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Abdominal Wall Defects abdominal cavity

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Abdominal Wall Defects abdominal cavity

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									Abdominal Wall Defects
The first description of an abdominal wall defect is credited to    with subsequent resorption of the remnants of the sac. The fact
Pare in 1634. Visick was the first to treat an infant with a        that serious associated anomalies are rare-and trisomy
ruptured omphalocele successfully with a skin closure in 1873.      syndromes, Beckwith-Wiedemann syndrome, and exstrophy of
The skin flap method of closure developed by Gross in Boston        the bladder and cloaca are never seen with gastroschisis-
in 1948 was an important advance in the surgical management         strongly suggests that these two anomalies are different.
of infants with omphalocele and improved the outcome for            Studies concerning serial sections of human fetuses in the
neonates with gastroschisis. Lack of availability of infant         Carnegie Embryologic Collection seem to confirm the
ventilators and inability to maintain adequate nutrition during     impression that gastroschisis and omphalocele are different
the prolonged adynamic ileus that accompanies gastroschisis         conditions. A more in-depth examination of the embryology is
played a role in the poor outlook for these infants before the      beyond the scope of this chapter, which reviews some of the
1960s.                                                              similarities and differences between gastroschisis and
   In 1965, Dudrick and associates described their experience       omphalocele (Table 40-1) and describes the current diagnostic
with total parenteral nutrition (TPN) in the laboratory and         and therapeutic management of infants with these congenital
clinical setting. At the same time, the first infant pressure       abdominal wall malformations.
ventilators and then volume ventilators became available for
clinical use in neonates. In 1967, Schuster reported the
successful application of a temporary extra-abdominal housing
for the bowel in instances of large omphaloceles using an inner
lining of polyethylene sheeting and an outer layer of
polytetrafluoroethylene (Teflon) mesh. This technique also was
applied to infants with gastroschisis and was modified by
others, including Allen and Wrenn, using Dacron-reinforced
Silastic, an alternative prosthetic material. Their silo method
was a simpler technique and promptly was adopted by most
pediatric surgeons. These three events in the 1960s
significantly changed the outcome for infants with abdominal
wall defects. Since then, recognition of abdominal wall defects
in utero by prenatal ultrasonography, improved understanding
of associated chromosomal abnormalities in infants with
omphalocele, continued advances in neonatal intensive care by
development of
more effective infant ventilators, and significant improvements
in monitoring in the neonatal intensive care unit (NICU) and
operating room have influenced further the overall
management of these patients.
   There is some controversy regarding the exact embryologic
basis of abdominal wall defects and whether gastroschisis and
omphalocele are distinctly separate entities. Based on
embryologic and prenatal ultrasound studies, some authors
suggest that gastroschisis is the result of an early intrauterine
rupture of the umbilical cord or an early intrauterine rupture of
an omphalocele
424       CHAPTER 40          Abdominal Wall Defects


