Pediatric Omphalocele and Gastroschisis (Abdominal Wall Defects)

Ventral abdominal body wall defects comprise a group of congenital malformations that includes gastroschisis and omphalocele, which are relatively common, and ectopia cordis, bladder exstrophy, and cloacal exstrophy, which are extremely rare. Gastroschisis is the congenital anomaly most frequently encountered by pediatric surgeons, and the incidence is rising. The incidence of omphaloceles, however, has remained relatively constant.[1]

The reported incidence of abdominal wall defects in the United States is estimated to be the following:

• Gastroschisis: 1 case in 2,229 births (about 1,871 infants each year)[2]

• Omphalocele: 1 case in 5,386 births (about 775 babies annually)[2]

• Bladder exstrophy: 1 case in 50,000 births[3]

• Ectopia cordis: 1 case in 125,000 births[4]

• Cloacal exstrophy: 1 case in 10,000 - 70,000 to 1 case in 200,000 - 400,000 births[5]

There is also anatomic variation regarding the size and location of the abdominal wall defect, as well as a spectrum of associated anomalies:

• Gastroschisis: Small paraumbilical defect, associated intestinal abnormalities
• Omphalocele: Central umbilical defect of varying size; omphaloceles may be syndromic (genetic) or have associated system abnormalities
• Epigastric omphalocele (pentalogy): Associated diaphragmatic, sternal, pericardial, and heart abnormalities
• Bladder exstrophy: Lower abdominal wall and pelvis, associated genitourinary abnormalities
• Cloacal exstrophy: Bladder exstrophy plus an imperforate anus

Furthermore, within each category, there is a spectrum of severity with regard to the initial problem and the anticipated secondary problems.

An infant with gastroschisis may have intestinal dysfunction. Prolonged exposure to amniotic fluid may cause mucosal or muscularis injury, although the etiology of bowel injury in gastroschisis is unclear. If noxious elements in the amniotic fluid were responsible, amnioexchange should be therapeutic. Unfortunately, the anticipated benefit has not occurred.[6] Or, potentially or a small abdominal wall defect may constrict the mesentery, causing ischemic injury or actual necrosis.

Intestinal obstruction, from inflammatory adhesions or from Ladd bands, a component of malrotation, may complicate the infant's recovery. Malrotation occurs in the setting of developmental anomalies, in which the intestine fails to return to the nascent abdominal cavity, such as congenital diaphragmatic hernia as well as abdominal wall defects. Midgut volvulus, the most feared complication of malrotation, is theoretically possible but unlikely because of postsurgical adhesions. The appendix is abnormally located in the upper abdomen in patients with malrotation; however, the availability of computed tomography (CT) scanning to evaluate the abdomen makes this less of an issue. Children with gastroschisis may suffer from gastroesophageal reflux; the prevalence of Hirschsprung disease is also increased.

See the Medscape Drugs & Diseases articles Omphalocele Imaging and Gastroschisis Imaging, as well as information from the Children's Hospital of Philadelphia on Omphalocele and Gastroschisis.

See also the Critical Images slideshow 11 Abdominal Emergencies in Infants.

Embryology

Following fertilization, cellular division generates a hollow sphere, bisected by a bilaminar plate composed of epiblast and hypoblast, which abut the amnion and yolk sac cavities respectively.[7] The epiblast cells form the embryo; the hypoblast develops into the placenta. The bilaminar disc is divided axially by the primitive streak, at the apex of which is the primitive node. Epiblast cells pour into the primitive node, converting the bilaminar disc into a disk with three germ cell layers. Invagination occurs along the primitive streak, giving the embryo (in cross-section) the appearance of an omega. The curved portion of the omega fuses, forming the neural tube (central nervous system [CNS]) and displacing the notochord ventrally. The pinched-off tissue, dorsal to the neural tube, becomes epiderm. Laterally, the mesoderm undergoes differentiation: para-axial (peripheral nervous system), intermediate (gonads and kidneys), and lateral, which further divides into splanchnic (gastrointestinal [GI] tract) and somatic (body wall). The splanchnic mesoderm and endoderm fuse ventrally to form a tube (the GI tract); the somatic mesoderm and epiderm layers fuse anteriorly forming the anterior body wall and abdominal cavity (intraembryonic coelom). The embryo is surrounded by amnion, which encloses the extra-embryonic coelom.[8]

During the sixth week of development, rapid growth of the liver and intestines causes herniation of the midgut into the amniotic cavity. By the 10th week, the abdominal cavity is sufficiently large to accommodate return of the midgut. Rotation and fixation of the proximal and distal midgut (duodenum and ascending colon) occurs upon their return.

As the hindgut elongates, ingrowth of mesoderm forms the urorectal septum. Mesoderm also invades the cloacal membrane, uniting the genital tubercles and creating the urogenital sinus.

The body folds unite where the amnion invests the yolk sac and body stalk. Fusion is a complex process: A surface glycoprotein promotes adhesion between opposing segments of the nascent body wall; migration and apoptosis (planned cellular death) knit together the cephalic, caudal, and lateral folds about the attenuated yolk sac, causing constriction of the umbilical ring.

