GastroschisisClinical PresentationGastroschisis represents a congenital defect characterized by a defect in the anterior abdominal wall through which the intestinal contents freely protrude. Unlike the omphalocele, there is no overlying sac and the size of the defect is much smaller (. Chapter 38. Pediatric Surgery. Eigth Edition. New York : Mc Graw-Hill Companies.
Gastroschisis and omphaloceleDescription and embryonic originAlthough gastroschisis and omphalocele both result fromabdominal wall defects, these rare disorders are distinct entities(see Chapter 121). The incidence of gastroschisis is between0.4 and 4 per 10 000 live births, and omphalocele is 1.53 per10 000 births [158,159].In omphalocele, the abdominal viscera herniate throughthe umbilical ring and persist outside the body, covered bya membranous sac but not by skin. In gastroschisis, massiveevisceration of the intestines occurs through a small defect inthe abdominal wall, usually to the right of the closed umbilicalring. The bowel has no membranous covering, has beenexposed to amniotic fluid in utero, and is often matted, thickened,foreshortened, and covered with adhesions. It hasbeen hypothesized that omphalocele is caused by a failureof embryonic folding at the level of the lateral folds or persistenceof the body stalk [158,160]. Gastroschisis may becaused by vascular disruption in utero, leading to failure ofdifferentiation of the somatopleural mesenchyme, or laterbetween the time of herniation into the umbilical cord andfixation, or by disruption of the right omphalomesentericartery. The defect is thought to occur between the fifth andtenth weeks of gestation, but perinatal insults have also beensuggested in patients in whom gastroschisis was not detectedsonographically [161]. Potential teratogens include tobacco,alcohol, cocaine, and other drugs [159].Other congenital anomalies that occur in associationwith omphalocele are chromosomal; about one-third of casesof omphalocele with multiple anomalies have trisomy 13,trisomy 18, or the BeckwithWiedemann syndrome, whichis characterized by macroglossia, large infant size, visceromegaly,early hypoglycemia, and increased risk of Wilmsand other tumors. Gastroschisis is associated with intestinalanomalies, including atresia and malrotation, vascular disruptions,and renal and gallbladder agenesis [158]. Severalmouse models of gastroschisis have been described [162166].In mice that are null for the bone morphogenetic protein 1(Bmp1) gene, the Alx4 gene, or the aortic carboxypeptidaselikeprotein gene, gastroschisis develops with early mortality.The ALX4 protein is a homeodomain transcription factor.Both BMP1 and the aortic carboxypeptidase-like proteinappear to have important functions in the extracellularmatrix. The relevance of these gene defects to human diseaseis unclear; a mutational analysis of the BMP1 gene in humanpatients with gastroschisis was unrevealing [167]. Mousemodels of omphalocoele have also been described [162], inmouse knockouts of insulin-like growth factor 2 (IGF-2), calreticulin,and several transcription factors. The transforminggrowth factor- (TGF-) signaling pathway has been implicatedas important in ventral body wall closure [162].Prenatal diagnosisElevated levels of maternal serum -fetoprotein are associatedwith ventral abdominal wall defects. Gastroschisis isdetected with greater sensitivity than omphalocele [160].Improvements in the accuracy of prenatal ultrasonographyhave led to more frequent detection [158,159,168]. One ofthe major advantages of prenatal diagnosis is that the obstetricianis alerted, so that at the time of delivery the mothercan be taken to a tertiary care center where appropriate surgicaland neonatal intensive care support is available [160].The role of preterm delivery to minimize intestinal damageand prevent intrauterine death is still unclear, and the factorsthat determine the need for this intervention are still beingdefined [169,170]. Intensive monitoring with ultrasonographyhas been utilized to determine when preterm deliverymay be indicated, and this strategy appears to improvesurvival [170172]. Recommendations for the appropriatemode of delivery (e.g., trial of labor vs