Newborn Abdominal Wall Defects

Historical Background

Omphalocele was first described by Ambrose Paré during the 16th century and was associated with poor prognosis; gastroschisis was likely described by Lycosthenes near the same time. The present-day diagnoses 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 and skin flap closure techniques. In 1899 Ahlfeld applied alcohol to the sac to induce eschar formation with subsequent contraction and epithelialization. Additional nonoperative management was later proposed by Ein and Shandling, who employed a skin-like polymer membrane to induce granulation of the sac surface. These techniques, however, resulted in a large, complex ventral hernia that required subsequent repair. Olshausen described the first surgical intervention for omphalocele in 1887 with skin flap coverage. Due to difficulty performing staged closure, Gross described a surgical procedure in 1948 in which he closed the skin over an intact omphalocele sac. These approaches also resulted in challenging ventral hernias.

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, applied sulfanilamide crystals, and closed with interrupted sutures. 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 applicable to both omphalocele and gastroschisis that revolutionized the management of neonatal abdominal wall defects. By attaching prosthetic material to the abdominal fascia at the 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 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 to the surgeon’s armamentarium provided an important tool for the management of neonatal abdominal wall defects; 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 course for these patients to allow for adequate nutrition during the slow recovery of bowel function inherent to neonatal abdominal wall defects.

Embryogenesis

Etiology

Proposed risk factors for abdominal wall defects may be demographic, genetic, pharmacologic, dietary, or lifestyle. Traditionally, gastroschisis has been associated with young maternal age and the presence of teratogenic factors. In contrast, omphalocele has been associated with young and advanced maternal age. 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. An inverse association between prepregnancy obesity and gastroschisis has also been demonstrated. Remaining risk factors involve exposure to vasoconstrictive substances including pseudoephedrine and phenylpropanolamine, smoking, cocaine, and methamphetamine.

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. In contrast to gastroschisis, maternal prepregnancy obesity is more frequent with omphalocele. 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 5000 live births, whereas gastroschisis is more common, with an incidence of approximately 1 in 2000 live births. While prevalence of omphalocele has remained stable in the United States, the prevalence of gastroschisis has increased, especially in mothers less than 20 years of age. Similarly, the birth incidence of gastroschisis increased in the United Kingdom and in Spain specifically for young mothers. ^, Increased prevalence was seen across ethnic and racial groups; however, the greatest increase was seen among non-Hispanic black mothers.

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. Omphaloceles are more likely to have a familial recurrence and have been reported in consecutive children, twins, and different generations of the same family. More recently, a familial association for gastroschisis has been demonstrated.

Anatomic Considerations

Omphalocele

The midline umbilical ring defect characterizing omphaloceles can range from small and easily treatable to very large (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 form a translucent, avascular membrane ( Fig. 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. There is no standard definition of giant omphalocele, although >5 cm is frequently used. Coexisting anomalies are more common among giant omphaloceles, and outcomes are worse.