Omphaloceles and gastroschisis

Omphaloceles

In infants with omphaloceles, the intestines do not return to the abdominal cavity; rather, they remain within the extra-embryonic coelom (amniotic cavity) bounded by the umbilical ring.[9] (See the image below.)

There is evidence to suggest that omphaloceles have a genetic etiology, as follows:

• Omphaloceles are associated with increased maternal age.

• Omphaloceles occur in twins, consecutive children, and different generations of the same family.

• Omphaloceles are associated with trisomy 13, 18, and 21 (in 25%-50 % of cases) and with Beckwith-Wiedemann syndrome

Gastroschisis

In gastroschisis, there appears to be a weakness in the body wall (caused by defective ingrowth of mesoderm, or impaired midline fusion, or inappropriate apoptosis) that allows the intestines to herniate through this defect into the amniotic cavity. (See the following image.)

Gastroschisis occurs in young mothers with low gravida; it is associated with prematurity and small-for-gestational-age (SGA) infants, and denotes in utero growth retardation.

The clustering of cases (number and severity) suggests a multifactorial etiology, including environmental factors acting upon susceptible hosts.

Other abdominal wall defects

Issues to consider in understanding the spectrum of body wall defects include the following:

• Is a sac is present?

• Is it ruptured?

• Are there associated anomalies? (This suggests omphalocele, as they are twice as more prevalent in omphalocele than gastroschisis.[10] )

Associated anomalies include:

• Congenital heart disease

• Cleft palate

• Musculoskeletal abnormalities

• Dental malocclusion

• Intestinal atresia

• Patent omphalomesenteric duct remnant (looks like a stoma at the base of the umbilical cord)

Hernias of the umbilical cord

In hernias of the umbilical cord, the umbilical ring is oversized, but the relationships of amnion to yolk sac and connecting stalk are normal. (See the image below.)

Urachal remnants and omphalomesenteric duct malformations

Urachal remnants[11] and omphalomesenteric duct malformations[12] are the result of insufficient apoptotic cell death in the urachus and yolk stalk. (See the following images.)

Bladder exstrophy

The bladder develops between the fifth and ninth gestational weeks (postfertilization).[13] By 10 weeks, urine is produced and mixes with the amniotic fluid; this is crucial for normal lung development.

In healthy infants, the bladder is visible on ultrasonography toward the end of the first trimester. In these patients, the bladder is open with exposed mucosa, forming a protruding disc below the umbilical cord, which is displaced caudally. The pelvic rami are spread apart; consequently, the pelvis is shallow and lacks depth. Hence, the developing bladder, urethra, vagina, and rectum are displaced anteriorly. The abnormal position of these organs interferes with normal development of the lower abdominal wall. (See the images below.)

Prune-belly syndrome

Prune-belly syndrome includes dilatation of the ureter, collecting system, and bladder; undescended testes; and other abnormalities. This syndrome is caused by increased "apoptotic" cell death in the body-wall placode or inadequate migration of mesodermal cells, with retention of yolk sac elements.[13]

Characteristics of prune-belly syndrome include the following:

• There is attenuation of the abdominal musculature.

• Muscle fibers are absent and are replaced by thick collagenous aponeuroses.

• Paradoxically, hypoplasia of the abdominal wall contrasts with hypertrophy of the bladder wall, which may cause bladder neck obstruction and the characteristic megaureters and dilated renal collecting system.

• Faulty intercellular electrical conduction causes disordered muscular contraction and ineffective ureteric peristalsis.

• Approximately 95% of infants with prune-belly syndrome are male; the absence of prostatic and seminal fluid precludes normal sperm development and causes infertility, as may the associated cryptorchidism.

Cloacal exstrophy

The urorectal septum divides the cloaca into the urogenital sinus and the rectum. Defective enfolding of the embryo's caudal pole, and deficient incorporation of the yolk sac and allantois into the urogenital sinus, leads to malformation of the external genitalia.

The cloaca persists in the absence of mesodermal ingrowth. Differentiation of the genitourinary system and hindgut are arrested, and development of the lower abdominal wall is thwarted.

Cloacal exstrophy is associated with mutations in the homeobox genes. (See the following images.)

In rat studies, folic acid deficiency, hypoxia, and salicylates cause abdominal wall defects to develop, but the clinical significance of these experiments is conjectural.

Elevation of maternal serum alpha-fetoprotein (MSAFP) is associated with omphalocele and gastroschisis. An elevated MSAFP warrants ultrasonographic evaluation to determine if structural abnormalities are present in the fetus. If the study is suspicious for an omphalocele, amniocentesis is indicated to determine the presence of an associated genetic abnormality.

Polyhydramnios occurs in association with intestinal atresia, which may complicate gastroschisis. If polyhydramnios is identified by fetal ultrasonography, the mother should be referred to a tertiary care facility for optimal care of her newborn. Generally, newborns requiring surgery are best managed at tertiary care centers.

