The two most common congenital wall defects are gastroschisis and omphalocele.
Gastroschisis
Definition
Gastroschisis is a full-thickness, typically right-sided, paraumbilical abdominal wall defect and primarily has the intestines and stomach protruding through the defect in the amniotic fluid.
Incidence
There has been a 10- to 20-fold increase in the birth prevalence of gastroschisis over the past two decades. The cause of this increase is poorly understood, but is a worldwide phenomenon.
Currently, Gastroschisis occurs in one in 4000 live births.
Gastroschisis occurs in males and females equally.
Pathophysiology
The etiology of gastroschisis has yet to be determined.
There are several embryologic hypotheses that describe abnormal formation or weakening of the body wall followed by bowel herniation.
The current accepted theory is that of failure of migration of the ventral folds on the right side causing the defect.
Risk factors
Gastroschisis has been strongly associated with maternal age younger than 21.
Nulliparity has been associated with gastroschisis, independent of maternal age.
Maternal exposure to vasoconstrictive drugs (cocaine, ephedrine, and pseudoephedrine), tobacco, aspirin, and ibuprofen may be associated with the development of gastroschisis.
Maternal low bodyweight and genitourinary infections may also be associated with a greater risk of gastroschisis.
Conversely, acetaminophen use in the first trimester may decrease the risk of gastroschisis.
Clinical presentation
Majority of patients are diagnosed prenatally in the United States.
Gastroschisis may first be identified by an elevated second trimester maternal serum α-fetoprotein level. An elevated maternal serum α-fetoprotein should be investigated further with a level 3 fetal ultrasound.
At 10 weeks of gestation, the midgut returns to the abdominal cavity, after this time point gastroschisis may be diagnosed with ultrasonography by visualization of freely floating intestine and a paraumbilical abdominal wall defect that is typically located to the right of the midline.
Gastroschisis may be associated with oligohydramniosis; polyhydramnios is less common and is associated with fetal bowel obstruction (atresia) or reduced bowel motility.
Bowel dilation is considered to be a prognostic marker for worse clinical outcome but has not been proven.
It may be challenging to differentiate a gastroschisis from a ruptured omphalocele prenatally.
At birth, the intestines are noted to be outside the abdomen and are in varying degrees of being “matted” or thickened.
It is not uncommon to see these intestines to have meconium staining.
The ring in the abdominal wall may be excessively tight and the intestines may appear ischemic at times due to that.
Gastroschisis is labeled “complex” when there are additional intestinal abnormalities or ischemia and “simple” when it occurs in isolation.
The most common associated anomaly in gastroschisis is bowel atresia, with a reported rate of 6.9% to 28%. Gastroschisis is rarely associated with extraintestinal malformations.
Diagnosis
Gastroschisis is diagnosed clinically, as described above.
Management
Perinatal care
Advocates for cesarean delivery for fetuses with gastroschisis contend that vaginal delivery may injure the exposed bowel or increase the risk for infection. However, there is no proven benefit of cesarean section over vaginal delivery for fetuses with gastroschisis. Therefore, the recommendation is vaginal delivery at a center that is equipped to handle pediatric surgical cases.
Amniotic fluid cytokines, proinflammatory mediators, and digestive compounds may contribute to bowel inflammation and injury in fetuses with gastroschisis. Based on experimental animal data where the intestinal condition was improved with decreased duration of exposure to amniotic fluid, preterm delivery has been offered to improve the outcome in gastroschisis. Human studies for planned preterm delivery are inconclusive and currently not recommended due to the negative effect of low birth weight and prematurity with respiratory issues on outcome.
Neonatal medical management
Upon delivery, the bowel should be covered in warm, saline-soaked gauze and placed in the center of the abdomen. The baby should be placed on the right side to prevent the mesentery from kinking.
Intravenous access must be secured and appropriate fluid resuscitation initiated immediately following delivery, as a neonate with gastroschisis will have evaporative water losses from the exposed bowel.
The baby should also be partially wrapped in plastic wrap (“bowel bag”) to stabilize the temperature and decrease evaporative losses. Alternatively, a preformed silo may be applied in the delivery room.
A nasogastric tube must also be placed to decompress the bowel.
A complete physical examination should be performed, with a detailed examination of the bowel to evaluate for intestinal ischemia, perforation, or atresia.
Neonatal surgical management
The goal of surgery is to return the bowel into the peritoneal cavity, treat associated anomalies, and close the abdominal wall defect, while minimizing the risk of morbidity. Prior to surgery, the bowel must first be examined for obstructing bands, atresia, or perforation. Closure may be performed in a primary or staged fashion.
Obstructive bands need to be lysed prior to primary or staged closure.
The thickness of the peel surrounding the bowel is often too thick and inflamed to allow for a safe immediate anastomosis.
In the case of a proximal atresia, the bowel is reduced into the abdomen, and then a delayed repair is performed in 3 to 5 weeks to allow the intestine to become normal and make anastomosis easier. During this time the baby is receiving parenteral nutrition, and, therefore, a PICC line or central venous access is required in all babies with gastroschisis.