 GASTROSCHISIS
 Gastroschisis (Greek for "belly cleft") is a defect of the
 anterior abdominal wall just lateral to the umbilicus. The
 defect is almost always to the right of an intact umbilical
 cord and in some cases is separated from the cord by an
 intact skin bridge. This anomaly is probably the result of a
 defect that occurs at the site where the second umbilical
 vein involutes. In contrast to instances of omphalocele,
 there is no peritoneal sac so that antenatal evisceration of
 the bowel occurs through a relatively small defect during
 intrauterine life. The irritating effects of amniotic fluid (pH
 7.0), which contains fetal urine and various growth factors,
 on the exposed bowel wall results in a chemical form of
 peritonitis characterized by a thick edematous membrane
 that is occasionally exudative. The exposed viscera may be
 congested, and the bowel appears matted and
 foreshortened (Fig. 40-1). There is a varying degree of               FIGURE 40-2 III Bowel compressed in a tight gastroschisis defect,
                                                                       resulting in bowel atresia.
 mesenteric venous and lymphatic obstruction resulting
 from the small abdominal wall defect. Nonrotation always
 accompanies this condition, and the bowel is not fixed to
                                                                    40% are either premature or small for gestational age.
 the abdominal wall. In contrast to infants with
                                                                    Gastroschisis is more common than omphalocele, with a ratio
 omphalocele, the incidence of associated anomalies in
                                                                    of 1.5:1 to 2:1 at most major pediatric surgical centers.
 patients with gastroschisis is relatively infrequent. The
                                                                    Occasionally there is a maternal history of a previous infant
 exception is the occurrence of intestinal atresia, which may
                                                                    with gastroschisis. Chromosomal syndromes almost never are
 complicate gastroschisis in 10% to 15% of patients.
                                                                    encountered in infants with a gastroschisis defect.
 Atresia of the bowel often is related to intrauterine volvu-
                                                                        Gastroschisis frequently can be detected on a prenatal
 lus, intussusception, or an interruption of the blood supply
                                                                    ultrasound study. The sonogram often shows dilated bowel free
 to a segment of exposed intestine by compression in a tight
                                                                    in amniotic fluid adjacent to the umbilical insertion (Fig. 40-3).
 defect in the abdominal wall (Fig. 40-2). The liver is
                                                                    When identified prenatally, the pregnant woman should be
 almost never eviscerated; the stomach, small bowel, and
                                                                    referred to a high-risk obstetric unit with an NICU and
 large intestine usually reside outside the defect. The bowel
                                                                    pediatric surgical expertise. Although an elective preterm
 may be perforated in approximately 5% of patients.
                                                                    delivery theoretically may minimize the irritating effect of
 Occasionally the ovaries and fallopian tubes in girls and an
                                                                    amniotic fluid exposure, evidence does not suggest that early
 undescended testis in boys are found outside the defect.
                                                                    cesarean section improves the outcome. Spontaneous vaginal
 The abdominal cavity is often small. The sexes are equally
                                                                    delivery is a reasonable choice for most of these infants, unless
 affected. Most patients are born to young mothers; 25%
                                                                    the eviscerated intestine appears unusually large.
 are born to teenaged mothers. Of patients,                             When delivered, infants with gastroschisis may experience
                                                                    various problems as a result of an increase in insensible fluid
                                                                    and heat losses related to exposure of the eviscerated bowel.
                                                                    Hypothermia, hypovolemia, and sepsis are the major problems
                                                                    to avoid. Significant third-space fluid deficits and
                                                                    hypoproteinemia occur as the result of extra-abdominal and
                                                                    intra-abdominal sequestration of interstitial fluid. The lower
                                                                    half of the infant (including the eviscerated bowel) is placed
                                                                    into a sterile bowel bag, feet first, up to the level of the axillae
                                                                    (Fig. 40-4). This plastic bag is available in almost every
                                                                    operating room and helps retain the infant's heat, reduces
                                                                    evaporative insensible losses, reduces the risk of sepsis, and
                                                                    collects sequestered fluids that can be measured and replaced
                                                                    accurately.
                                                                        Fluid requirements in a neonate with gastroschisis are two
                                                                    to three times that of a normal newborn in the first 24 hours of
                                                                    life. In a large group of infants with gastroschisis, the average
                                                                    fluid requirement was approximately 175 mLlkg/day. As a
      FIGURE 40-1 III Typical gastroschisis defect just to the      general rule, the more matted and inflamed the exposed viscera
      right of an intact umbilical cord. The eviscerated bowel is   appear, the greater the fluid requirements necessary to
      matted, edematous, and foreshortened. No sac is observed.     resuscitate the infant. The infant is resuscitated with a bolus of
      (From GrosfeldJL, et al: Congenital abdominal wall defects:   20 mLlkg
      current management and survival. Surg Clin North Am
      61:1037,1981.)
                                                            PART VI Abdominal Wall, Peritoneum, and Diaphragm               425




A
                                                                          FIGURE 40-4 Newborn infant with an abdominal wall defect placed
                                                                          feet first in a bowel bag.

                                                                          has adynamic ileus. The infant is given parenteral antibiotics in
                                                                          divided doses (ampicillin, 50 to 100 mglkg/day, and
                                                                          gentamicin,S to 7 mglkg/day in 3 doses). When the acidosis is
                                                                          corrected and urine output is established, the infant is taken to
                                                                          the operating room for repair. With the infant under well-
                                                                          monitored general endotracheal anesthesia, the abdominal wall
                                                                          and exposed viscera are cleansed carefully ofloose debris with
                                                                          warm sterile saline and prepared with an iodophor solution.
                                                                          Alcohol or alcohol-containing solutions should not be applied
                                                                          directly on the bowel because they have an irritating effect. The
B                                                                         bowel is inspected carefully for accompanying atresia or perfora-
                                                                          tion. The umbilical cord is inspected and the number of
                                                                          umbilical arteries noted. The abdominal wall defect is enlarged 1
FIGURE 40-3 Gastroschisis. A, Obstetric sonogram at 34 weeks'             to 2 cm cephalad and caudad to improve the mechanical
gestation shows dilated bowel (arrows) free in amniotic fluid             advantage for reducing the exposed viscera (Fig. 40-5). The
adjacent to the umbilical cord insertion site. Previous sonograms at
                                                                          stomach, duodenal, and upper jejunal
27 and 31 weeks showed the bowel contained near the base of the
cord, suggesting rupture of a small omphalocele (hernia of the
cord) late in gestation. B, Typical gastroschisis after delivery at 35
weeks. Bowel edema and inflammation are minimal.



