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A newborn male infant is born to a 21 year old G2P1 mother at 36 weeks gestation via cesarean section. Appropriate antenatal care and monitoring occurred throughout the pregnancy. Prenatal ultrasonography was done at 32 weeks gestation revealing what appeared to be free intestine floating in the amniotic fluid, coming from the anterior abdominal wall. The mother elected for a cesarean section delivery after fetal lung maturation was assured (at 36 week gestation in this case scenario). The baby looks normal at birth except for matted intestinal loops coming through an anterior abdominal wall defect just to the right of the umbilical cord. The loops are very edematous and do not resemble normal intestines. Treatment in the delivery room includes evaluation of the ABCs, then the intestines are wrapped with saline soaked sterile gauze (well padded with no pressure), followed by dry sterile dressings to minimize heat loss. Placement of a nasogastric tube to decompress the stomach and warming for maintenance of a normal temperature are done next. No attempt is made to force the exteriorized intestines back into the abdominal cavity. The patient is transported to NICU where the neonatologists first take care of his medical needs, and a pediatric surgeon is consulted.
Omphalocele (OC) and gastroschisis (GS) are congenital defects of the anterior abdominal wall. They are usually associated with gut abnormalities, including abnormal rotation and fixation. Although the midgut is usually nonrotated, complications secondary to this including volvulus are infrequent, and duodenal obstruction from Ladd's bands is rare. Both these conditions (OC and GS) are obvious at birth.
An omphalocele arises at the umbilical ring as a central defect secondary to developmental arrest of layers of the abdominal wall. Embryologically different, a gastroschisis involves the base of the umbilical stalk, with the defect in the abdominal wall always occurring lateral to the base of the umbilicus, through which a portion of the intestine has escaped (usually the right side). Originally confused as a type of omphalocele, gastroschisis is now recognized as a separate entity. This defect may represent an isolated congenital defect in the abdominal wall, or be the result of closure of the celomic cavity while a portion of the intestinal tract remained trapped outside the abdomen, at the base of the umbilical cord. The intestines float freely in the amniotic fluid.
The diagnosis of both types of anterior abdominal wall defects are frequently made antenatally by ultrasound, as early as 12 weeks gestation. Diagnosis is made entirely by inspection and is readily apparent after delivery. Striking differences between the two are obvious. An omphalocele is usually covered by a translucent membrane overlying the bowel and solid viscera. Size varies from a small hernia of the cord (1 to 2 cm in diameter), to a huge mass containing essentially all the abdominal viscera. Usually, the sac remains intact, but it occasionally ruptures during delivery. The defect is always within the umbilical ring. The sac may contain bowel, stomach, and liver. Omphaloceles are often associated with other congenital malformations and with abnormal karyotypes. Occasionally, the bowel is attached to the sac.
Alternatively, the defect of gastroschisis is lateral to the umbilicus. This has allowed the escape of the intestine into the amniotic cavity at different times in fetal development. Therefore, the appearance of the intestines are variable. Some appear edematous and matted that have been exposed to the amniotic fluid for many weeks, while other intestines are glistening and normal looking, as they "escaped" just before birth. There is no sac, and the liver does not protrude.
The immediate treatment in the delivery room is similar for both conditions. The abdomen (omphalocele) or exteriorized intestine (gastroschisis) is wrapped with saline soaked sterile gauze (well padded with no pressure), followed by dry sterile dressings to minimize heat loss. Placement of a nasogastric tube to decompress the stomach and maintenance of a normal temperature are essential. No pressure is placed on the omphalocele and there should be no attempt to reduce it. This maneuver may rupture the sac, interfere with venous return, and/or impede the infant's respiratory effort. Similarly, no attempt should be made to force the exteriorized gastroschisis intestine back into the abdominal cavity.
Although the definite treatment is surgical, delay in closure has no adverse outcome. Therefore, it is essential that optimal resuscitation occur prior to surgery. The general consensus on operative management of abdominal wall defect is to provide primary closure, if it can be achieved without hemodynamic or respiratory compromise. Patients with primary closure have better survival rates, reduced risk of sepsis and overall, a shorter hospital stay.
Although smaller omphaloceles usually undergo primary closure, giant omphalocele in the neonate is a challenging surgical emergency that requires individualized approaches to operative repair. In general, omphaloceles greater than 6 cm in diameter require silo reduction with silastic interwoven with Marlex. A silo is first created, by placing the intestines into what looks like a plastic bag turned upside down, with the edges of the bag sewn to the edges of the opening in the abdomen. This essentially creates an "artificial abdomen". The contents of the bag are squeezed daily from the top down, slowly forcing the intestines back into the abdomen. Over days to weeks the intestines are pushed back into the abdomen, and the abdominal wall is finally closed.
Interesting methods have recently been described utilizing continuous controlled pressure to achieve smooth, rapid, and safe silo reduction of an anterior abdominal wall defect. One example includes a metal tube with larger wheels at each end that is suspended by runners and counterweights, to slowly roll the silo and squeeze the contents into the abdominal cavity.
More recently a silastic spring-loaded silo (SLS) has been used routinely (in one center) for infants with gastroschisis. These surgeons found that SLS, followed by elective repair, permitted gentle, gradual reduction in the viscera. SLS was associated with lower airway pressures, earlier extubation, fewer complications, and decreased length of stay and hospital charges.
