Emily M. Fontenot
Sean E. Mclean
Presentation
A 34-year-old primagravida female is referred to your office by her obstetrician after an abdominal wall defect with herniation of small bowel and liver was noted on her first-trimester ultrasound. She presents for counseling concerning the child’s delivery and surgical options for repair. A fetal ultrasound is performed that revealed an omphalocele with no other anomalies. Karyotype was performed that revealed a normal male karyotype (46, XY). The mother continues along in her pregnancy with frequent ultrasounds, and the remainder of the pregnancy is unremarkable. She gives birth to a 38-week estimated gestational age male infant via normal spontaneous vaginal delivery with APGARS 8 and 9 at 1 and 5 minutes, respectively. His lower extremities and abdomen are placed into a sterile abdominal bag, and he is transferred to the neonatal intensive care unit.
Differential Diagnosis
Of the types of congenital abdominal wall defects, omphalocele and gastroschisis represent the most common. Omphalocele is a midline anterior abdominal wall fascial defect >4 cm. The rectus muscles are present and normal but insert widely on the costal margins and do not meet in the middle at the xiphoid. The resultant defect allows for herniation of the midgut and other abdominal viscera. The herniated organs are contained within a membranous sac that consists of peritoneum, Wharton’s jelly, and amnion. The umbilical cord inserts on the apex of this membrane. Small omphalocele contains small bowel with or without stomach and has a fascial defect <5 cm. Giant omphalocelecontains bowel, stomach, and liver and has a defect >5 cm. Ruptured omphalocele is the third presentation of omphalocele where the sac has ruptured in utero or during birth.
Gastroschisis is a full-thickness abdominal wall defect that occurs just to the right of a normally inserted umbilical cord. The herniated bowel and abdominal viscera are not covered by a membrane. The viscera are subjected to exposure to amniotic fluid during gestation.
There are other types of abdominal wall defects and syndromes that involve congenital abdominal wall abnormalities. An umbilical hernia is an abdominal wall defect caused by a persistent umbilical ring and is covered by skin. Pentalogy of Cantrell is a rare congenital abnormality characterized by omphalocele, anterior diaphragmatic hernia, malformation or absence of the pericardium, sternal cleft, and cardiac malformations. Ectopia cordis thoracis is due to partial or complete failure of midline fusion of the sternum resulting in the heart protruding from the chest through a split sternum. In contrast to the Pentalogy of Cantrell, the heart is not covered by a membrane in ectopia cordis thoracis. Lastly, prune belly syndrome is a constellation of anomalies including deficient or absent abdominal wall muscles, bilateral cryptorchidism, and a dilated dysmorphic urinary tract.
Workup
On physical examination, the newborn patient has a fascial defect of 6 cm with small bowel and liver herniated through his umbilicus and covered by a translucent sac with the umbilical cord inserted at its apex (Figure 1). Chest x-ray, echocardiogram, renal ultrasound, and skeletal radiography are performed and note no abnormalities. Routine laboratory tests are run and are all within normal limits, including blood glucose of 115 mg/dL.
FIGURE 1 • Giant omphalocele with small bowel and large portion of the liver herniated through the defect.
Discussion
Omphalocele occurs due to a failed midline fusion of the lateral embryonic folds and unsuccessful return of the midgut into the abdominal cavity. The incidence of omphalocele is 1 in 5,000 live births. Omphaloceles are more commonly seen in males, infants born to multiparous women, twin or multiple births, infants born to African American females, families with a history of omphalocele, and with advanced maternal age (>30 years). Omphalocele can present as a part of a syndrome (Beckwith-Wiedemann, OEIS [omphalocele, exstrophy, imperforate anus, and spinal anomalies], Gershoni-Baruch, Donnai-Barrow) or with an associated chromosomal abnormality (trisomy 13,14, 15, 18, or 21). Fifty percent to seventy percent of patients with an omphalocele will have at least one associated anomaly. Cardiac defects represent the most frequent anomaly occurring in 30% to 50% followed by musculoskeletal, gastrointestinal, and genitourinary abnormalities. Chromosomal abnormalities occur in 30%. Most frequently these are trisomies 13, 14, 15, 18, and 21. Omphalocele has also been seen with Turner’s syndrome and triploidy. Beckwith-Wiedemann syndrome is associated with an umbilical defect, which is characterized by macroglossia, hyperinsulinemia, and organomegaly, as well as an increased risk of Wilms’ tumor, hepatoblastoma, and neuroblastoma. The umbilical defect may result in omphalocele or umbilical hernia. Omphalocele is also part of the OEIS complex, which involves omphalocele, bladder exstrophy, imperforate anus, and spinal defects. Lower midline syndrome includes exstrophy of the bladder or cloaca, vesicointestinal fissure, colon atresia, imperforate anus, sacral vertebral defects, and lipomeningocele or meningomyelocele. Whether the size of the defect correlates with association of other anomalies remains to be determined and continues to be the subject of investigation.