of 10% dextrose in lactated Ringer's solution given over 30
minutes. Additional fluids (additional bolus of 10 mLlkg of
human plasma protein fraction [PlasmanateJ and lactated
Ringer's solution at a rate of 150 to 200 mL/kg/day divided
into hourly aliquots) are administered until urine output is
established, and the pulse rate and tissue perfusion improve.
Although most patients require rigorous fluid resuscitation,
there are two subsets: a "low group" and a "high group." The
low group is usually premature, is physiologically stable,
and requires only 90 to 125 mLlkgl 24 hours for
maintenance. The high group is often small for gestational
age, has elevated hematocrit levels, and requires 190
mLlkg/24 hours (see Chapter 4). Acid-base balance is
monitored closely because metabolic acidosis commonly is
observed as a result of poor perfusion related to
                                                                                      FIGURE 40-5 The small abdominal defect is opened 1 to 2
hypovolemia.                                                                          cm cephalad and caudad to improve the mechanical
An orogastric tube is placed into the stomach to remove                               advantage when attempting reduction of the herniated
swallowed air and to aspirate gastrointestinal contents                               viscera. The abdominal cavity is stretched manually in an
because the infant with gastroschisis almost invariably                               attempt to increase the right of domain for the bowel.
  426      CHAPTER 40 Abdominal Wall Defects



