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Omphalocele

An omphalocele is a covered defect of the umbilicus (belly button) with a “sac” which contains abdominal contents. The skin and the muscle of the abdomen are missing. This problem is thought to start in the third week of development when the intestines elongate and normally reside in the yolk sac outside of the abdomen. Omphaloceles are covered by a sac composed of an outer layer and an inner layer. The umbilical cord inserts right into the sac. A separate compartment containing a jelly-like material also may be observed. If the omphalocele is above the umbilicus there may be other defects involving the diaphragm, sternum, and heart. If the omphalocele is below the umbilicus there may be other defects affecting the bladder, rectum, and lower spinal cord.

The occurence of omphalocele is approximately 1 in 5000 live births. Boys are affected more often than girls. Infants with an omphalocele have a number of other abnormalities or anomalies. More than 50% of cases have other serious problems involving the gastrointestinal tract (stomach and intestines) and the cardiovascular (heart), genitourinary (kidneys and bladder), musculoskeletal, and central nervous systems (brain and spinal cord). Many infants born with an omphalocele are premature. Others may be affected by abnormal chromosomes, including Beckwith-Wiedemann syndrome characterized by gigantism, large tongue, and an umbilical defect in the form of either a hernia or an omphalocele. Infants with Beckwith-Wiedemann syndrome have abdominal organs that are large and a problem with the pancreas that may result in low blood sugar that can lead to seizures in the newborn period. These infants also have an increased incidence of cancer of the kidneys, liver, and adrenal glands. Omphalocele may occur in infants with other serious genetic problems such as extra chromosomes.

When the omphalocele is located below the umbilicus, it often is associated with a lower midline syndrome, which includes opening of the pelvic organs (bladder, rectum, uterus) outside of the abdomen and lack of development of the colon, vagina, and anus. (Fig. 1). Repair of infants with lower midline syndrome is often complex requiring bladder reconstruction, reconstruction of the genitalia, repair of the pelvic bones, and creation of an opening of the intestines onto the abdominal wall.

Problems with the spinal cord and abnormal development of the lower backbone are also observed in many cases. It is often difficult to distinguish boys from girls from the genitalia, with a very short penis in boys, and sex assignment must be considered carefully at an early stage. An omphalocele located above the umbilicus may be part of Cantrell’s pentalogy, which includes omphalocele, a hole in the diaphragm, an opening in the sternum (breast bone), heart defects (most commonly a hole inside the heart connecting 2 of its chambers), and occasionally the heart located outside of the chest (Figure 2).

An omphalocele defect may vary from 1 inch to greater than 4 inches in diameter; the smaller the defect, the better the prognosis. Many smaller defects (<4 cm) represent “herniation of the umbilical cord”—a minor form of omphalocele which is fairly easy to close (Figures 3 and 4). These smaller omphaloceles probably occur in the 8th to 10th week of pregnancy. An umbilical cord hernia usually contains only small intestine. In contrast, although the large omphalocele contains small intestine, the liver (35% of patients), large intestine, and stomach are often present within the sac.

Figure 3: 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 4: A) A giant omphalocele. Note the covering or “sac” over the intestines. The white arrow points to the liver which is in the omphalocele. B) A small omphalocele, often called a “hernia of the umbilical cord”.

The location of the abdominal organs outside of the abdomen during pregnancy results in a small abdominal cavity that may make attempts at reducing the sac contents extremely difficult. The intestines are not usually in the normal position nor are they fixed to the back of the abdomen. The diagnosis of omphalocele can be made by prenatal ultrasound examination (Figure 14).

Figure 5: A) and B) Prenatal diagnosis of omphalocele and ectopia cordis (heart outside of the chest) by ultrasound. The drawings on the left illustrate what is seen in the ultrasounds. A scan in the plane illustrated in drawing A shows a large mass that extends outside of the chest (See ultrasound A). The umbilical vein/ductus venosus (UV/DV) joins the left portal vein (LPV) which is in the liver. 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. JAMA 246:774, 1981, and Nakayama DK, Harrison MR, Gross BH, et al: Management of the fetus with an abdominal wall defect. J Pediatr Surg 19:408, 1984.)

 

The early detection of omphalocele allows for maternal counseling, optimal delivery planning, and referral of the affected mother to a high-risk delivery center supported by a contemporary NICU and pediatric surgical expertise. Prenatal ultrasound studies can help distinguish between omphaloceles with a probable good outcome, such as a small omphalocele or hernia of the umbilical cord, and those with a more guarded outcome, including a large omphalocele in fetuses with multiple abnormalities and syndromes that have high perinatal death and complication rates. If the liver is recognized outside the abdomen within the sac, the defect is usually large; however, the infant’s prognosis also depends on the presence or absence of other serious abnormalities. If the defect is large, the mother commonly requires a Cesarean section. With the exception of a large omphalocele, Cesarean delivery has little advantage over a vaginal delivery in the management of most abdominal wall defects. Amniocentesis, or sampling of the fluid around the fetus, as well as direct fetal blood sampling may assist in making the diagnosis of omphalocele and abnormalities in the chromosomes. This is particularly useful in women with advanced age (35 to 45 years) in whom the risk of the fetus having an extra chromosome is two to three times greater than in younger women.