elective cesareansection) are being debated [172176], although it is clear thatthe rate of abdominal delivery is high because of peripartumcomplications [177].TreatmentSurgical closure of omphalocele and gastroschisis is attemptedshortly after birth. Primary closure may be possible with theuse of retention sutures and stretching the abdominal wall. Ifthis cannot be achieved, a silo or Silastic sac can be used withsuccessive compression to reduce the herniation further. Thedecision to use a silo and a staged procedure may be based onintraoperative bladder or intragastric pressure measurementsthat reflect the intraabdominal pressure [169,178]. Carefulregulation of the intraabdominal pressure is critical for successfulrepair; high pressures that lead to respiratory distressand intestinal and renal ischemia the major causes of morbidityand mortality must be avoided. The material is placedover the herniated bowel or sac and reduced manually andserially sutured to reintroduce the bowel into the abdominalcavity. A comparison of primary emergent closure vs closurefollowing reduction with a spring-loaded silo (for gastroschisis)suggested that silos improve the overall outcome [179].Because almost all children have bowel hypomotility, totalparenteral nutrition is recommended early in the course ofthe illness.Advances in surgical correction have greatly improved theprognosis of patients with gastroschisis, despite the fact thatthe bowel is usually damaged and slow to return to normalfunction. Survival rates range from 70% to more than 90%[173,180]. The presence of necrotizing enterocolitis andother anomalies (affecting other organs) or associated intestinalconditions (e.g., atresias, perforations, necrotic segments,volvulus) affects mortality rates [173,181]. In the absenceof severe associated anomalies, the immediate survival andlong-term outcome of patients with omphalocele have alsoimproved in the past several years [182,183]. Survival is alsorelated to the severity of the associated anomalies and medicalconditionsYamada T, Alpera D, Anthony K, et. al. Textbook Of Gastroenterology. Fifth Edition Volume 1. Oxford : Blackwekk Publishing. Page 1118-1119
Figure 46.4 Neonate with gastroschisis and marked intrauterinegrowth retardation. The defect is to the right of the umbilicalcord root. The protruding intestine is oedematous andmatted.GastroschisisGastroschisis (Fig. 46.4) is an abnormality where theintestine is seen to protrude through the abdominal wall,usually to the right of the umbilicus. Unlike exomphalos,where the protruding viscera are covered by a membrane,in gastroschisis the protruding bowel floats freely and assuch is prone to direct injury.Most cases of gastroschisis are detected antenatally.Maternal serum a-fetoprotein level is elevated, promptinga detailed ultrasound scan to be performed. Normalvaginal delivery close to term is preferred, but one-third ofthose affected will require a Caesarian section for obstetricindications and a further one-third require an emergencyCaesarian section for fetal distress during labour.Following delivery, the neonate with gastroschisis isresuscitated and the exposed intestine is covered withsandwich wrap or similar. This has the benefits of keepingthe bowel moist and limiting heat loss. As soon as is practical(and preferably within 4-6 h of birth), the baby istaken to the operating theatre where the intestine isreplaced in the abdominal cavity. This is achievable inover 80% of cases. In the remainder, a Silastic silo isfashioned and sutured to the abdominal wall. In the followingweek or so, the intestinal contents are graduallyeased into the abdominal cavity and the abdominal wall isclosed at a second operation.Approximately 25% of neonates with gastroschisishave associated bowel injury (e.g. atresia, stenosis orischaemia). Other associated congenital anomalies areuncommon. The most important postsurgical problemfacing these babies is that they suffer from a protractedileus. Parenteral nutrition is required to allow the baby togrow and to help the abdominal wall heal. As a consequenceof improvements in neonatal critical care andnutrition, over 90% of neonates with gastroschisis survive after treatment.