contents are aspirated through the previously placed orogastric     usually can be removed and closure of the abdominal wall
tube, and meconium in the transverse, descending, and sigmoid       completed within 1 to 3 weeks in most cases. The infant is
colon and rectum is evacuated manually through the anal             returned to the operating room for fascial closure using interrupted
orifice by external compression of the viscera. An enterotomy       full-thickness 3-0 or 2-0 nonabsorbable monofilament sutures.
to decompress the bowel is unnecessary and should be avoided        Parenteral antibiotics are discontinued shortly after the silo is
because it may result in a leak with subsequent peritonitis or an   removed.
enterocutaneous fistula. Similarly, if an asymptomatic Meckel's         As a result of prolonged adynamic ileus, almost all infants with
diverticulum is present, it should be left in place and not         gastroschisis require TPN for adequate caloric support. A central
excised. The abdominal wall is stretched manually to enlarge        venous catheter is inserted at the time of abdominal closure. TPN
the relatively small peritoneal cavity (see Fig. 40-5).             is started when the fluid derangements observed at birth are
    Primary reduction of the viscera is attempted using a           corrected (24 to 48 hours later) and may be required for 3 to 4
maximum ventilatory pressure of 35 cm H 0 as a safe reference       weeks. The solution contains 25% glucose, 2.5% amino acids, and
guide; this is successful in more ilian 50% of patients. Inferior   3 to 4 g/kg/day of fat using 10% or 20% Intralipid, trace minerals,
vena caval and intragastric pressure measurements occasionally      and vitamins. The infants should receive 125 to 130
have been used to monitor the ability to perform a primary          calories/kg/day. Most infants begin to tolerate oral intake by 2 to 3
closure of the abdominal wall safely. When there is                 weeks of age and usually can take all of their calories enterally by
considerable visceroabdominal disproportion, attempts to close      1 month. Dilute lJ4-strength to liz-strength formula is given
the abdomen primarily under moderate tension increase the risk      initially, and the volume is increased slowly, depending on the
of bowel perforation or leak. The abdominal wall closure is         volume of gastric residuals. In the first few weeks of life, patients
accomplished using one layer of full-thickness interrupted 3-0      with gastroschisis have decreased absorption of carbohydrates,
nonabsorbable polypropylene sutures that do not include the         protein, and fat; however, absorptive function returns to normal
skin. Often the umbilicus can be preserved for cosmetic             for all three caloric sources by 6 months of age.
purposes. Several surgeons create an umbilicus with a purse-            In infants with associated intestinal atresia, a temporary
string suture during skin closure.                                  enterostomy occasionally is constructed at the time of the initial
    After primary closure, most infants are maintained on           abdominal wall repair. Closure can be accomplished within 1 to 3
ventilator support for 24 to 48 hours and are weaned and            months. Primary anastomosis can be performed in the neonatal
extubated safely in the NICU. Although previously surgeons          period after abdominal closure in most patients within 1 to 2
often performed an adjunctive gastrostomy in infants with           weeks as an elective procedure when the intestinal edema and
abdominal wall defects, this has been found to be unnecessary       inflammation have largely subsided, and the gastric, biliary, and
in most cases, and it may interfere with abdominal closure and      pancreatic drainage is controlled with an orogastric suction
cause a higher complication rate. An orogastric tube is tolerated   catheter. Anastomosis at birth often is complicated by stricture or
well by infants and does not interfere with nasal breathing.        leak in many patients. Patients with atresia often have longer
    Primary abdominal repair may not be possible in 40% to          delays in recovery of gastrointestinal function and a more
50% of reported cases of gastroschisis. Too tight a closure may     complicated and prolonged hospitalization. In some instances, the
result in cardiorespiratory compromise from diaphragmatic           entire midgut may be involved by ischemia as a result of being
elevation and ventilatory restriction, vena caval compression       trapped in a small defect in utero or by a volvulus resulting in
that reduces venous return to the right side of the heart, and      short bowel syndrome. The only remaining bowel may be atretic
compression of the bowel mesentery, resulting in diminished         and significantly thickened, inflamed, and dilated with abnormal
bowel perfusion and intestinal ischemia and necrosis. Some          intestinal motility. After a temporary enterostomy is fashioned in
infants require a staged closure using a Dacron-reinforced          the neonatal period to allow time for the thickened and inflamed
Silastic silo as a temporary extra-abdominal housing. The edge      bowel wall to return
of the prosthetic material is sutured to the rim of the fascia or   to near normal, a tapering enteroplasty and bowel anastomosis
skin at the edge of the defect with continuous or interrupted 3-0   subsequently can be performed. Occasionally a Bianchi procedure,
or 2-0 nonabsorbable monofilament sutures. The walls of the         which longitudinally divides the dilated intestine into two
prosthetic silo should be constructed parallel to each other as a   independent segments and increases its length, may be considered.
straight-walled structure so that the base is as wide as the top,   Intestinal atresia complicating gastroschisis may require long-term
preventing a conical narrow entry to the abdominal cavity (Fig.     TPN support and innovative enteral feeding programs best carried
40-6). The upper end of the silo is ligated with umbilical tape,    out with small hourly drip feedings maximally to stimulate
which is suspended loosely from the top of the infant's Isolette    adaptation and villus hyperplasia. Enteral feedings also maximize
unit. An antibiotic ointment (povidone-iodine [Betadine] ) is       gallbladder contraction and reduce the risk of TPN-related
placed around the base of the silo at the skin-prosthesis           cholestasis and the formation of pigment gallstones.
interface. A sterile support dressing is applied to prevent the         In addition to prolonged adynamic ileus, other postoperative
silo from tilting over and kinking the contained viscera. The       complications after repair of a gastroschisis defect include sepsis,
viscera can be reduced gradually by gentle pressure and placing     aspiration pneumonia, abdominal wall cellulitis, temporary groin
the ligature on the silo lower starting on the second to third      and lower extremity edema,
postoperative day using sterile technique at the bedside in the
NICU. The silo
                                                  PART VI Abdominal Wall, Peritoneum, and Diaphragm                    427




                                                                              .
                                                                 FIGURE 40-& A, An infant with gastroschisis and
                                                                 antenatal evisceration of the bowel. B, The intestine
                                                                 could not be completely reduced and was placed in a
                                                                 temporary Dacronreinforced Silastic "silo." C, The
                                                                 viscera is reduced gradually in the NICU with repeated
                                                                 gentle downward pressure on the upper end of the silo.
                                                                 The infant is returned to the operating room, the bowel is
                                                                 completely reduced, and a primary abdominal wall
                                                                 closure is performed.




