Abdominal Wall Defects

Epidemiology

The prevalence of gastroschisis in the United States is 4.3 per 10,000 live births. However, in Europe it is reported to be lower at 2.0 per 10,000 births ranging from as low as 0.7 per 10,000 births in Italy to 5.5 per 10,000 births in England. There is no gender predilection in gastroschisis, but the incidence is higher in Hispanic and non-Hispanic white families. For unknown reasons, the incidence of gastroschisis has been reported to be increasing. In the United States, there was an increase in incidence from 4.49 per 10,000 live births in 2004 to 2006 to 5.12 per 10,000 live births in 2010 to 2014, and another recent national inpatient study also reported rising incidence from 4.5 to 4.9/10,000 live births from 2010 to 2014.

The most consistent risk factor for gastroschisis is young maternal age. Mothers under the age of 25 years have a several fold increased risk of carrying a baby with gastroschisis, and teen fathers have double the risk compared to fathers over 25 years. Numerous other maternal factors have been linked with gastroschisis, including short interpregnancy interval, prior pregnancy loss in mothers younger than age 20, illicit drug use (cocaine, amphetamines), alcohol consumption, prescription opioid use, low body mass index, cigarette smoking, anti-depressants, unmarried status, maternal nativity, and maternal genitourinary infections during gestation. Population-based studies also show a higher incidence of gastroschisis in areas where the common agricultural chemical atrazine is used and surface water concentrations of atrazine are elevated. However, a more recent study found no correlation of increased risk of gastroschisis in agricultural counties.

Pathophysiology

The embryology of gastroschisis is not completely understood. It occurs early in gestation and although there are rare family case reports, there is no known specific genetic etiology. Its association with young mothers is suggestive of a gene-environment interaction affecting fetuses with either a genetic predisposition or those exposed to unidentified exogenous factors. Pathologically, gastroschisis is a primary midline malformation involving the umbilical ring, with herniation of the intestines (without a covering sac) mostly to the right of the umbilical cord. Whether this represents a failure of closure of the primordial umbilical ring before the physiological hernia returns to the abdomen or a rupture of the covering membrane at the ring’s edge remains unclear. One theory is that gastroschisis occurs due to a ruptured physiologic hernia and the associated bowel injury is explained by a mesenteric insult.

Unlike omphalocele, extraintestinal anomalies are not common in gastroschisis, although congenital heart disease was reported in 4% of babies with gastroschisis. Anomalies of the intestine are the most common associated malformations in patients with gastroschisis. Nearly all babies with gastroschisis have intestinal malrotation since the bowel is not able to return to the abdominal cavity during fetal development and has no chance for normal rotation and fixation to the retroperitoneum. Intestinal atresia occurs in 10% to 25% of babies with gastroschisis.

Clinical Presentation

With routine prenatal ultrasound, about 90% of gastroschisis cases are diagnosed early in pregnancy. Prenatal ultrasound shows extra-abdominal loops of bowel without a covering sac. The maternal alpha fetoprotein level is also elevated. Currently there are no options for fetal intervention, but amnio exchange and fetal repair are being studied as possible future options.

Fetuses with gastroschisis have a significant risk of intrauterine growth restriction (IUGR), spontaneous preterm labor, and intrauterine fetal death (IUFD). IUGR is a frequent indication for preterm delivery in fetal gastroschisis; however, ultrasound has a low accuracy for diagnosing small for gestational age (SGA) status at birth and the standard formula (that uses the abdominal circumference to calculate fetal growth) has been reported to underestimate the fetal weight. The incidence of IUFD with fetal gastroschisis is approximately 4.5% to 5.2%, which is higher than the reported 2.8% in uncomplicated pregnancies. The mechanisms for sudden fetal death are unclear and possibly related to oligohydramnios, cord compression, vascular compromise, or volvulus. Genetic testing of the fetus with gastroschisis is not routinely performed due to lack of specific genetic etiology.

Management

Babies with gastroschisis are best cared for by a multidisciplinary team of maternal fetal medicine specialists, neonatologists, and pediatric surgeons. Prenatal consultation with this group is strongly recommended. Rigorous prenatal surveillance with ultrasounds every 1 to 3 weeks is recommended starting at 24 weeks to evaluate the bowel anatomy, fetal growth, and amniotic fluid volume. Twice weekly nonstress testing (NST) is recommended starting at 32 weeks.