Cuschieri A, Grace P, et al. 1996. Clinical Surgery Second Edition. Autralia : Blackwell Science. Page 785
GastroschisisGastroschisis occurs with an incidence rate of 1 in 3,000 to 8,000 live births, and for unknown reasons, the incidence rate is increasing. Infants with gastroschisis tend to be born prematurely, have lower birth weights, and have younger mothers.1,2 Familial cases of gastroschisis have been reported and are distinctly rare.3 Associated congenital anomalies are uncommon and occur in about 10% of cases, most commonly intestinal atresia or stenosis. These anomalies are thought to reflect mechanical or vascular compromise to the herniated bowel. Rarely, infants with gastroschisis have complete loss of small bowel secondary to in utero volvulus
The pathophysiology of gastroschisis remains unknown. In normal fetal development, there are two paired umbilical veins; as the intestine returns to the abdominal cavity through the umbilicus, the right umbilical vein undergoes resorption, leaving the left umbilical vein intact. Weakness of the umbilical membrane at the site of umbilical vein resorption may evolve into a hernia, and, in the case of membrane rupture, evisceration of the intestine through the defect may occur. This explanation is consistent with the clinical observation that the abdominal wall defect in gastroschisis almost always is located to the right of the umbilicus. With the advent of routine antenatal ultrasonography, the sequential development of a typical gastroschisis has been documented as a consequence of a ruptured hernia of the umbilical cord in utero.4 Therefore, this observation suggests that gastroschisis is an isolated mechanical defect of the developing umbilical cord rather than a global defect in embryogenesis.The amount of bowel eviscerated in gastroschisis can be extensive because the bowel has not undergone complete mesenteric rotation and fixation. Typically, the bowel is thickened and the mesentery may be foreshortened secondary to the inflammatory response induced by direct exposure to amniotic fluid. Given the typical small size of the abdominal wall defect, herniation of the liver in gastroschisis is distinctly unusual (Fig. 110.1).
OmphaloceleAnatomy, Embryology, and PathophysiologyThe incidence rate of omphalocele is estimated to be 1 in 6,000 to 10,000 live births and has been stable over the past several decades. Omphalocele is an abdominal wall defect of varying size that is characterized by the presence of herniated visceral contents into a translucent sac. The sac is composed of amniotic membrane, mesenchymal tissue known as P.1879
Wharton's jelly, and peritoneum. The umbilical cord typically attaches to the sac and may be eccentric in origin (Fig. 110.2). The sac may be inadvertently ruptured before or during delivery, but it is always present. Similar to gastroschisis, intestinal malrotation is present. Unlike gastroschisis, the bowel is typically normal in appearance because it has not been directly exposed to the amniotic fluid. Small omphaloceles are typically abdominal wall defects 2 to 5 cm in diameter and may have only a small amount of herniated bowel within the sac. Giant omphaloceles larger than 10 cm in diameter can lead to massive and extensive herniation of the stomach, bowel, liver, and spleen, with subsequent underdevelopment of the abdominal cavity (Fig. 110.3).
Omphalocele is a result of incomplete closure of the anterior abdominal wall at the umbilicus during embryogenesis. During week 4 of gestation, the midgut undergoes progressive elongation in the yolk sac outside the embryonic coelomic cavity. The midgut returns to the abdominal cavity during week 10 of gestation, where it undergoes normal rotation and fixation of its mesentery to the posterior abdominal wall. Normal closure of the anterior abdominal wall requires return of the midgut to the abdominal cavity, along with growth and fusion of the anterior body folds (cephalic, caudal, and two lateral) at the base of the umbilicus. Failure of growth, migration, or fusion of the lateral body folds leads to omphalocele. Failure of growth and fusion of the cephalic folds may lead to either a supraumbilical omphalocele associated with a midline sternal defect and a herniated heart, termed ectopia cordis, or a constellation of defects known as the pentalogy of Cantrell.5 This sequence includes a sternal cleft, an absence of the septum transversum of the diaphragm, a pericardial defect, a cardiac defect, and an epigastric omphalocele (Fig. 110.4). Infants born with either ectopia cordis or pentalogy of Cantrell have significant morbidity, and often these conditions are lethal. Associated anomalies are much more common in infants with omphalocele than with gastroschisis, reflecting the more global abnormality of embryogenesis in omphalocele compared with the simple mechanical defect in gastroschisis. About 50% to 60% of infants with omphalocele have at least one associated congenital anomaly.6,7 These infants are at moderate to high risk for anomalies of the skeleton, gastrointestinal tract, nervous system, genitourinary system, and cardiopulmonary system. In addition, infants with omphalocele have a higher incidence of chromosomal abnormalities and other conditions, such as Beckwith-Wiedemann syndrome. A comparison of gastroschisis and omphalocele is summarized in Table 110.1.
