15.5, consists of omphalocele, macrosomia, macroglossia, hypertrophy of solid organs, and a predisposition for developing childhood cancers.1,24 Since omphaloceles are often associated with several other anomalies, it is postulated that omphaloceles develop as a part of a field defects early in development. Alternatively, omphaloceles may result from a change in a basic cellular process that has far-reaching consequences, such as alternations in protein methylation seen in BWS. In one study, maternal consumption of multivitamins around the time of the gestation reduced the risk of isolated omphalocele by 60%.25
Unlike gastroschisis, infants born with omphaloceles are relatively protected from heat and fluid loss by the intact membrane covering the viscera. Small, covered omphaloceles usually do not have any physiologic consequences. Larger omphaloceles pose more physiologic and surgical challenges.
Giant omphaloceles are defined as defects greater than 5 cm in diameter that contain liver. In utero, the liver develops outside of the abdominal cavity, resulting in a globular liver and a limited abdominal domain. The omphalocele membrane is fragile and cannot support the underlying viscera. Giant omphaloceles are more likely to be associated with respiratory compromise due to pulmonary hypoplasia. In addition, the lack of muscular support in the epigastrium makes it difficult to have a coordinated diaphragmatic contraction. Some of these infants will require prolonged ventilatory support.
Unlike the gastroschisis patients, omphalocele patients do not have impaired gastrointestinal function when the sac remains intact. They have variable rotational anomalies. A Ladd procedure may be considered at the time of final closure.
PRENATAL DIAGNOSIS AND MANAGEMENT
Maternal serum α-fetoprotein is elevated in 90% of omphalocele cases. If an amniocentesis is performed, karyotype analysis should be performed. The amniotic fluid will not have elevated acetyl-cholinesterase levels, as is typically seen with gastroschisis. The accuracy of fetal ultrasound in detecting omphaloceles is 70% to 98%.1,2,16 Fetal MRI may be selectively considered in infants with omphaloceles. Cesarean sections are recommended in cases of giant omphalocele to prevent dystocia and omphalocele rupture. In these cases, a vaginal delivery may result in injury to the liver, which can be fatal.
FIGURE 396-2. Infant with omphalocele.
MANAGEMENT
The omphalocele sac must be carefully inspected for its integrity. Physical exam and radiologic studies of the infant should focus on identifying additional anomalies, in particular structural cardiac problems. This initial evaluation should include a chest X-ray, cardiac echocardiogram, and renal ultrasound. If the sac is intact, closure of the omphalocele is relatively elective. Priority then should focus on defining and initiating management of any cardiac anomalies.
Smaller defects are closed primarily. The sac is removed at the time of closure unless it is adherent to the liver. Closure of giant omphaloceles is not advised in the neonatal period. Giant omphaloceles are usually treated with topical agents to induce eschar formation and gradual epithelialization. Forcing the liver and other viscera into the abdominal cavity is impossible and may lead to abdominal compartment syndrome. Complete epithelialization can take weeks to months. Infants may require a stabilization device to support the liver and the viscera during this process. Occupational therapists create these devices in the newborn period.
Alternatively, giant omphaloceles may be managed by closing only skin over the viscera in the newborn period. Depending on the size of the defect and the infant’s comorbidities, staged fascial closure is performed in the first year of life. Prosthetic material may be required. If the sac is ruptured, a silo such as that used in a gastroschisis staged repair can be used.
OUTCOMES
Overall survival in children with abdominal wall defects with no other major congenital anomalies is excellent at greater than 90%.24,26 In a study of postoperative outcomes, neonates who were unable to be closed primarily had a prolonged length of stay and time to full enteral feeds.24 Omphalocele patients achieved primary closure in almost 60% of cases.1 Complications occur in 83% of patients, with the most common complication being wound infection (15%), sepsis (12%), and ileus (12%). Oral feeding is started without complication in 46% and delayed in 23% of patients. Reoperation during the initial hospitalization occurs in 31% of patients. Fifty-eight percent require readmission and 46% require further surgery.
Long term, only 10% of children report gastrointestinal disturbances with frequent difficulty. Seven percent report restriction with sports activities. Cosmetic results are good or excellent in most. Twenty percent report abdominal wall hernia, 27% have a developmental delay in sitting or walking, but 93% start school at the appropriate age. About 20% of patients have poor weight gain but height is normal in most.1
OTHER ABDOMINAL DEFECTS
Midline abdominal defects can occur during the seventh to eighth week of gestation. Defective fusion of the cranial fold is associated with failure of the septum transversum and fibrous pericardium to develop. These defects, if combined with thoracoabdominal ectopia cordis, intracardiac defects, omphalocele, cleft sternum, and diaphragmatic defects, define the Pentalogy of Cantrell. Lower midline abdominal wall defects can result in cloacal or bladder extrophy, imperforate anus, and neural tube defects.
These more complicated anomalies require a multispecialty and multidisciplinary approach, often requiring multiple operations for repair.