necrotizing enterocolitis, and TPN-related cholestasis.
Symptomatic gastroesophageal reflux and inguinal hernia             Most deaths are related to prematurity or sepsis or late
may occur from increased intra-abdominal pressure as a result       complications occurring in infants with atresias and short-
of replacement of the herniated viscera in a relatively small       bowel syndrome, including progressive liver disease
abdominal cavity. Few patients require an antireflux                related to TPN. Most surviving patients have normal
procedure, however. Rarely the patient with gastroschisis           growth and development, tolerate a full diet, and have
remains obstructed for more than 4 to 5 weeks as the result of      normal bowel habits.
severe visceroabdominal disproportion with intestinal edema
and matting, a missed second atresia, or distal intraluminal        OMPHALOCELE
web that was masked by the inflammatory process present at          An omphalocele is a covered defect of the umbilical ring
the initial procedure. Patients with a prolonged obstructive        into which abdominal contents herniate. The defect is
course should undergo radiographic intestinal contrast studies      related to a central defect of the umbilical ring and the
in an attempt to locate a mechanical cause of obstruction.          medial segments of the lateral embryonic abdominal wall
With appropriate neonatal resuscitation, surgical treatment,        folds. This defect is thought to occur in the third week of
and nutritional support, the current survival rate in infants       intrauterine life when the midgut elongates and resides in
with gastroschisis is greater than 90%.                             the yolk sac outside of the embryonic coelom. This is
                                                                    referred to as the middle celosomia or a central
                                                                    omphalocele.
428     CHAPTER 40 Abdominal Wall Defects



 Omphaloceles are covered by a sac composed of an outer layer
 of amnion and an inner layer of peritoneum. The umbilical cord
 inserts into the sac. A separate compartment containing
 Wharton's jelly also may be observed. The omphalocele defect
 may reside in an epigastric location as a result of a defective
 cephalad abdominal wall fold development, usually in
 association with many other defects involving the diaphragm,
 sternum, and heart. An omphalocele defect also may reside in
 the hypogastrium as a result of defective development of the
 caudal abdominal wall fold and coexist with other defects
 affecting the genitourinary system, the primitive hindgut, and
 the caudal neural tube.
     The incidence of omphalocele is approximately 1 in 5000
 live births. Boys are affected more often than girls. Infants with
 an omphalocele have a high incidence of associated anomalies.
 More than 50% of cases have other serious defects involving
 the alimentary tract and the cardiovascular, genitourinary,
 musculoskeletal, and central nervous systems. Many infants
 born with an omphalocele are premature. Others may be
 affected by many chromosomal syndromes, including
 Beckwith-Wiedemann syndrome characterized by gigantism,
 macroglossia, and an umbilical defect in the form of either an         FIGURE 40-7 Lower midline ompha1ocele with exstrophy of the cloaca
 umbilical hernia or an omphalocele. Infants with Beckwith-             and imperforate anus with colon atresia. The halves of the bladder are
 Wiedemann syndrome have visceromegaly and pancreatic islet             separated by a vesicointestinal fissure with prolapsing right colon.
 cell hyperplasia that may result in significant hypoglycemia
 complicated by seizures in the neonatal period. These infants
 also have an increased incidence of malignant tumors,                  abdominal cavity that may make attempts at reducing the sac
 including Wilms' tumor, neuroblastoma, and adrenocortical              contents extremely difficult. In addition, anomalies of rotation
 tumors. Omphalocele may occur in infants with other serious            and fixation almost always are present as a coexisting
 chromosomal abnormalities, such as trisomies 13 through 15,            anomaly. Meckel's diverticulum also is seen with increased
 trisomies 16 through 18, and trisomy 21.                               frequency in these patients.
     When the omphalocele is located in the hypogastrium, it            The diagnosis of omphalocele can be obtained by prenatal
 often is associated with a lower midline syndrome, which               ultrasound examination (Fig. 40-10). The early detection of
 includes exstrophy of the bladder or cloaca, vesicointestinal          this defect allows for maternal counseling,
 fissure, colon atresia, imperforate anus, sacral vertebral defects,
 and a lipomeningocele or meningomyelocele (Fig. 40-7).
 Duplications of the appendix and atretic colon commonly are
 observed. The genitalia are often ambiguous, with a highly
 limited phallus in boys, and sex assignment must be considered
 carefully at an early stage. An epigastric omphalocele may be
 part of
 Cantrell's pentalogy, which includes omphalocele, anterior
 diaphragmatic hernia, sternal cleft, a downward displaced
 heart, intracardiac defects (most commonly a ventricular septal
 defect), and occasionally a diverticulum of the left ventricle
 that may extend down into the abdominal portion of the sac
 (Fig. 40-8).
 An omphalocele defect may vary from 2 cm to greater than 10
 cm in diameter. The smaller the defect, the better the prognosis.
 Many smaller defects «4 cm) probably represent herniation of
 the umbilical cord-a minor form of the defect. These smaller
 defects probably occur in the 8th to 10th week of gestation as a
 result of failure of the umbilical ring to close. An umbilical
 cord hernia usually contains only small bowel. In contrast,           FIGURE 40-8 Example of a ruptured epigastric omphalocele with the
 although the true omphalocele sac also may contain bowel, fre-        liver and the entire gastrointestinal tract eviscerated. A congenital heart
 quently the liver (in 35% of patients) (Fig. 40-9), colon, and        defect, sternal cleft, and anterior diaphragmatic defect also were present.
 stomach may be present within the sac. The extraabdominal             (From Grosfeld JL: Congenital abdominal wall defects: Current
 location of the viscera in utero results in a small                   management and survival. Surg Clin North Am 61:1037,1981.)
                                                                      PART VI Abdominal Wall, Peritoneum, and Diaphragm                          429