Management
Management of omphalocele involves care of the fetus and mother upon discovery of the omphalocele during prenatal ultrasound. Omphalocele can first be detected by ultrasound at 10 to 14 weeks. The sensitivity of detecting an omphalocele on antenatal ultrasound is 75%. After the diagnosis is established, further prenatal testing is performed to assess for the presence of other congenital abnormalities and genetic alterations that may be life threatening or lead to fetal demise. Elevated maternal serum and amniotic fluid alpha fetoprotein can be found with omphalocele and other abdominal wall defects. Fetal karyotype is recommended due to the high incidence of chromosomal abnormalities associated with omphalocele. In a fetus with omphalocele, there is a 50% chance of a congenital heart abnormality; thus, fetal echocardiography is recommended to evaluate for cardiac anomalies. Serial ultrasounds and close prenatal surveillance must be performed because the fetus with omphalocele is at increased risk for fetal growth retardation, polyhydramnios, and intrauterine death.
After the diagnosis of omphalocele is confirmed, prenatal counseling should be provided by a multidisciplinary team that includes a pediatric surgeon to provide the parents with an overview of the postnatal and surgical management of the future newborn patient. Delivery for omphalocele should occur in a tertiary care center with advanced neonatal and pediatric surgical support. Mode and timing of delivery is determined by the obstetrical team. There is no benefit to delivery prior to 37 weeks’ gestation. During delivery there is a risk of dystocia, sac rupture, and injury to abdominal viscera; therefore, special care and preparation must be taken. Cesarean section should be performed for giant omphalocele. Vaginal delivery is appropriate for small omphalocele.
Initial postnatal care and management should focus upon stabilization of the newborn and prevention of injury to the sac and its contents. Rupture of the sac increases the risk of infection, intestinal injury, or hepatic trauma. With compromise of the sac or its contents, the option for delayed closure will be lost. After birth, the infant must immediately be evaluated for pulmonary or cardiac compromise by routine birth assessment. Some infants may require supplemental oxygen, or intubation and ventilator support. Patients with a giant omphalocele may be at risk for pulmonary insufficiency from pulmonary hypoplasia. Such patients may require prolonged ventilation, advanced modes of ventilator support, or extracorporeal life support.
Upon confirmation of cardiovascular and pulmonary stability, intravenous (IV) access is established. Peripheral IV catheters are sufficient for immediate postnatal resuscitation. Many infants with omphalocele will require parenteral nutrition; thus, early central venous access is preferable. Umbilical vessels should not be used for access because the course of the umbilical vessels is abnormal due to the omphalocele. Furthermore, the vessels are ligated at the time of repair.
With established access, patients are immediately placed on D10/0.25 normal saline IV fluid at a rate of 140 to 150 mL/kg/d. With the demonstration of adequate hydration, the fluid rate can be scaled back to a maintenance rate of 80 to 100 mL/kg/d. With an intact sac, fluid loss is not excessive. A ruptured sac can lead to high fluid loss. These patients should be maintained at the higher fluid rate (140 to 150 mL/kg/d); fluid boluses (20 mL/kg of 0.45 normal saline) should be administered when clinically indicated.
After fluid resuscitation has begun, two aspects of management are of particular importance in babies with omphalocele. First, the baby with omphalocele is at significant risk for hypothermia. Temperature must be closely monitored, temperature in the resuscitation room should be elevated, the newborn should be placed in an isolette with a warmer, and the omphalocele should be covered with plastic wrap to maintain body heat. Second, close glucose monitoring is essential. Due to the association between omphalocele and Beckwith-Wiedemann syndrome, tight glucose monitoring must be performed until the syndrome is ruled out.
Further management includes the placement of a replogle and urinary catheter for gastric and bladder decompression. Antibiotics and Vitamin K are administered. The baby is assessed by physical examination and appropriate imaging for other anomalies. After the initial resuscitation, all infants with omphalocele receive an echocardiogram to evaluate for heart abnormalities.