At birth, the emergency care of newborns with omphalocele includes the insertion of a tube through the mouth and into the stomach to remove any swallowed air and to prevent distention of the intestines, which may interfere with attempts to reduce the intestines back into the abdomen. The intact omphalocele sac should be kept covered, protected from injury, and the infant kept in a heated environment. If the sac is large and collapsing to one side or the other, the sac should be supported by a sterile gauze dressing that wraps around the infant’s back. Intravenous fluids are administered. The fluid losses are usually not excessive because the intestines and other organs are covered by an intact sac.

Approximately 10% of patients have a rupture of the omphalocele sac (Figure 11). In these instances, loss of fluid is much greater and similar to the fluid losses of infants with gastroschisis. These patients require more fluids. Antibiotics are given. The infant’s general condition should be assessed carefully in regard to the heart and the lungs and the possible occurrence of additional congenital anomalies or abnormalities.

Figure 6: Omphalocele at birth (right) and after 3 months of gauze wrapping and skin growth over the omphalocele (left)

Because the abdominal organs are covered by a sac, the pediatric surgeon has many options available regarding omphalocele treatment. The best treatment depends on the clinical circumstances for each patient. Small defects can be managed by closure of the muscle and skin of the abdominal wall. Medium-sized defects are managed by careful removal of the sac with closure of the artery and vein and top of the bladder (urachus) going to the umbilical cord. The abdominal wall is stretched manually on both sides to enlarge the size of the relatively small abdominal cavity. The liver and then the bowel are reduced (placed) into the abdomen. The liver must be placed back into the abdomen carefully to avoid kinking of the blood supply to and from the liver and injury to the liver itself. The abdominal wall cannot be closed right away in patients with large omphaloceles and small abdomens. If the abdominal wall muscle cannot be brought together, closure of the skin alone while leaving a hole in the muscular layer of the abdominal wall may be used in some patients. The resulting hernia can be repaired at a later date. Some surgeons prefer to close the hole in the muscle by insertion of a synthetic material, such as Gore-Tex, Marlex, or an absorbable material.

Initial closure of the omphalocele is usually not possible for infants with large omphalocele defects. These infants often require a “staged” abdominal wall closure using an initial Dacron-reinforced Silastic silo (described earlier under gastroschisis) to temporarily hold the abdominal organs. In placing the silo, the covering sac of the omphalocele does not necessarily need to be removed. The silo may be either be preformed or constructed in the operating room. Antibiotic ointment is placed around the base of the sac where it joins the skin. The contents of the sac are supported by a string suspended overhead. The sac contents can be reduced gradually over 3 to 10 days under sterile technique in the NICU. The infant is returned to the operating room for removal of the silo and closure of the muscle and skin of the abdominal wall. When the silo is removed, the major portion of the sac can be excised except for the segment that is attached to the liver.

In cases of chromosomal problems, nonoperative treatment by applying an inflammatory agent to the surface of the omphalocele is an alternative choice of treatment. This approach is also useful in infants with unstable heart problems and in premature infants with an omphalocele who have lung disease or infection. As long as the sac remains intact, closure of the omphalocele can be delayed until the infant’s heart condition is treated or the lung status is improved. Mercurochrome, Silvadene, or silver nitrate solution can be placed on the surface of the omphalocele. Silvadene and silver nitrate kill germs and encourage the formation of a “skin” over the sac. Most recently, some patients with large omphaloceles have been treated in a similar fashion, instead of with immediate closure of the omphalocele, allowing skin to grow over the omphalocele (Figure 15). This technique is accompanied by wrapping of the omphalocele so as to apply downward pressure over the sac contents to aid in the reduction process. The disadvantage of this approach includes the potential for subsequent sac rupture, prolonged hospitalization, and a huge resulting ventral hernia which may be difficult and even dangerous to repair in the future.

If sac rupture occurs, the remaining sac and its contents may be covered temporarily with a variety of “biologic dressings”, such as amnion, human skin, or pigskin.

After closure of the omphalocele by an operation, infants with an omphalocele have a moderate risk of developing complications. Infection may occur and may be related to the presence of synthetic material. The infant with an omphalocele can be nourished by oral feedings much more quickly than newborns with gastroschisis. Because the sac is intact in most patients, the bowel has not been exposed to the irritating effects of amniotic fluid and is relatively normal in appearance and usually works well. Some infants with omphalocele have gastroesophageal reflux as a result of the increase in the abdominal pressure caused by the closure of the smaller than normal abdominal cavity. In a few patients, an antireflux operation may be necessary. There is also an increased risk of inguinal hernia because of the high abdominal pressure.

The overall survival for infants with omphalocele depends on the size of the defect, whether the infant is premature, if the sac ruptures, and other abnormalities which are present. Death is related directly to the existence of other abnormalities and the presence of chromosomal problems. Infants with chromosomal syndromes and infants with Cantrell’s pentalogy have a significant death rate (75%). Most infants with Cantrell’s pentalogy die as a result of heart and lung failure and infection. There is a small group of infants with omphaloceles who have failure of lung development. These infants require long-term ventilator (breathing machine) support, often have decreased lung function, and a high postoperative death rate. Overall death rates range from 25% to 60% in reports from various institutions.

Article and graphics adapted from O'Neill: Principles of Pediatric Surgery. © 2003, Elsevier.