For a distal atresia, an ostomy may be created and the baby may receive enteral nutrition while waiting for the bowel to normalize.
Primary reduction and closure
Primary reduction and abdominal wall closure is advocated when there is sufficient intraabdominal domain so that closure will not result in the development of abdominal compartment syndrome and cause complications. This can be accomplished safely in a fair number of newborns.
Staged reduction and closure
Staged reduction of the intestines is often performed with the use of a preformed plastic silo with a circular spring that is placed inside the abdominal wall defect (Figure 34-1).
The bowel is then slowly reduced by sequential ligation of the silo (Figure 34-2).
Abdominal wall closure is performed once the bowel is completely reduced, which usually takes 3 to 5 days.
Care must be exercised to ensure that the intestines remain viable and well perfused during the reduction.
The data for immediate versus delayed or staged closure are inconclusive with regards to outcome.
Abdominal wall closure
Primary fascial closure is performed when possible. However, recent studies and reports of experience at single centers document good outcomes with skin closure only.
Cosmetic outcome may be improved by using a purse-string suture technique in the skin around the umbilicus to create a circular scar.
Alternatively, when available, the umbilical cord may be utilized to fill the gastroschisis defect and a dressing is applied with subsequent closure within a few days.
Postoperative care
The bowel inflammation associated with gastroschisis is often associated with delayed tolerance of enteral feeds due to dysmotility. This may last from 1 to 4 weeks before feedings can be introduced and subsequently advanced.
A decrease in the amount of nasogastric tube output as well as change in color from bilious to more clear and bowel movements are used as markers of resumption of intestinal activity.
While awaiting return of bowel function, treatment includes nasogastric decompression and parenteral nutrition.
There is a higher than expected rate of necrotizing enterocolitis/pneumatosis intestinalis in patients with gastroschisis. A majority of these cases do not require operative intervention and resolve with antibiotics, parenteral nutrition, and bowel rest.
Early developmental/therapeutic interventions
Feeding
While awaiting return of bowel function, it is important to initiate oral stimulation therapy early so that the sucking-swallowing reflex is not lost.
We recommend the storing of maternal breast milk to be used as the first feeds when the neonate can tolerate them.
Growth
A large number of babies with gastroschisis are small for gestational age; however unlike other SGA babies due to IUGR, the prognosis is not affected and they catch up growth to their cohort by a year or two of life.
Motor development
Central hypotonia and core muscle weakness is expected due to length of time in supine, nonswaddled positioning, as well as surgical history.
Physical therapy services should be initiated as soon as the infant is stable.
Prognosis
Simple gastroschisis patients have a remarkably good prognosis with over 96% survival to discharge with modern NICU and parenteral nutrition care.
Patients with complex gastroschisis (gastroschisis plus additional intestinal anomalies, or ischemia) have increased morbidity and mortality and a longer hospital stay depending upon the anomaly and need for further operative intervention.
These complex patients may develop short bowel syndrome that requires long-term parenteral nutrition, or may be a candidate for bowel transplantation.
Omphalocele
Definition
An omphalocele is characterized by an anterior abdominal wall defect at the base of the umbilical cord with herniation of intraabdominal contents within sac made of the layers of the umbilical cord—the amnion, Wharton jelly, and peritoneum.
Incidence
The incidence of omphalocele in fetuses at 12 to 16 weeks’ gestation is approximately 1:1100 as determined by ultrasound examination and approximately 1:4000 live births.
There is a significant fetal loss due to lethal anomalies as well as termination of pregnancy.
Pathophysiology
In the 6th week of normal embryonic development the midgut herniates into the coelom in the umbilical cord, then returning to the abdominal cavity in the 10th week.
An omphalocele is persistent herniation of the midgut likely resulting from failure to complete migration and fusion of the lateral embryonic folds and abdominal wall closure at the umbilical ring.
Genetics
Chromosomal abnormalities occur in 29% to 49% of patients with omphalocele.
Chromosomal abnormalities include trisomies 13, 14, 15, 16, 18, and 21, and triploidy.
An omphalocele that contains extracorporeal liver often has a normal karyotype.
Chromosomal anomalies are more frequent when the patient has additional anomalies, such as cardiac defects.
Risk factors
In utero exposure to SSRIs has been suggested to be associated with the development of an omphalocele. However, SSRIs have not been demonstrated to significantly increase the overall risk of congenital malformations.
Otherwise, there are no specific risk factors for an omphalocele.
Clinical presentation
The vast majority of omphaloceles are diagnosed prenatally.
Maternal serum α-fetoprotein levels may be elevated (less than gastroschisis), which triggers a level 3 ultrasound evaluation.
Structural anomalies, seen on prenatal ultrasound, occur in up to 80% of omphaloceles.
Termination of pregnancy is performed in 30% to 50% of cases.
Omphalocele is associated with nonchromosomal anomalies (30%) including Beckwith-Wiedemann syndrome, Turner syndrome, Goltz syndrome, Marshall-Smith syndrome, Meckel-Gruber syndrome, Otopalatodigital type II syndrome, CHARGE syndrome, and fetal valproate syndrome; malformation complexes including pentalogy of Cantrell; malformation sequences including ectopia cordis, bladder exstrophy, cloaca exstrophy, and OEIS (omphalocele, exstrophy of bladder, imperforate anus, spinal defect).