The timing of delivery in gastroschisis remains controversial. Planned preterm delivery is believed by some to reduce IUFD and postnatal complications, but there are no high-quality data to validate this approach, and retrospective studies have conflicting results. Two randomized controlled trials failed to show any benefit of elective preterm delivery; however, a systematic review reported benefits with decreased neonatal sepsis. A study evaluating the risk of IUFD and neonatal death concluded that mortality can be minimized with delivery at 37 weeks, while another study reported delivery at 38 weeks was associated with decreased risk of stillbirth and a minimal increase in neonatal respiratory morbidity. A literature review concluded that elective delivery at less than 37 weeks is generally not indicated, and delivery should be scheduled between 37 and 38 weeks for uncomplicated gastroschisis. The argument against planned preterm delivery is bolstered by contemporary outcome studies that consistently demonstrate that preterm delivery is a major source of adverse neonatal outcomes in gastroschisis, and IUFD did not increase after 35 weeks. Neonates with gastroschisis delivered at less than 37 weeks had longer hospital stays; however, there were no differences in neonatal outcomes between planned delivery at 36 to 37 weeks or at ≥38 weeks. Many centers now advocate for delivery close to term.

There is a stronger consensus regarding vaginal delivery for patients with gastroschisis. Cesarean section seems to offer no benefit to the baby or the mother and increases the risk of neonatal respiratory distress. A recent metaanalysis found no difference with elective cesarean section in neonatal mortality or morbidity such as sepsis, short gut syndrome, and duration of hospital stay. Cesarean section is thus not recommended solely for gastroschisis and the delivery mode should be on standard obstetrical indications.

At birth, the umbilical cord should be kept long and clamped at least 30 cm from the baby to preserve the option of primary umbilical closure. Neonatal resuscitation should follow standard protocols, except for placing the baby’s lower body, from the nipples to the feet, in a clear plastic bag as a temporary covering over the exposed bowel to minimize evaporative heat and fluid loss. After initial newborn resuscitation measures are performed, the perfusion of the herniated intestinal contents should be carefully evaluated. If bowel ischemia or infarction are suspected, bowel detorsion or emergency enlargement of the gastroschisis defect by a surgeon may need to be performed. An oro- or nasogastric tube is placed to suction to empty the stomach. The baby should be kept warm and dry.

After initial resuscitation and stabilization, the patient is urgently transported to a NICU with pediatric surgical consultation. In the NICU, a peripheral intravenous line is inserted to start intravenous fluids and broad-spectrum antibiotics. Endotracheal intubation is not required unless indicated for respiratory support. Noninvasive positive pressure ventilation is generally avoided to prevent distension of the eviscerated bowel. The baby should be placed with the right side angled slightly down to prevent kinking of the mesentery and maximize blood flow to the bowel. The oro- or nasogastric tube should remain on suction. Bowel perfusion should be visually monitored through the clear plastic bag; opening the bowel bag should be avoided until surgical assessment to avoid further contamination of the bowel.

The goal of surgical repair in gastroschisis is safe reduction of the eviscerated contents and closure of the abdominal wall. Multiple surgical options exist to accomplish this goal, and both primary repair and staged repair are acceptable options.

Sutureless abdominal wall closure in gastroschisis uses the patient’s own umbilical cord as a biologic dressing to seal the gastroschisis defect without attempting a primary fascial closure. The cord is left long at delivery, and the eviscerated contents are reduced into the abdominal cavity while monitoring intra-abdominal pressure. The fascial defect is covered with the coiled umbilical cord that is secured into place with a bandage ( Fig. 62.4 ). In most cases, the gastroschisis defect contracts and the skin heals beneath and around the cord within 14 days. Using sutureless closure, some children will have a persistent umbilical hernia that can be repaired electively at 3 to 4 years of age.

Sutured abdominal wall closure of gastroschisis is now less commonly performed. Sutured closure involves closing the fascial defect with sutures in the operating room under general anesthesia. Intra-gastric or bladder pressure is monitored to ensure the closure does not cause abdominal compartment syndrome. In some cases, a prosthetic patch is required to close the defect. An umbilicoplasty is then performed.

Staged repairs with initial silo coverage of gastroschisis are an accepted surgical strategy that entails delayed reduction of the herniated bowel and closure of the abdominal wall. Silos may be created from silastic or other plastic sheeting and sewn circumferentially to the fascial edges of the gastroschisis defect ( Fig. 62.5 ). Another option is to use a pre-made, spring-loaded silastic silo that is manufactured in different diameters and can be inserted into the gastroschisis defect at the bedside ( Fig. 62.6 ). Once a silo is placed, the bowel gradually reduces over several days into the abdominal cavity by either gravity alone or gentle external pressure. When the reduction takes more than 7 to 10 days, the risk of silo dehiscence from the abdominal wall increases. Delayed sutured abdominal wall closure is performed when the abdominal contents have almost completely reduced into the abdominal cavity. There is also the option of using the sutureless umbilical cord closure technique in a delayed fashion after the bowel has reduced in the silo if the cord is kept moist with dressings. The delayed approach requires close monitoring of the bowel appearance through the silo.