United States data

Analysis of 2012-2016 data from 30 US population-based birth defect surveillance programs by the National Birth Defects Prevention Network (NBDPN) focused on abdominal wall defects, specifically gastroschisis and omphalocele. It found an overall prevalence of 4.3 per 10,000 live births for gastroschisis and 2.1 per 10,000 live births for omphalocele.[10] Gastroschisis was more frequent among mothers younger than 25 years and more likely to occur when mothers had low or normal prepregnancy weights; it was half as likely as omphalocele to occur in conjunction with other birth defects. Omphalocele was more common in mothers older than 40 years, more likely to occur in overweight/obese mothers, and twice as likely as gastroschisis to concomitantly occur with other birth defects.[10]

Allman et al evaluated retrospective discharge data (1997-2015) for the prevalence of infants with gastroschisis in US neonatal intensive care units (NICUs). Of 1,158,755 total discharges, 6,023 infants (5.2 per 1000 discharges) had gastroschisis and 1,885 (1.6 per 1000 discharges) had an omphalocele.[14] The rate of gastroschisis increased from 2.9 to 6.4 per 1000 discharges over a 12-year period (1997-2008), gradually declined over the next 4 years (2008-2011) from 6.4 to 4.7 per 1000 discharges, and then remained stable thereafter. The rate of omphalocele was stable over the same time periods, at 1-2 per 1000 discharges.[14]

International data

The combined incidence of omphalocele and gastroschisis is 1 case per 3,500 births. Epidemiologic data compiled over the last four to five decades show that the incidence of omphalocele has remained constant, whereas that of gastroschisis has increased three- to four-fold. See the table below.

Table 1. Incidence Rates for Gastroschisis and/or Omphaloceles in Various Regions and Time Periods. ^{[1, 15, 16, 17]} (Open Table in a new window)

Race- and sex-related demographics

Neither gastroschisis nor omphalocele has a geographic or racial predilection. The Texas data indicate that gastroschisis occurs in diminishing frequency among Latinos, white persons, and black persons.[1]

The male-to-female ratio is about 1.5:1.

Omphalocele

Care of infants with omphaloceles may be simple or complex, depending upon the size of the defect, and the presence and severity of associated problems.

Infants with giant omphaloceles, in which the liver is centrally located and contained within the omphalocele sac, usually have small, bell-shaped thoraces and pulmonary hypoplasia. These babies frequently require tracheostomies and assisted ventilation. Even so, patience and optimism should be encouraged, as growth of the thoracic cavity and maturation of the lung may eventuate in a gratifying outcome.

Gastroschisis

The prognosis of infants with gastroschisis depends upon the severity of associated problems, such as prematurity, intestinal atresia and dysfunction, and possibly short gut. A population-based cohort study from 28 pediatric surgical centers in the United Kingdom and Ireland analyzed the 1-year outcomes of infants with gastroschisis and found that infants with complex gastroschisis required longer hospital stays and had more complications than infants with simple gastroschisis.[18] Classifying infants with gastroschisis into "simple" versus "complex" (macroscopic intestinal abnormalities) may be a reliable predictor of outcome.[18] A separate population-based study of 502 Australian infants with abdominal wall defects (166 omphalocele, 336 gastroschisis) reported similar findings of longer hospital stays and parenteral nutrition as well as higher rates of infection but lower overall mortality in infants with gastroschisis compared to those with omphalocele.[19]

The prognosis has been greatly improved by antenatal sonography, which allows identification of infants with abdominal wall defects and referral to tertiary centers where prenatal, obstetrical, and pediatric surgical expertise is available.[15, 16, 20]

Morbidity/mortality

The mortality of omphaloceles relative to gastroschisis is 8:1. Irreversible pulmonary hypertension and right heart failure is the usual terminal event.

In a 2018 literature review of 23 articles comprising 396 giant omphaloceles, the outcome was lethal in in nearly 23% (n = 90) of neonates, with sepsis the primary cause in more than half of these patients (56.6%; n = 51).[21] Two predictors of mortality were pulmonary hypoplasia and respiratory failure; prematurity and ruptured sacs were also implicated.[21]

Factors adversely influencing the management of infants with gastroschisis are as follows:

• Prematurity and low birth weight

• Hypothermia (exposure of the intestine to the ambient environment)

• Dehydration (gastrointestinal losses, in addition to the above factors)

• Sepsis (open wound)

• Hypoglycemia (stress with little metabolic reserve)

• In utero growth restriction (protein loss from the extruded intestines)

• Oligohydramnios

• Fetal distress and birth asphyxia

• Injury to the intestines during delivery (tearing or cutting the bowel or mesentery) or transport (allowing the eviscerated intestines to fall alongside the infant, stretching or torquing the mesenteric vessels)[22]

Improvements in respiratory care, pharmacology (antibiotics and total parenteral nutrition), anesthesia, transport, and surgery have increased the survival rates for these infants from 60% during the 1960s to more than 90% in more recent years.[15, 16, 20]

See the images below.

Long-term morbidity from gastroschisis is related to intestinal dysmotility (pseudointestinal obstruction), malabsorption (mucosal injury), short gut, and gastroesophageal reflux disease. Difficulty obtaining wound closure contributes to morbidity by prolonging intestinal dysfunction (ileus) and creating ventral hernias, which may require surgical repair.[23, 24, 6, 25]

The following scenarios may cause short-gut syndrome, in which the intestinal length is inadequate:

• An antenatal mesenteric vascular accident may cause intestinal atresia.

• Constriction of the extruded intestine's mesentery by a small abdominal wall defect may cause in utero gut infarction ("closing gastroschisis").