Diagnosis
Prenatal diagnosis
Prenatal ultrasound can diagnose omphalocele 95% of the time.
A nonliver-containing omphalocele may be diagnosed after 12 weeks’ gestation. A liver-containing omphalocele may be diagnosed earlier than 12 weeks because herniated liver is not a normal developmental finding.
When an omphalocele is identified on second trimester ultrasonography, maternal serum α-fetoprotein concentration will be elevated 70% of the time. Amniotic fluid α-fetoprotein concentration is also typically elevated.
Once omphalocele is identified on ultrasonography it should be further evaluated by fetal chromosomal analysis, testing for Beckwith-Wiedemann syndrome, amniotic fluid α-fetoprotein testing, and a fetal echocardiogram.
A discussion with the prospective parents is necessary as the prognosis may be grim in fetuses with multiple anomalies and chromosomal abnormalities, and termination of pregnancy may be their preference. Data from a European review noted that the request for termination in cases of omphalocele were as high as 83%.
Management
Perinatal care
Fetuses with an omphalocele should generally be allowed to come to full term and preferably deliver via vaginal route. In cases where there is a giant defect and a majority of the liver is out of the abdomen, the OB may prefer a cesarean section to avoid liver injury; however, vaginal delivery has not been shown to cause increased complications.
It is imperative to look for additional anomalies on fetal ultrasound especially cardiac, as has been mentioned. There are no specific markers of concern that have been reported for omphalocele that would trigger an early delivery.
As mentioned, a discussion regarding termination in these cases is quite frequent.
Neonatal medical management
As opposed to gastroschisis, in cases of an intact amnion sac with an omphalocele no urgent intervention is required.
The sac should be kept moist with a saline soaked gauze, or a petrolatum-laden gauze to prevent desiccation.
Urgent cardiac echocardiography may be required, and certainly is needed prior to any operative intervention.
A karyotype should be sent if not done prenatally.
A search for additional anomalies including the GU tract should be performed. Omphalocele defects may be in the epigastrium where they are associated with the pentalogy of Cantrell, or they may be in the suprapubic region and associated with a cloacal exstrophy, which is usually evident.
A special consideration is that of a prenatally ruptured omphalocele (Figure 34-3)—these are distinguished from gastroschisis by the presence of liver in the defect. These are very challenging to manage due to the viscera that are out and lack of abdominal domain.
Prolonged ventilation may be required due to pulmonary hypoplasia, and a tracheostomy is occasionally required.
Neonatal surgical management
After appropriate neonatal resuscitation has been performed and echocardiography to rule out cardiac anomalies, the defect is assessed and a decision regarding the surgical repair is made. There are a number of options available, and the approach is not as standardized as noted in gastroschisis.
For the defects that are very large, or have major cardiac issues, nonoperative management with topical application of agents that lead the sac to form an eschar epithelialize are used. These combined with judicious wrapping of the sac can result in a remarkable reduction in the size of the defect, but most will still have a large ventral hernia that is cared for after a few years of life.
Immediate repair has been performed for moderate to large sized defects as well. This may require the use of a prosthetic mesh closure in some cases, and may need a staged approach with gradual reduction of contents and creation of abdominal domain. Care has to be exercised not be excessively vigorous with the reduction as increased intraabdominal pressure may lead to abdominal compartment syndrome.
For smaller defects, a primary closure is preferable and is usually performed when the neonate is stable.
Postoperative care
Patients who undergo repair in the neonatal period must be monitored carefully for the presence of abdominal compartment syndrome in which there will be difficulty ventilating the baby, diminished urine output, and possibly decreased venous return from the lower part of the body. In that case, the pressure must be released by loosening the repair.
Care must also be exercised to not fluid resuscitate the neonate too aggressively, as edema may lead to increased abdominal pressure.
Once bowel function has resumed, as noted by bowel movements as well as decreased nasogastric tube output, feeding can be started.
The period of bowel rest is less than that noted in gastroschisis, as the intestines have not been exposed to amniotic fluid.
Early developmental/therapeutic interventions
Again, nonnutritive feeding skills should be addressed early.
As with gastroschisis, it is important to resume or start feedings as soon as possible, and breast milk would be the preferred choice.
Further interventions in cases of omphalocele depend on the presence of associated anomalies or defects as well as chromosomal issues. Early involvement of a geneticist may be required in some cases and the parents must be involved in the understanding of the condition and the long-term issues associated with them.
Prognosis
Prognosis for omphalocele is not as favorable compared to gastroschisis.
There is already a significant hidden mortality for this condition through fetal loss via demise or termination, and for the live born neonates survival is very closely linked to the presence of associated anomalies.
In one review it was noted that the survival of a fetus with omphalocele was between 23% and 52%.
Beyond survival, there are significant morbidities with giant omphalocele patients—pulmonary hypoplasia and chronic lung problems are noted, with some requiring a tracheostomy. GER and oral feeding problems are quite frequent; however, this may tend to resolve with time.
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