Perioperative Management for Gastroschisis and OmphaloceleIn the absence of fetal distress, whether elective cesarean section improves neonatal outcome in infants with gastroschisis or omphalocele remains controversial.8,9 Some investigators advocate elective delivery of infants with gastroschisis following the establishment of lung maturity. A prospective study that alternated vaginal delivery with elective cesarean section for infants with gastroschisis demonstrated no significant differences in outcome.10 To prevent birth-related hepatic injury, cesarean section is preferable for prenatally diagnosed infants with giant omphaloceles.After delivery, infants with either gastroschisis or omphalocele have similar initial management priorities. Attention must be given to the establishment of an adequate airway with effective ventilation and oxygenation. The infant should be maintained under either an external warmer or a humidified incubator. A nasogastric or orogastric sump tube should be inserted early and placed on suction to prevent further intestinal distention. The herniated viscera should be covered with warm, saline-soaked gauze and covered with plastic wrap to prevent further contamination; this maneuver also helps to prevent hypothermia and volume depletion. Alternatively, the infant's entire lower torso can be placed inside a plastic bowel bag. Regardless of the method, the initial therapeutic goal is to provide rapid, effective temporary coverage of the viscera. Adequate support of the herniated viscera must be provided to prevent intestinal ischemia. With large omphaloceles, the position of the infant's liver and viscera may impair venous return from the inferior vena cava when the infant is supine, and these infants may preferentially require a left-side-down position to maintain hemodynamic stability. An intravenous catheter should be placed early, and 10% intravenous dextrose, along with broad-spectrum antibiotics, should be administered. Infants with gastroschisis may have higher intravenous fluid requirements secondary to the inflammatory nature of the intestine. If the infant is not delivered at a center where definitive surgical care can be provided, urgent transport should be arranged
Given the high incidence of associated anomalies, infants with an intact omphalocele should undergo diagnostic investigation preoperatively, guided by the clinical presentation and physical examination of the infant. These studies include a chest film, echocardiogram, and renal ultrasound, in addition to baseline blood work. Until the decision is made with respect to the timing and method of repair, the omphalocele should remain covered and protected with a dressing. If the omphalocele is ruptured or torn, immediate closure or coverage is necessary.Once the infant has been stabilized and assessment for other anomalies is complete, the infant is taken to the operating room for correction of the abdominal wall defect. Reduction of the herniated viscera with primary fascial closure of the abdominal wall is an achievable goal in approximately 60% to 70% of infants with either gastroschisis or omphalocele. Gentle but definitive stretching of the abdominal wall is performed, and proximal decompression of the bowel is maintained with nasogastric or orogastric decompression. The defect may require enlargement to evaluate fully the intestinal tract. With omphalocele, the sac is usually resected. The limiting factor in primary closure of an abdominal wall defect is the increased intraabdominal pressure generated by the reduction of the herniated viscera. Increased intraabdominal pressure can lead to a clinical situation known as abdominal compartment syndrome. Features of neonatal abdominal compartment syndrome include impaired venous return caused by compression of the inferior vena cava, reduction of sphlanic blood flow leading to mesenteric ischemia, and respiratory compromise secondary to impaired diaphragmatic excursion. Intraoperative measurement of intragastric or intravesical pressure, end-tidal CO2, or central venous pressure may be helpful in determining the safety of primary abdominal wall closure.11 If the herniated viscera cannot be reduced primarily, a Silastic pouch or silo is constructed and daily partial reduction of the silo is performed. This technique allows more gradual reduction of the herniated viscera into the abdominal cavity, and complete reduction usually is obtained within 3 to 7 days. The infant then can return to the operating room for removal of the temporary silo with delayed primary closure of the abdominal wall defect (Fig. 110.5). Staged closure of gastroschisis using commercially available Silastic silos has been reported to decrease the risk of long-term bowel dysfunction and need for reoperation by avoiding abdominal compartment syndrome.12 Alternatively, a large abdominal wall defect may be covered with abdominal skin flaps with delayed repair of the ventral hernia months to years later.