• Tethering the eviscerated bowel's mesentery impairs blood flow and may cause vascular injury.[22]

• Excessive tension from closure of the abdominal wall defect results in the "abdominal compartment syndrome," in which the intra-abdominal pressure exceeds the splanchnic perfusion pressure and nutritive blood flow ceases.

Closed-loop obstructions, in which both efferent and afferent limbs of the intestine are blocked, occur in volvulus (twisting of the entire midgut and its mesentery), or a single loop of intestine may flip around a point of fixation, such as an adhesion to the abdominal wall. This causes unrelieved distention and ischemic injury of the intestines (ie, "strangulation obstruction").[26]

The injury produced by antenatal exposure of the intestine to amniotic fluid (mucosal and muscular) leads to diminished absorption and impaired peristalsis, which compounds the crippling effect of the diminished length of short-gut syndrome.

The care of infants with short-gut syndrome has improved with innovations in parenteral and enteral nutrition, venous access devices, prevention and early treatment of catheter sepsis, innovative surgical procedures to optimize gut length, and aggressive treatment of bacterial overgrowth in stagnant loops of intestine. Infants with short-gut syndrome from gastroschisis account for a substantial number of children who undergo intestinal transplantation.[27, 28]

See the images below.

Infants with giant omphaloceles usually have small, bell-shaped thoraces and minimal pulmonary reserve. Repair of the omphalocele may precipitate respiratory failure by limiting diaphragmatic excursion.

Occasionally, infants are encountered with anomalies whose adverse effects are additive, such as a giant omphalocele plus a diaphragmatic hernia. Pulmonary hypoplasia occurs in both conditions; when they occur together, their effects are so severe as to preclude survival, despite extracorporeal membrane oxygenation (ECMO) support.

Even with successful repair of a giant omphalocele, the liver remains located in the midepigastrium, where it lacks the normal protection afforded by the lower rib cage and where it is more vulnerable to injury. See the following image.

A study by Corey et al indicated that compared with infants with gastroschisis, those with omphalocele have a higher incidence of other anomalies, are more likely to have pulmonary hypertension, and have a higher mortality rate.[29] In the study, which involved 4,687 infants with gastroschisis and 1,448 with omphalocele, the investigators found that 35% of the patients with omphalocele had at least one other anomaly, as compared with 8% of those with gastroschisis. The odds ratios for pulmonary hypertension and mortality in infants with omphalocele compared with those with gastroschisis were 7.78 and 6.81, respectively.[29]

Complications

Babies whose omphaloceles are treated conservatively ("paint and wait") have increased caloric requirements, because of their large open wound. Positive nitrogen balance is restored following skin closure.

Prolonged parenteral nutrition can cause hepatotoxicity, manifested by cholestasis and hepatomegaly, which may complicate a staged closure of a giant omphalocele. Omega-3 fatty acids (Omegaven) reportedly may reverse "intestinal failure associated liver disease."

Infants with giant omphaloceles have pulmonary hypoplasia in addition to diminutive thoraces; they may require tracheotomies and ventilatory support. Abdominal wall closure transiently increases intra-abdominal pressure; paradoxically, reconstituting the infant's torso improves muscular function and may enable ventilator weaning.

Infants with giant omphaloceles have an increased risk of sepsis,[21] because of the open wound and need for ventilatory support and central venous access.

Instruct parents of infants with gastroschisis or omphalocele regarding the significance (ominous) of bilious emesis, because this may indicate that adhesive small-bowel obstruction or midgut volvulus has occurred.

Also inform parents that their child's appendix is located in an unusual location and that computed tomography scanning is the most reliable way to diagnose acute appendicitis.

Infants with gastroschisis and omphalocele can be identified by prenatal ultrasonography.[30] Defects in other organ systems may also be diagnosed, and chromosomal abnormalities may be discovered by amniocentesis. See Workup.

Omphalocele

In an omphalocele, the diameter of the abdominal wall defect varies between 4 and 12 cm; the defect is located centrally, or in the epigastrium or the hypogastrium.

With a large omphalocele, dystocia may occur and cause liver injury.

The omphalocele sac is ruptured in 10%-20% of cases; rupture may occur in utero or during delivery.

Infants with Beckwith-Wiedemann syndrome have the following characteristics:

• Omphalocele (generally small)

• Macroglossia and coarse, rounded facial features

• Visceromegaly with hyperplasia of the pancreatic islet cells causing neonatal hypoglycemia, which may be severe

• Genitourinary abnormalities

Increased incidence of Wilms tumors, liver tumors (hepatoblastoma), and adrenocortical neoplasms; surveillance by ultrasonography is indicated

Pentalogy of Cantrell includes the following components[31] :

• Epigastric omphalocele

• Cleft sternum

• Anterior (retrosternal) diaphragmatic hernia of Morgagni

• Absent pericardium

• Cardiac defects (ectopia cordis and ventricular septal defects)

  Pediatric omphalocele and gastroschisis (abdominal wall defects). This infant has pentalogy of Cantrell: an epigastric omphalocele, cleft sternum, anterior (retrosternal) diaphragmatic hernia of Morgagni, absent pericardium, and cardiac defects (ectopia cordis, ventricular septal defects).