Despite many retrospective studies, database analyses, and meta-analyses, it is unclear which surgical approach is best for any individual baby with gastroschisis. Many studies suffer from significant selection bias and do not separately analyze patients with complex gastroschisis, thereby making outcome comparisons difficult. Two randomized, prospective studies to evaluate primary versus delayed fascial closure have not found significant outcome differences between techniques. A meta-analysis suggests that delayed primary repair may be associated with improved outcome measures when studies with selection bias are eliminated from the analysis.

The choice of primary fascial closure versus delayed repair using a silo may be less relevant in the era of sutureless abdominal wall closure. Primary sutureless umbilical cord closure is successful in many babies with gastroschisis, may be performed at the bedside, does not always require general anesthesia, and reduces duration of mechanical ventilation. In our experience, sutureless umbilical closure is associated with shorter NICU stays and shorter time to initiation of enteral nutrition, as well as decreased hospital costs, ventilator days, and time to goal enteral feeding compared to delayed closure with a silo. One retrospective case control study showed a decrease in mechanical ventilation of 2.8 days and reduction in need for general anesthesia in patients with sutureless versus sutured repair. A multicenter cohort study by the Midwest Pediatric Surgery Consortium reported that sutureless closure was associated with less general anesthetics, antibiotic use, surgical site infections, and decreased ventilator time. In contrast, a single-institution randomized controlled trial comparing sutureless versus sutured primary closure in simple gastroschisis found increased time to full feeds and discharge among patients with primary sutureless closure. Multicenter randomized clinical trials are needed to determine the potential advantages of the sutureless approach.

The gastroschisis prognosis score (GPS) is a validated bedside visual bowel-injury-scoring tool performed after birth. It is helpful for distinguishing low from high morbidity groups and assists in initial counselling. Babies with uncomplicated gastroschisis have average hospital stays of 4 to 6 weeks, which is largely due to their inability to tolerate full enteral feedings. Babies with complicated gastroschisis often have much longer hospital stays.

Outcomes

Outcomes for children born with gastroschisis in high-income countries are excellent. Survival of greater than 95% can be expected in cases of uncomplicated gastroschisis. Infants with complex gastroschisis are at higher risk for overall mortality (2%), need for assisted ventilation (95%), bowel resection (10%), necrotizing enterocolitis (5%), sepsis (9%) and need for home parenteral nutrition after discharge (2%). While only a small minority of babies with gastroschisis will need extensive bowel resection, gastroschisis remains a leading etiology of short bowel syndrome in most series of children with intestinal failure. In resource-limited settings, mortality remains very high, primarily due to lack of access to total parenteral nutrition, which is required when awaiting return of bowel function. Targeted interventions such as improving prenatal diagnosis and management protocols for earlier enteral feeding, adequate vascular access, and fluid resuscitation have demonstrated improved outcomes in resource-limited settings.

Long-term outcomes in gastroschisis are favorable. Most patients will have normal gastrointestinal function and neurodevelopmental outcomes. Even though gastroschisis is almost always associated with intestinal malrotation, the risk of midgut volvulus later in life is low (reported at 1%), probably because intra-abdominal adhesions limit the ability of the bowel to twist. These patients may develop hernias at the site of repair. Finally, although boys with gastroschisis commonly have undescended testicles, about 50% of patients will undergo spontaneous testicular descent and not require an operation.

Epidemiology

The incidence of omphalocele is estimated to be 1.5 to 3 per 10,000 births. The incidence of omphalocele has been stable over time, unlike the incidence of gastroschisis, which is increasing. Most cases of omphalocele are sporadic and often associated with chromosomal anomalies, but there are rare familial occurrences.

Risk factors for omphalocele include a maternal age less than 20 years or greater than 40 years, and maternal obesity. In contrast to the relatively low risk of associated anomalies in babies with gastroschisis, babies with omphalocele are twice as likely as those with gastroschisis to present with other birth defects. These associated anomalies play a major role in how patients are managed and in their eventual outcome. Chromosomal anomalies such as trisomy 13 and 18 are common, especially in fetuses diagnosed early in gestation. In addition, other congenital malformations are frequent, especially congenital heart disease, which may occur in up to 50% of newborns with omphalocele. Finally, omphalocele is a component of several syndromes of congenital malformations, including Beckwith-Wiedemann syndrome, which occurs in 6% of newborns with an omphalocele. Up to 10% to 20% of newborns thought to have an isolated omphalocele have Beckwith-Wiedemann syndrome on prenatal evaluation.