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Abdominal Wall Defects abdominal cavity
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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