Giant omphalocele features are as follows:

• Large, centrally located, abdominal wall defect

• Ectopic liver, located outside of the abdominal cavity, within the omphalocele sac

• Small, undeveloped abdominal and thoracic cavities

• Restrictive lung disease and pulmonary hypoplasia associated with the hypoplastic thoracic cavity

• Best to accomplish operative closure in stages (to avoid excessive intra-abdominal pressure)[32]

Gastroschisis

The abdominal wall defect of gastroschisis is generally uniform in size (≤5 cm) and constant in location (right of the umbilical cord).

The amount of inflammation of the extruded intestine varies. Inflammation may be minimal, or it may distort the appearance of the bowel, obscuring the anatomy and making it difficult even to identify an atresia. See the images below.

The amount of inflammation, the distribution of meconium (whether it can be evacuated manually through the anus), or whether succus entericus can be milked into the stomach and suctioned (by anesthesia), are factors that determine whether reduction and closure of the abdominal wall defect can be accomplished primarily or whether a "silo" must be used.

When primary closure of the abdominal wall defect is not possible, a silo is utilized to contain the intestine until the inflammation has resolved and it becomes soft and pliable. Usually, reduction be accomplished within 1 week. Correction of intestinal atresia, by either an anastomosis or an enterostomy, is best delayed until closure of the abdominal cavity has been achieved.

Intestinal dysfunction, delaying the onset of feedings, may take 4-6 weeks to resolve.

When gastroschisis is identified antenatally, serial ultrasonography is performed to identify compromise to the intestinal viability.

Concomitantly, amniocentesis monitors lung maturity and signals when to induce labor.[33, 34, 35, 36, 37]

Cloacal exstrophy

Characteristics of cloacal exstrophy include the following:

• Bladder exstrophy with a central strip (plate of cecum) and prolapsed ileum (elephant trunk appearance)

• Potential presence of duplication of the colon and appendix, or colonic atresia, or imperforate anus

• Myelodysplasia (tethered cord, myelomeningocele, hydromyelia, diastematomyelia)

• Fetal uropathy with oligohydramnios and pulmonary hypoplasia

• Compression abnormalities: Indented thorax, malformed digits, talipes (club foot), bowed limbs, and dislocated hips

• Low-set ears

See the following images.

Laboratory studies

Elevation of maternal serum alpha-fetoprotein (MSAFP) is associated with abdominal wall defects. MSAFP levels are higher in gastroschisis than in omphalocele, and they are also increased in spina bifida, which additionally increases the ratio of acetylcholinesterase and pseudocholinesterase.[6]

Imaging studies

In utero ultrasonography may demonstrate a structural defect that is associated with a karyotypic abnormality.[38] If a genetic abnormality is suspected in the infant, it should be confirmed with amniocentesis.

Fetal echocardiography may identify a cardiac abnormality.

If serial ultrasonography shows dilatation and thickening of the intestine in a baby with gastroschisis, delivery should occur as soon as amniocentesis demonstrates lung maturity.

Appropriate tests to determine other congenital anomalies should precede surgical intervention in infants with omphaloceles.

See the Medscape Drugs and Diseases topics Gastroschisis Imaging and Omphalocele Imaging.

Transfer

When transferring infants with ventral abdominal body wall defects, covering the intestines with warm, moist lap pads seems reasonable, but the heat is soon dissipated. A better approach is to:

• Cover the intestines with a nonadherent, semi-permeable membrane (eg, plastic cling wrap such as Saran Wrap). Then,
• Wrap dry Kerlex dressing around the intestines, including the infant's torso, so that the intestines are situated just above the abdominal wall defect. Then,
• Place the infant in a bowel bag.

This technique minimizes the loss of heat and moisture from the exposed intestines, as well as protects the mesentery from twisting or stretching.[22] A radiant warmer should only be used if the intestines are protected.

Intravenous fluids are administered to counter evaporative and third space (GI tract) losses; an orogastric tube is placed to prevent gastric distention from swallowed air. Antibiotics are indicated, in view of the open peritoneal cavity and exposed bowel.

Drug therapy

Drug therapy is determined by the exigencies of caring for an ill premature baby.

Omphalocele

Intestines within an intact omphalocele are protected from the amniotic fluid; hence, these babies tolerate feedings promptly after the abdominal wall defect is closed. Infants with giant omphaloceles, however, usually require prolonged hospitalization. Because their respiratory reserve is limited, reduction and closure in these babies should be accomplished gradually. "Paint and wait" is perhaps the safest approach: Topical antimicrobials are applied to the omphalocele membrane, and the infant's torso is wrapped with an elastic bandage (eg, ACE bandage). Healing occurs by epithelialization and wound contracture. These babies may require ventilatory assistance and tracheostomies.

Gastroschisis

If the appearance of the intestines is normal in an infant with gastroschisis, reduction and closure are usually feasible. A relatively recently proposed technique is "sutureless closure," in which, following reduction of the eviscerated bowel, the umbilical cord is used to fill the opening in the abdominal wall and then is secured in place with an adhesive dressing.

If the intestines are inflamed and abdominal wall closure is not possible, the intestines are placed within a silo and reduction is accomplished over the subsequent 7-10 days.