          A                                                                          B
          FIGURE 40.9 . A, Large omphalocele sac containing the liver and the intestine. B, In contrast, this infant had a small hernia of the umbilical cord that
          contained a few loops of intestine.




                  .
FIGURE 40.10 A and B, Prenatal diagnosis
of omphalocele and ectopia cordis by ultrasound.
The drawings on the left illustrate the anatomic
relations seen in the sonograms. A, Transverse
scan in the plane illustrated in the drawing shows                                                       A
a large mass that extends beyond the anterior limit
of the thorax. The umbilical vein/ductus venosus
(UV /DV) complex joins the left portal vein
(LPV). A sonolucent structure (cursor) adjacent to
the UV /DV is investigated further in B. By
slowing the rate of transducer motion, the
sonolucent structure seen in A can be identified
definitely as the fetal heart (lIt) by characteristic
wall motion. P, placenta; Sp, spine; R, rib; Th,
thorax; L, liver. (From Harrison MR, Golbus MS,
Filly RA, et al: Management of the fetus with a
correctable       congenital      defect.    lAMA
246:774,1981.)




 optimal delivery planning, and referral of the affected mother
                                                                                         that have a high perinatal morbidity and mortality. If the liver is
 to a high-risk delivery center supported by a con.temporary
                                                                                         recognized outside the abdomen within the sac, the defect is
 NICU and pediatric surgical expertise. Prenatal ultrasound
                                                                                         usually large; the infant's prognosis also depends on the
 studies can help distinguish between lesions with a good
                                                                                         presence or absence of serious associated anomalies. If the
 prognosis, such as a small omphalocele or hernia of the
                                                                                         defect is large, the mother commonly requires a cesarean
 umbilical cord, and lesions with a more guarded outcome,
                                                                                         section. With the exception of a large omphalocele, cesarean
 including a large omphalocele in fetuses with multiple
                                                                                         delivery has little advantage over a vaginal delivery in the
 anomalies and related syndromes
                                                                                         management of most fetal
430    CHAPTER 40 Abdominal Wall Defects