Regardless of the methods, the principles of the silo technique rely on steady pressure on the prosthesis, and a reduction in size over several days, to bring about gradual reduction of the intestines. Finally, once reduced, surgical closure can be accomplished. Irrigation with povidone-iodine (Betadine) solution or coverage with a layer of silver sulfadiazine cream (Silvadene) is effective in reducing surface contamination throughout the time for which the prosthesis is required.
Although the survival rate of patients with abdominal wall defects has gradually improved with the advances in the diagnostic and treatment modalities, the outcome is largely dependent on coexisting anomalies. Omphaloceles are often associated with abnormal karyotypes (trisomy 13, 18, and 21) or congenital malformations. In a recent review, 10 of 31 cases of omphalocele (OC) and 4 of 11 cases of gastroschisis (GS) cases, multiple congenital anomalies were diagnosed. The birth weight was below the 10th percentile in 23% of OC and 36% of GS cases. An abnormal prenatal karyotype was established in 5 of 25 OC cases versus none in the GS group. In 36 cases, an expectant obstetric management was followed, and in six OC cases, the pregnancies were terminated because of severe multiple anomalies (3 cases) or an abnormal prenatal karyotype (3 cases). The preterm delivery rate (excluding terminations) was 12 of 25 in the OC group versus 8 of 11 in the GS group. The cesarean section rate was almost identical (19% versus 18%) in both subgroups, the majority of which were performed to protect the abdominal wall defect. The overall survival rate was 39 per cent in the OC group compared to 72% in the GS group.
The surgeon must be aware of other associated defects. Congenital malrotation of the colon usually occurs in patients born with an omphalocele. Although not a serious defect, the anomaly can lead to midgut volvulus and intestinal obstruction in a baby who has previously recovered from treatment of an omphalocele, and therefore must be corrected at the time of initial surgery.
A different defect, intestinal atresia, occurs in about 10% of patients with GS. In these infants, the clinical course is one of early complete obstruction, which requires abdominal exploration if the lesion has been inadvertently overlooked at the time of initial repair of the gastroschisis. Rarely, there is a short gut from an antenatal volvulus.
Even after successful reduction of the bowel and closure of the defect, normal motor function of the gut may be delayed for weeks to months in cases of gastroschisis. Although long term outcome of these patients is generally good, they have high incidence of gastroesophageal reflux (GER) (40-50%) for which they should be closely monitored. Parenteral nutrition and intensive care have markedly improved survival.
A recent follow-up study was done involving patients post-operatively, from 1-28 years prior. Primary closure was possible in 25 omphalocele (OC) and 20 gastroschisis (GS). Eighteen children with OC and 8 with GS suffered from additional abnormalities, which were treated simultaneously. Twenty percent of the babies with OC died mostly because of severe congenital anomalies and 12.9% of GS because of infectious complications in combination with other diseases. There were fewer neonatal deaths in the last decade, attributed to better operative and perioperative treatment, as well as abortions following improved ultrasound diagnosis (as early as 12 weeks gestation).
Long-term follow-up revealed normal growth and development, except for those with severe congenital anomalies. Late surgical problems have also recently been studied. A questionnaire concerning late surgical problems was distributed to the parents of 47 surviving children. The mean follow up time was 5.4 years. There was no mention of remaining problems regarding 16 of the 28 omphalocele patients and 10 of the 16 gastroschisis patients. Postoperative abdominal wall hernia was reported in 7 OC cases and in 6 GS cases. Postoperative intestinal obstruction occurred in 4 OC cases and 1 GS case. The other complications were related to abdominal pain, cryptorchidism, constipation and difficulties with care of the intestinal stoma. All the remaining problems could be corrected and the long-term results in both conditions were good.
In summary, an omphalocele or gastroschisis are congenital defects of the anterior abdominal wall. An omphalocele arises within the umbilical ring as a central defect, while a gastroschisis involves the base of the umbilical stalk, with the defect in the abdominal wall always occurring lateral to the umbilicus. Although the diagnosis of both types are frequently made antenatally by ultrasound, if missed, they are readily apparent after delivery in the delivery room, where striking differences between the two are obvious. Although the survival rate of patients with abdominal wall defects has gradually improved, the outcome is largely dependent on coexisting anomalies. Although surviving children without severe congenital anomalies have a good quality of life, late surgical problems are seen, and close follow-up is essential to good outcome.
1. The earliest way to diagnose an anterior abdominal wall defect is:
. . . . . a. by physical exam
. . . . . b. by history
. . . . . c. by fetal ultrasound
. . . . . d. by fetal CT scan
2. The following are correct regarding omphaloceles except:
. . . . . a. is usually covered by a translucent membrane
. . . . . b. is frequently associated with other congenital malformations
. . . . . c. is lateral to the umbilical stump
. . . . . d. is within the umbilical ring
3. The following are true about gastroschisis:
. . . . . a. occurs lateral to the umbilical stump
. . . . . b. can be diagnosed antenatally
. . . . . c. at birth often have edematous matted intestinal loops
. . . . . d. all of the above
4. Treatment of abdominal wall defects includes:
. . . . . a. immediate surgical repair
. . . . . b. pushing the intestines back into the abdominal cavity while still in the delivery room
. . . . . c. provide immediate optimal resuscitation and stabilization first, and then surgery
. . . . . d. always do primary closure in both lesions
5. The true statement below is:
. . . . . a. The surgeon does not need to worry about other associated defects as the neonatologist will already have treated them.
. . . . . b. There are essentially no late surgical problems after repair.
. . . . . c. Improved ultrasound diagnosis has resulted in some women seeking termination of pregnancy as early as 12 weeks gestation.
. . . . . d. The long term outcome of survivors reveal poor growth and development.
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