Parenteral nutrition allows for continued growth and healing; intestinal recovery is signaled by the passage of "starvation stools." If intestinal function is delayed beyond 4-6 weeks, a contrast bowel study should be obtained to assess transit of contrast medium through the intestines. If this study demonstrates a mechanical obstruction, laparotomy is indicated.

Intestinal inflammation

Intestinal inflammation may occur in the setting of gastroschisis or ruptured omphaloceles.

The intestines may be pristine, as in a fresh laparotomy, or they may be stiff and edematous, matted together, and covered by an inflammatory “peel.” Appearance predicts function: In the first setting, infants tolerate feedings promptly, whereas injury from amniotic fluid exposure or ischemia is associated with intestinal dysmotility and malabsorption. Histologic evaluation shows atrophy of myenteric ganglion cells and mucosa. The injury usually heals as the baby grows, as long as adequate parenteral nutrition is provided.

Intact omphalocele

Infants with intact omphaloceles are usually not distressed; however, they should be carefully screened for associated problems, such as Beckwith-Wiedemann syndrome (which may cause hypoglycemia) or congenital heart disease, genetic abnormalities, or other malformations.

Maintenance intravenous (IV) fluids are administered, and the intact omphalocele sac is covered with a nonadherent dressing, such as Xeroform or Saran Wrap to preserve body heat and moisture.

Prophylactic antibiotics may be given preoperatively, if surgery for an associated intestinal anomaly is anticipated..

Closure of a small or moderate-sized omphalocele is usually accomplished without difficulty; however, infants with giant omphaloceles require staged surgery or "paint and wait", a nonoperative technique whereby topical antimicrobials are applied to the omphalocele sac (bacitracin or mupirocin), and the baby's torso is wrapped with an elastic bandage. This approach relies upon epithelialization of the omphalocele sac and wound contracture to obliterate the abdominal wall defect.

Ruptured omphalocele

When the omphalocele membrane is ruptured, the extruded viscera are placed in a silo, as with the case of gastroschisis.[28]

If a giant omphalocele is ruptured, it may be best to obtain closure utilizing biologic mesh (Alloderm or Surgisis)[39] sutured to the fascial margins of the defect. (See the image below.)

Closure of giant omphaloceles containing the liver is always challenging.[40, 41, 42] See the following images.

Gastroschisis

If the stomach is distended (from swallowed air), an orogastric tube should be placed to evacuate the air and succus intericus ("intestinal juice").

The eviscerated intestine should be placed over the abdominal wall defect, covered by Saran Wrap, and wrapped with dry Kerlix; the infant's lower torso may then be placed in a bowel bag. The baby may be placed in an incubator or under a radiant warmer, as long as the bowel is protected.

Administer broad-spectrum antibiotics because of the exposed intestine and open peritoneal cavity.

Anticipate and correct fluid, electrolyte, and heat losses: Administer an IV fluid bolus (20 mL/kg lactated Ringer or normal saline), followed by 5% dextrose/0.45 normal saline with potassium chloride (after having established the infant's urine output). Usually the baby's fluid requirements are greater than maintenance because of evaporative and third-space losses (within the lumen of the gut and interstitial tissues). Clinicians must carefully balance intake (IV fluids) and output (urine and gastrointestinal losses).

Urine output provides the most accurate measure of the adequacy of fluid resuscitation. Blood gas analysis identifies hypoperfusion and/or inadequate ventilation. Reduction of the herniated viscera is facilitated by evacuating meconium from the sigmoid colon and rectum.

Place a central venous line to provide parenteral nutrition, thereby minimizing catabolic protein loss during the period of gastrointestinal dysfunction.[33, 34, 35]

Consultations

Neonatologists and pediatric surgeons share the responsibility for the treatment of babies with abdominal wall defects.

Consultation with a cardiologist, pulmonologist, gastroenterologist, and geneticist may be indicated.

Midgut volvulus

A multi-institutional retrospective study identified 115 infants with omphalocele and 299 with gastroschisis, during the years 2000-2008.[43] Midgut volvulus occurred in 8 cases overall: 5 omphalocele babies and 3 gastroschisis babies. These authors advocate a Ladd procedure, concomitant with repair of an omphalocele.[43]

Omphalocele

Ambrose Pare, a 17th-century French surgeon, accurately described the adverse consequences of opening the omphalocele sac during closure of the abdominal wall defect.[44] He advocated squeezing the sac to reduce the herniated viscera and, if reduction was not possible, painting the sac with escharotic agents to promote epithelialization and wound contracture. However, healing is slow utilizing this technique, and during this time, the sac may rupture and the infant succumb to infection.

Healing is hastened by mobilizing skin flaps to cover the omphalocele sac (Gross technique); however, this results in the creation of a large ventral hernia.

In 1967, Schuster developed a more expeditious technique to close giant omphaloceles and large ventral hernias.[45] A circumferential incision is made along the perimeter of the omphalocele, leaving the sac intact to protect the herniated viscera. The incision is extended in the midline, exposing the rectus fascia from xiphoid to pubis. Silon (Teflon-reinforced Silastic) sheets are sutured to the rectus muscles and approximated in the midline over the omphalocele sac. Reduction is effected by gradually approximating the Silon sheets, which pulls the rectus muscles over the liver and intestines. When the ventral bulge is leveled, the Silon sheets are removed with the omphalocele sac; permanent closure is obtained by approximating the rectus fascia or sewing an elliptical patch to the fascia and then covering the patch with skin flaps. If this is not feasible, biologic mesh may be placed over the liver and intestines. Ultimately, the patch will be vascularized and support the ingrowth of epithelial cells. (See the image below.)