 abdominal wall defects (Fig. 40-11). Elevated a-fetoprotein       presents in each patient. Small defects (2 cm) can be managed by
 levels have been observed in the amniotic fluid from amnio-       direct primary closure of the abdominal wall. Medium-sized
 centesis samples in some infants with an omphalocele, even        defects are managed by careful removal of the sac at its base
 in the absence of associated neural tube defects. Fetoscopy       with suture ligation of the umbilical vein, the two umbilical
 may allow for fetal blood sampling and detection of serious       arteries, and the urachus. The abdominal wall is stretched
 chromosomal abnormalities. This is particularly useful in         manually on both sides to enlarge the size of the relatively small
 women with advanced maternal age (35 to 45 years) in whom         abdominal cavity. The liver and then the bowel are reduced into
 the age-specific risk of the fetus having a trisomy is two to     the abdomen. Reduction of the liver must be done carefully to
 three times greater than in younger women.                        avoid torsion of the hepatic veins, portal vein inflow, and injury
    At birth, the emergency care of neonates with omphalocele      to the hepatic capsule, which may result in significant,
 includes the insertion of an orogastric tube to decompress the    potentially life-threatening hemorrhage that is difficult to
 stomach and prevent swallowed air from causing bowel              control. Primary closure of the abdominal wall is not advisable
 distention, which may interfere with attempted reduction of       for patients with large omphaloceles and visceroabdominal
 the viscera at the time of repair. The intact omphalocele sac     disproportion. If the abdominal wall fascia cannot be
 should be kept covered with a plastic sheet, protected from       approximated, skin closure with creation of a small ventral
 injury, and transported in a thermally neutral environment.       hernia may be used in some patients. If the skin flaps are not
 Wet dressings may macerate the sac, cause temperature loss        extensively undermined, the subsequent ventral hernia remains
 by cooling and evaporative loss, and adhere to the sac. If the    small and is easier to repair at a later date. Some surgeons prefer
 sac is large and unstable, causing collapse to one side or the    to bridge the defect by insertion of a prosthetic material, such as
 other, resulting in kinking of the enclosed viscera and even      Gore-Tex, Marlex, or absorbable patches.
 obstruction of the inferior vena cava, the sac should be              Primary abdominal wall repair is usually not possible for
 supported by a sterile gauze roller dressing (Kerlix) that        infants with large omphalocele defects. These infants often
 wraps around the infant's back. Intravenous fluids are            require a staged abdominal wall closure using a Dacron-
 administered using 10% dextrose in water and 0.25% normal         reinforced Silastic silo as a temporary extraabdominal locale for
 saline solution if the infant is hemodynamically stable. The      the bowel. This technique first was described by Schuster in
 fluid losses are usually not excessive because the viscera are    1967 and has had a positive impact on survival in these difficult
 covered by an intact sac.                                         cases. Similar to infants with gastroschisis, the prosthetic
    Approximately 10% of patients have a rupture of the            material is sutured to the skin at the edge of the abdominal wall
 omphalocele sac. In these instances, fluid losses are sig-        defect with a polypropylene or other nonabsorbable
 nificantly greater and similar to fluid losses of infants with    monofilament suture. The vessels in the umbilical cord are
 gastroschisis. These patients require more vigorous fluid         ligated, but the covering sac need not be excised before placing
 resuscitation using 20 mL/kg of 10% dextrose in lactated          the Silastic silo. The silo should be constructed with its walls
 Ringer's solution as a priming bolus given over 30 to 60          perpendicular to the abdominal wall and parallel to each other to
 minutes followed by an increased maintenance volume.              avoid a conical base and difficulty in attempted reduction of the
 Perioperative parenteral antibiotics are administered             herniated viscera. Iodophor or antibiotic ointment is placed
 (ampicillin, 50 to 100 mglkg/day, and gentamicin, 5 to 7          around the base of the sac on the skinprosthesis interface. The
 mg/kg/day in 3 doses). The infant's general condition should      contents of the sac are supported by umbilical tape suspended
 be assessed carefully in regard to cardiorespiratory status and   from the top of the Isolette and attached to the apex of the
 the possible occurrence of additional congenital anomalies.       prosthesis. The viscera can be reduced gradually over 3 to 10
     Because the viscera are covered by a physiologic sac, the     days under sterile technique in the NICV. The infant is returned
 pediatric surgeon has many options available regarding            to the operating room for removal of the prosthesis and a formal
 omphalocele treatment. Case management depends on the set
 of clinical circumstances and the anatomy that
                                                        PART VI Abdominal Wall, Peritoneum, and Diaphragm                431