After the child is deemed stable, the membranous sac is evaluated to look for areas of disruption. The size of the fascial defect is also noted at this time. Next the omphalocele should be covered to protect the sac, to prevent insensible evaporative fluid loss, and to minimize heat loss. Wet gauze may accelerate hypothermia; thus, Xeroform or other nonadherent dressing should be placed around the sac. A second layer with dry mildly compressive gauze should be wrapped around the omphalocele. A third layer of plastic wrap may also be applied. If the child will require transfer to a tertiary care center, then the infant’s lower extremities and abdomen should be placed into a sterile bowel bag in preparation for transfer. As long as the membrane is intact, closure is not paramount and should be delayed until the neonate has been stabilized and other anomalies have been ruled out. If the membrane has been violated, the viscera should be placed in a spring-loaded silo. The silo should be placed in the operating room or in a sterile setting at the isolette in the neonatal intensive care unit with the support of an operating room team.
Surgical Approach
Repair of omphalocele should be performed under planned and controlled circumstances. Prior to repair, a stable cardiopulmonary state must be achieved. The patient should be appropriately evaluated for cardiac defects by echocardiogram and other associated anomalies. Patients with Beckwith-Wiedemann syndrome require aggressive management of serum glucose. Children must have a karyotype performed. The presence of trisomy 13 or 18 may change the overall clinical plans for the patient (Table 1).
TABLE 1. Key Technical Steps and Potential Pitfalls in Surgical Management of Omphalocele
The goals of surgery for omphalocele are to reduce the viscera into the abdominal cavity and to close the skin and fascia. Children with omphalocele will have a reduced abdominal domain. Forced placement of the viscera into the abdomen places the patient at risk for an abdominal compartment syndrome. The amount of viscera that requires reduction in relation to the size of the abdomen is a key factor in determining the timing and the type of surgical closure. Other equally important factors are the size of the fascial defect and the overall physiologic state of the patient.
For an omphalocele <5 cm, a primary closure is the best option. Closure involves removal of the sac at the level of the skin. If there is residual sac covering the liver, some sac can be left to avoid injury to the capsule of the liver. The umbilical vessels and urachus are suture ligated. Skin flaps are raised to expose the fascia. Some surgeons will manually stretch the muscles and fascia to increase abdominal domain. As the viscera are reduced, it is important to communicate with the anesthesiologist to avoid the creation of an abdominal compartment syndrome; furthermore, care must be taken with the liver during reduction to avoid torsion of the hepatic veins, disruption of portal vein inflow, or hemorrhage from injury to the liver capsule. With respiratory or hemodynamic compromise, temporizing measures must be taken for closure of the abdomen. The midgut should be reduced first followed by the liver. Once the viscera are reduced with no signs of compartment syndrome, the fascia is closed in the midline. If midline closure is not possible, transverse closure is acceptable. Simple or mattress stitches are placed through the abdominal wall (except skin) with absorbable suture. The skin is closed with a running absorbable suture. An umbilicoplasty is performed if there is sufficient skin.
Primary closure may not be an option due to an increase in abdominal pressure or a wide gap in the fascia. In such cases, there are multiple options for closure. Skin closure is a temporary closure strategy. Fascia is closed as permitted. Skin flaps are created and the edges closed. A small ventral hernia remains that is repaired at a later date. Another temporizing method is to bridge the fascia with nonabsorable (Gortex, Marlex), absorbable (Vicryl, Dexon), or biologic mesh (Alloderm, Surgisis). Skin flaps are mobilized to cover the mesh. Nonabsorbable graft is a temporary option. The mesh is removed and fascia closed after the child has grown. The potential complications with nonabsorbable mesh include infection, seroma, and fistula. Absorbable graft material (Vicryl, Dexon) provides favorable short-term results, but the repair will weaken over time leaving a ventral hernia. Such hernias should be repaired when the child has grown sufficiently to allow for a primary fascial closure. Biologic mesh will incorporate into the fascia and stimulate fibroblast in-growth. There are no large series for biologic mesh that have determined the efficacy and the complication rates.
Staged reduction and closure is employed for a small omphalocele that cannot be closed primarily, a large omphalocele with a high volume of herniated viscera, or a wide fascial defect. The key principle is to provide temporary coverage while the viscera are gradually reduced into the abdomen. Temporary coverage can be achieved with a silastic silo (sewn to the edges of the fascia) or a spring-loaded silo suspended from the isolette. Pressure is applied by placing ties or sutures on the silo to push the viscera into the abdomen. A third technique involves sewing sheets of gortex or silastic to opposite ends (or sides) of the fascia. The closure is gradually tightened by cutting out a portion of each sheet in the center and closing it with a new suture line. This is done every 2 to 3 days until the fascial edges are close enough to perform a primary closure.