The use of a rigid patch is preferable (Gore-Tex, Surgisis).[39] The ellipse is tailored to give the anterior abdominal wall a concave appearance, lessening pressure upon the diaphragm. The patch is attached to the defect circumferentially: superiorly to the costal arch, inferiorly to the pubis, and laterally to the rectus fascia. Inflation of the lungs elevates the costal arch, which expands both the chest and the abdomen; the increased intra-abdominal pressure stretches the rectus muscles and stimulates their growth.

Dr Russell Jennings of Boston's Children's Hospital has developed an innovative technique whereby upward traction is applied to the silo housing the extruded viscera. The silo is firmly attached (sewn) to the circumference of the abdominal wall defect, and excess skin is attached to the silo. Upward traction stimulates growth of the abdominal wall over the extruded viscera, as opposed to pushing the extruded viscera into an undersized abdominal cavity.[46] (See the following images.)

Synthetic patches (Gore-Tex) require skin coverage or they will ultimately be rejected. Biologic mesh (Alloderm, acellular human dermis; or Surgisis, intestinal submucosa) provides a scaffold for ingrowth of autogenous cells; hence, the body does not perceive them as foreign, and they are not as prone to infection and rejection. Alloderm stretches, and the ultimate result is a large, but epithelialized protrusion that ultimately will require repair.[47, 48]

“Component separation” is a technique pioneered in adult patients to repair ventral hernias. Bilateral incisions are made along the Spigelian line (semilunar line) to allow medial displacement of the rectus fascia and closure of the abdominal wall defect. More recently, this technique has been utilized in children.[49]

See the images below.

Gastroschisis

In 1969, Allen and Wrenn adapted Schuster's technique to gastroschisis.[50] Silon (Dacron-reinforced Silastic) sheets are sutured to the full thickness of the abdominal wall defect and closed over the eviscerated intestine, creating a silo. Reduction is facilitated by stretching the abdominal musculature, emptying the stomach and bladder, and manually evacuating the colon. The silo is gently squeezed each day; usually a week is required to effect reduction of the extruded viscera. The critical factor is resolution of inflammation; in time, the stiff, congealed intestines become normal—soft and pliable—and can fit into the nooks and crannies of the abdominal cavity.[51, 52]

Adhesions may develop between the intestines and the silo or the abdominal wall defect. For this reason, Dr Jennings advocates applying Seprafilm over the intestines before placing the silo.[46]

Excessively tight closure of the abdominal cavity causes increased intra-abdominal pressure (abdominal compartment syndrome), which limits diaphragmatic excursion, impairing ventilation. Increased peak inspiratory pressure (PIP) is required, but this will decrease venous return. Increased heart rate is required to maintain cardiac output. If renal blood flow diminishes, glomerular filtration rate will also decrease, and urine output will fall; renal failure or renal vein thrombosis may ensue. Diminished mesenteric blood flow causes ischemia and augments the risk of necrotizing enterocolitis (NEC), because dysmotility leads to stagnation and bacterial overgrowth, and the bowel is immunologically immature.[53]

Avoid PIPs greater than 25 mm Hg. High-frequency oscillatory ventilation is an alternative to conventional ventilation, if intra-abdominal pressures are markedly increased.[54]

The intra-abdominal pressure is measured by connecting a manometer to a Foley catheter or a nasogastric tube. The central venous pressure, intravesical pressure, and the intragastric pressure should not exceed 20 cm H2O to avoid development of abdominal compartment syndrome.[24]

Alternate ways of managing infants with abdominal wall defects generate lively discussion among colleagues. When disparate techniques yield equivalent results, when no technique is demonstrably superior, personal preference is determinative.

The dilemma is balancing the goal of replacing the extruded viscera and closing the abdomen against the attendant complications, most notably abdominal compartment syndrome, which follows the degree of viscera-abdominal disproportion. Minimizing intra-abdominal hypertension (IAH) is critical.

An intra-abdominal pressure above 15 mm Hg is high; that exceeding 20 mm Hg is excessive and likely to precipitate abdominal compartment syndrome. The effects of IAH are both hemodynamic and ventilatory. Reduced cardiac output diminishes splanchnic and renal perfusion, which leads to oliguria and gut acidosis. Hypoventilation (hypercarbia and hypoxia) compounds the metabolic acidosis. Abdominal compartment syndrome has devastating physiologic complications, including renal failure, sepsis, bowel ischemia, and wound complications.

Bowel ischemia leads to NEC, which may cause short-bowel syndrome. Wound complications include dehiscence, sepsis, and enterocutaneous fistulae. Excessively tight closure of gastroschisis may be a factor in as many as 75% of patients referred for intestinal transplantation.[55]

Controversial issues include the following:

• Should these infants be delivered by cesarean delivery or vaginally?

• Should a prefabricated silo be placed in the neonatal intensive care unit (NICU) with sedation, or in the operating room (OR) under general anesthesia? Does it matter?

• Can the intestines be more thoroughly cleansed and the anatomy better assessed in the OR rather than in the NICU?