closure of the abdominal wall. When the silo is removed, the          manifest gastroesophageal reflux postoperatively as a result of
major portion of the sac is excised except for the segment that       increased abdominal pressure caused by the repair of the smaller
is adherent to the liver. Some surgeons remove the sac at the         than normal abdominal cavity. In a few patients, an antireflux
initial operation to evaluate the intraabdominal viscera for          procedure may be necessary to allow discharge from the
possible bowel atresias, vitelline duct anomalies, or other intra-    hospital. There is also an increased risk of inguinal hernia
abdominal defects.                                                    because of the elevated intra-abdominal pressure.
   On rare occasions, when the defect is large (> 1 0 cm) and            The overall survival for infants with omphalocele depends on
takes up much of the anterior abdominal wall and the infant has       the size of the defect, whether the infant is premature, if the sac
a small abdominal cavity with limited right of domain for the         ruptures, and how many and of what severity associated
herniated viscera, or in cases of suspected chromosomal               anomalies coexist. Mortality is related directly to the severity of
syndromes (trisomies 13 through 15 or trisomies 16 through            coexisting defects and the presence of chromosomal conditions
18), nonoperative management using topical application of an          inconsistent with long-term survival. Infants with chromosomal
escharotic agent is an alternative choice of treatment. Topical       syndromes and infants with Cantrell's pentalogy have a
therapy is also useful as a temporizing measure in infants with       significant mortality (75%). Most infants with Cantrell's
severe unstable cardiac defects (hypoplastic left heart,              pentalogy die as a result of cardiorespiratory failure and sepsis.
hypoplastic aortic arch) and in premature infants with an             Infants with lower midline syndrome rarely have congenital
omphalocele complicated by hyaline membrane disease,                  heart disease, and even if there is a myelomeningocele, they
persistent pulmonary hypertension, or sepsis. As long as the sac      rarely have problems with hydrocephalus. Repair of
remains intact, definitive repair can be delayed until the infant's   infants with lower midline syndrome is often complex, with
cardiac condition is treated or the pulmonary status is               bladder reconstruction commonly performed with intestinal
improved. Escharotic agents include 0.25% merbromin                   augmentation and Mitrofanoff drainage, reconstruction of the
(Mercurochrome) and 0.5% silver nitrate solution. _ce-daily           genitalia, orthopedic repair of the widely separated pubic rami,
applications allow the sac to thicken and epithelialize. The          and cutaneous enterostomy. There is a small group of infants
initial use of merbromin in Europe employed a 2 % solution.           with omphaloceles who have hypoplastic lungs. These infants
This concentration resulted instances of mercury poisoning,           require long-term ventilator support, often have permanently
however, and was abandoned. The current concentration of              limited respiratory reserve, and frequently have a high
0.25% has not been associated with any significant                    postoperative mortality. Overall mortality ranges from 25% to
complications. Silver titrate solution is bacteriostatic and          60% in reports from various institutions and in our own experi-
encourages epithelialization. Because the 0.5% solution is            ence has been 30%.
hypotonic, loss of sodium from the sac into the dressing has
been observed and may cause hyponatremia. Silver nitrate              SUGGESTED READINGS
solution also stains linens, bed sheets, and the infant's and
caretakers' skin gray-black. Large sheets of Op-site as a semi        Allen RG, Wrenn EL Jr: Silon as a sac in the treatment of omphalocele
permeable wound cover over the intact sac has been suggested                   and gastroschisis. J Pediatr Surg 4:3, 1969. This article
by some investigators. Epithelialization can occur beneath the                 describes a simple modification of the Schuster technique
Op-site, and downward pressure over the sac contents aids in                   currently adopted by most pediatric surgeons for cases of
the reduction process. If sac rupture occurs, the remaining sac                gastroschisis that cannot be repaired primarily.
and its contents may be covered temporarily with a biologic
dressing, such as amnion, a homograft of human skin, or               Fonkalsrud EW, Smith MD, Shaw KS, et al: Selective management of
pigskin heterografts. The disadvantages of topical therapy                     gastroschisis according to degree of visceroabdominal
include the potential for subsequent sac rupture, local infection,             disproportion. Ann Surg 218:742,1993.
                                                                               How to determine which patients may have primary repair
prolonged hospitalization, and a huge residual ventral hernia.
                                                                               and which require staged repairs.
The topical therapy should be used for only a few weeks at
most because the abdominal muscles should be stretched as             Grosfeld JL, Weber TR: Congenital abdominal wall defects:
early as possible or the resulting massive skin-covered ventral                 Gasttoschisis and omphalocele. Curr Probl Surg 19:157, 1982.
hernia ill be difficult to repair and be associated with high                   A thorough discussion of all aspects of the major abdominal
mortality. These factors have convinced us to use this                          wall defects.
technique sparingly.
After operative repair, infants with an omphalocele have a            Pokorny W], Harberg FJ, McGill CW: Gastroschisis complicated by
moderate risk of developing complications. Sepsis may occur                   intestinal attesia. J Pediatt Surg 16:261, 1981. This important
and may be related to the presence of a prosthetic silo. The                  early report documents the care of infants with gastroschisis
infant with an omphalocele can be nourished by enteral                        complicated by intestinal atresia.
feedings much more quickly than neonates with gastroschisis.
Because the sac is intact in most patients, the bowel has not         Schuster S: A new method for the staged repair of large omphaloceles.
been exposed to the irritating effects of amniotic fluid and is                 Surg Gynecol Obstet 125:261,1967.
relatively normal in 1pearance and function. Some infants with                  The classic description of staged repair of giant abdominal
omphalocele                                                                     wall defects.

								
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