Infants with giant omphaloceles may also be managed nonoperatively. The sac can be physically supported and left intact, allowing epithelialization of the sac over several weeks to months. Antibiotic solutions or ointments are usually applied to control desiccation. Delayed repair of the ventral hernia is required. This delay is particularly useful in the infant with a giant omphalocele and a small, underdeveloped abdominal cavity that prohibits primary closure.Infants with repaired omphalocele usually have relatively prompt return of bowel function after definitive repair. In comparison, nearly all infants with gastroschisis have a delay in intestinal function following closure. The use of total parenteral nutrition (TPN) is essential in the treatment of these infants because it allows nutritional support while the bowel inflammatory process resolves. It is not unusual for these infants to require up to 4 weeks after repair to have bowel function normalize, and time taken to achieve full enteral feeding is not affected by the use of erythromycin as a prokinetic agent.13 Approximately 15% oinfants with gastroschisis develop necrotizing enterocolitis (NEC), a diffuse, often life-threatening inflammatory complication of the neonatal intestinal tract.14 In addition, infants with gastroschisis are at risk for nutrient malabsorbtion and intestinal dysmotility with inability to tolerate full enteral feeding. This latter situation can evolve into a long-term condition termed pseudoobstruction and may require long-term, sometimes lifelong, dependence on TPN for caloric intake.Long-term outcome of infants operated on for gastroschisis or omphalocele is usually dependent on the morbidity and mortality of associated conditions rather than the abdominal wall defect itself. Surgical conditions such as undescended testicles, Meckel's diverticulum, and adhesive small bowel obstruction are encountered with moderate frequency. Most children with repaired abdominal wall defects enjoy satisfactory health and quality of life, although they have been reported to have a lower degree of physical fitness measured by exercise time and maximal oxygen consumption.15
Mulholland M, Lillemoe K, Doherty G,et al. 2006. Greenfields Surgery Scientific Principles and Practice. Fourth Edition. Lippincontt Williams & Wilkins. Chapter 110.
Abdominal Wall Defects Defects of the anterior abdominal wall are a relatively frequent anomaly managed by pediatric surgeons. During normal development of the human embryo, the midgut herniates outward through the umbilical ring and continues to grow. By the 11th week of gestation, the midgut returns back into the abdominal cavity and undergoes normal rotation and fixation, along with closure of the umbilical ring. If the intestine fails to return, the infant is born with abdominal contents protruding directly through the umbilical ring, termed an omphalocele ( Fig. 71-14A ). Most commonly, a sac is still covering the bowel, thus protecting it from the surrounding amniotic fluid. Occasionally, the sac may be torn at some point in utero, creating confusion with the other major type of abdominal wall defect termed gastroschisis (see Fig. 71-14B ). In contrast with omphalocele, the defect seen with gastroschisis is always on the right side of the umbilical ring with an intact umbilical cord, and there is never a sac covering the abdominal contents. Major morbidity and mortality with either anomaly are not as high with surgical repair of the abdominal defect as with the associated abnormalities. In the absence of other major anomalies, long-term survival is excellent.[31]
Omphalocele The abdominal contents with an omphalocele are covered with a membrane composed of the peritoneum on the inside and amnion on the outside. The size of the defect is variable, ranging from a small opening through which a small portion of the intestine is herniated to a large one in which the entire bowel and liver are included. In contrast with gastroschisis, karyotype abnormalities are present in roughly 30% of infants, including trisomies 13, 18, and 21. More than half of infants with omphalocele have other major or minor malformations, with cardiac being the most common, followed by musculoskeletal, gastrointestinal, and genitourinary. There is also a close association with Beckwith-Wiedemann syndrome (omphalocele, hyperinsulinemia, and macroglossiaPreoperative Evaluation and Management The immediate treatment of an omphalocele consists of nasogastric or orogastric tube decompression for prevention of visceral distention