• Are "off the shelf" silos preferable to those fabricated by the surgeon from Silon sheets?

• Does stretching the flaccid (paralyzed) abdominal wall enlarge the abdominal cavity?

• Is enterolysis of the inflamed intestine, cutting through the inflammatory peel and separating the congealed loops of intestine feasible, or is the risk of damaging the intestine prohibitive?

• Should an attempt be made to evacuate meconium from the intestine?

• Does squeezing the intestine injure the serosa and promote the formation of adhesions?

• Should the appendix be removed and the opening in the cecum used to evacuate the meconium?

• Should the surgeon dilate the anus and milk the meconium through the colon into the rectum and out the anal canal?

• If a silo is placed, should pressure be applied to the eviscerated intestine, and does this pressure enlarge the abdominal cavity as opposed to the Jennings approach?

• Is resolution of inflammation the determinative factor in achieving reduction? Is squeezing the silo necessary? Simply allowing the intestine to sink by gravity into the abdominal cavity may be sufficient.

• When should a silo be removed to minimize the risk of infection?

• Which antibiotics should be used?

• Should the antibiotic cover gut or skin flora?

Many surgeons favor placement of a prefabricated silo in the nursery with gradual reduction of the extruded intestine. Criteria that preclude this technique include poor bowel perfusion (a small, constricting defect), or bowel and/or mesentery attached to the abdominal wall defect, gross viscera-abdominal disproportion, and deteriorating metabolic acidosis.[55, 56]

Vigilance is necessary during reduction to ensure that the intestines are actually moving into the peritoneal cavity as the silo is squeezed. Otherwise, bowel loops may be compacted together or pressed against the ring of the silo or the margins of the defect, causing congestion or ischemia. Any sign of venous congestion mandates removal of the silo and inspection of the intestines. Necrosis of the duodenum from the ring of the silo abutting its anterior wall has been reported.[56] (See the image below.)

The baby in the image above is truly remarkable. She was born with jejunal atresia and necrosis of the distal small intestine and necrosis of the antimesenteric aspect of the atretic jejunum. This was excised, and the remaining intestine was tubularized. Ultimately, it became dilated; we utilized the serial transverse enteroplasty (STEP) procedure[57] and created an anastomosis to the distal microcolon. Anastomotic stricture occurred and required several revisions, but each time the proximal intestine dilated, making it amenable to additional STEP procedures. This infant was referred for an intestinal transplantation, which proved to not be necessary.

See the images below.

Bladder exstrophy

Surgical repair of bladder exstrophy aims to preserve kidney function. Surgical reconstruction involves the following:

• The bladder is dissected away from its attachments to the lower abdominal wall and folded upon itself.

• Closure of the lower abdominal wall defect necessitates creating a space for the bladder and other pelvic organs.

• The shape of the pelvis must be altered, from flat and shallow to concave.

• The intersymphyseal band between the splayed pubic symphysis is divided, and the anterolateral pelvic bones are rotated medially. If left untreated, affected children have a waddling gait because of the "down-and-out" rotation of the anterior pelvic ring and diastasis of the pubic symphysis.

• Urinary continence and voluntary micturition is obtained by early closure of the bladder and reconstruction of the bladder neck and urethra.

• Vesicoureteral reflux is usually present and requires antibiotics and, perhaps, ureteral reimplantation.

• Finally, epispadias is corrected, to achieve adequate genitourinary function.

See the images below.

Prune-belly syndrome

Operative procedures to correct prune-belly syndrome include the following:

• Reconstruction of the abdominal wall (especially the lower portion)

• Repair of the urinary collecting system (megaureters and megacystis)

• Performance of bilateral orchiopexies

Cloacal exstrophy

Repair of cloacal exstrophy includes the following:

• Reduction of the prolapsed ileum (the "elephant trunk")

• Separation of the flayed-open cecum from the central portion of the bifid bladder; this placode of cecum is tubularized

• Approximation and repair of the bladder halves as in bladder exstrophy

• Later, mobilization and anastomosis of the colostomy to the rudimentary hind gut and creation of a stoma; or an anus may be reconstructed by posterior sagittal anorectoplasty[58]

See the images below.

Diet

Infants with omphaloceles have normal intestine and do not require special formulas. The occasional intestinal atresia, perhaps associated with a patent omphalomesenteric duct, is not usually associated with short gut.

Those with gastroschisis, however, may have sustained injury to the intestine and thus may require elemental formulas or protein hydrolysates with lactose-free carbohydrates, or medium-chain triglycerides.

Babies with short-gut syndrome absorb medium-chain triglycerides more readily than long-chain triglycerides; paradoxically, the latter are more valuable with regard to gut adaptation.

Activity

The liver of a child with a repaired giant omphalocele is located in the epigastrium, where it is more vulnerable to trauma. Therefore, these children should avoid contact sports.

Following discharge, these infants require close follow-up to assess their growth and weight gain, and to chronicle developmental milestones.

They frequently have symptoms of gastroesophageal reflux (GER), which are notoriously variable, and which may occasionally be life-threatening. Treatment for GER follows the same principles as for other infants.

Hirschsprung disease may also occur. Physicians should consider this diagnosis in a child with refractory constipation and failure to thrive.