For patients with a giant omphalocele or that are too unstable for surgery, the “paint and wait” technique with or without compression is the best option. The hernia sac is coated with an antimicrobial agent that allows the sac to toughen into an eschar. Currently, silver sulfadiazine (Silvadene) is the treatment of choice due to its broad-spectrum antimicrobial activity, little toxicity, and ease of daily application. Mercurochrome, Betadine, and silver nitrite are no longer used because they create metabolic and electrolyte derangements. The hernia sac is coated with an antimicrobial agent that causes the sac to toughen into an eschar. As the sac contracts, the infant continues to grow. A large ventral hernia develops that can later be repaired primarily, with muscle flaps or a biocompatible mesh. Compression can be added by wrapping an elastic bandage around the sac. The bandage should assume the conformation of a cone and is carried around the back of the patient to create compressive forces toward center of the abdominal cavity. The addition of elastic bandage compression may speed the process of reduction of the viscera and increase the likelihood of a delayed primary fascial repair. “Paint and wait” usually takes 6 to 12 months before definitive closure is achieved.
Postoperative Management
Systemic antibiotics should be continued for 5 to 7 days following the procedure or until the prosthesis is removed. IV fluid at an initial rate of 140 mL/kg/h should be started and titrated for a urine output of at least 1 mL/kg/h. Parenteral nutrition by a central venous catheter should continue until bowel function returns. A prolonged ileus, as seen with gastroschisis, is not expected. If bowel function fails to return by 3 weeks, a contrast bowel study should be ordered to rule out other gastrointestinal pathology.
Case Conclusion
In the present patient, primary closure of the defect was not plausible. As our patient had no other pathology, we elected to perform a staged repair. Nonadherent gauze was placed over the Silvadenecoated membrane. An external compression bandage was then wrapped around the externalized viscera and around the infant (Figure 2).
Over the next week, the viscera were slowly reduced. On the tenth day of life, the infant was taken to the operating room where the defect was closed primarily. Parenteral nutrition was continued until bowel function returned. The infant was discharged to home on day of life 21.
FIGURE 2 • Elastic compression bandages are placed around the omphalocele around the infant to gradually reduce the herniated viscera.
Complications
Many of the complications of omphalocele repair can be attributed to the increase in abdominal pressure that results from reduction of the herniated viscera into an abdomen with inadequate domain. Pulmonary compromise and abdominal compartment syndrome can result. It is not infrequent for these infants to develop indirect inguinal hernias following repair due to dilation of the internal ring from increased intra-abdominal pressure. There is no need for immediate repair as this may act as a “pop off” valve releasing excess pressure. Repair is delayed until comorbid conditions resolve. An increased incidence of gastroesophageal reflux may also occur due to the increase in pressure.
As with any abdominal operation, there remains a risk for adhesions to develop. Intra-abdominal wall infections may lead to wound separation, dehiscence, or sepsis. The presence of a prosthesis increases this risk. Complications related to catheter infection and decline in liver function from prolonged parenteral nutrition remain a threat. Due to abnormal fixation and rotation of the intestine, a child with an omphalocele has malrotation; however, corrective repair does not take place at the time of the abdominal wall defect repair. Therefore, complications related to malrotation and midgut volvulus are occasionally observed.
Outcomes
The overall mortality in live birth with omphalocele is 10% to 25%. There is no general consensus on whether there is a relation of the size of the defect to the outcome. However, an increase in the incidence of an unfavorable outcome has been shown with exteriorization of the liver. Outcomes related to omphalocele are dependent upon comorbid conditions. Infants with an isolated omphalocele, regardless of size, have a 75% to 95% survival. In those with a large omphalocele, prognosis and outcome are related to associated pulmonary complications (pulmonary hypoplasia).
TAKE HOME POINTS
· 50% to 70% of infants with omphalocele has an additional congenital anomaly with cardiac defects occurring in 30% to 50% of cases.
· Early strict glucose monitoring is paramount until Beckwith-Wiedemann syndrome can be ruled out.
· When the membrane is not ruptured, repair is delayed until other pathology is ruled out.
· The goal of repair is primary closure with no increase in intra-abdominal pressure.
· In the unstable infant, the “Paint and Wait” technique should be employed.
· Morbidity and mortality are largely due to concurrent anomalies.
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