due to swallowed air. An IV line is secured for administration of fluids and broad-spectrum antibiotics. The sac is covered with a sterile, moist dressing and the infant transported to a tertiary care pediatric surgery facility. Before operative repair, the infant is evaluated for potential chromosomal and developmental anomalies by a careful physical examination, plain chest radiograph, echocardiography if the physical examination suggests underlying congenital heart disease, and renal ultrasonography. Because the viscera are covered by a sac, operative repair of the defect may be delayed to allow thorough evaluation of the infant.Surgical Management Several options exist for the surgical management of an omphalocele and are largely dictated by the size of the defect. In most cases, the contents within the sac are reduced back into the abdomen, the sac is excised with care to individually ligate the umbilical vessels, and the fascia and skin are closed. Fascial closure may be facilitated by stretching the anterior abdominal wall as well as milking out the contents of the bowel proximally and distally.In giant omphaloceles, the degree of visceroabdominal disproportion prevents primary closure, and the operative management becomes more challenging. Construction of a Silastic silo allows for gradual reduction of the viscera into the abdominal cavity over a several-day period. Monitoring of intra-abdominal pressure during reduction may prevent the development of an abdominal compartment syndrome. After the abdominal contents are returned to the abdomen, the infant is taken back to the operating room for formal fascia and skin closure. Occasionally, closure of the fascia may be impossible. In these cases, the skin is closed, and a large hernia is accepted. This is repaired after 1 or 2 years. When the skin cannot be closed over the defect, several options exist, including the topical application of an antimicrobial solution to the outside of the sac, such as silver nitrate or silver sulfadiazine. Over time, this will result in granulation tissue and subsequent epithelialization of the sac. A repair of the large hernia is then performed a few years after this.
Gastroschisis In contrast to patients with an omphalocele, the risk for associated anomalies with gastroschisis is low. One major exception to this general rule is the association of gastroschisis with intestinal atresia, which may be present in up to 15%. Atresias may involve the small and large intestine. The cause of gastroschisis is presently unknown, but a prevailing theory is that it results from an abdominal wall defect associated with normal involution of the second umbilical vein. In addition, babies with gastroschisis are more often small for gestational age and born to mothers with a history of cigarette, alcohol, and recreational drug use and intake of aspirin, ibuprofen, and pseudoephedrine during the first trimester; there is also an 11-fold increase in risk in mothers younger than 20 years.The surgical management of gastroschisis is similar to omphalocele. Considerations for third-space fluid losses from the exposed intestine and risk for infection dictate more expedient coverage. The presence of atresia in a patient with gastroschisis may be managed in a number of ways. The bowel can simply be placed into the abdomen with a planned reoperation after several weeks. Another approach would be to perform a proximal diverting stoma. Finally, a primary anastomosis may be attempted. This is rarely advised because of the possibility of other atresias as well as the overall condition of the bowel.In patients with gastroschisis, the intestine is often thickened, edematous, matted together, and foreshortened. It is unclear whether this represents damage from the amniotic fluid or ischemia from the small, constricting abdominal wall defect. The short gut syndrome may be a consequence of the attenuated intestinal length. Even with adequate length, the remnant bowel may be damaged to the point that motility, digestion, and absorption are markedly impaired. This prenatal intestinal injury accounts for most of the postoperative morbidity and mortality. Virtually all infants have a prolonged postoperative ileus. Parenteral nutrition is lifesaving but is also associated with the development of cholestasis, cirrhosis, portal hypertension, and ultimate liver failure.Townsend, Beauchamp, Evers, Mattox. 2007. Sabiston Textbook Of Surgery. The Biological Basis Of Modern Surgical Practice. Chapter 71. Pediatric Surgery. Section XII. Elsevier Inc
