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What is an omphalocele?
An omphalocele is a congenital (present at birth) malformation of the abdominal wall in which abdominal contents protrude into a thin-walled sac outside of the abdominal cavity. The protrusion occurs at the base of the umbilical cord.
As the fetus develops between the 6th and 10th weeks of pregnancy, the intestines get longer and extend or push out from the abdomen into the umbilical cord. By the 11th week of development, the intestines normally return to the abdominal cavity. If this fails to happen, an omphalocele occurs.
The omphalocele may be small, with only a portion of the intestine protruding outside the abdominal cavity, or it may be large, with most of the abdominal organs (intestine, liver and spleen) outside the abdominal cavity.
Since some or all of the abdominal organs are outside the body, the abdominal cavity does not grow to its normal size, so it may be too small to hold the abdominal organs. The exposed organs can be more easily injured.
The cause of omphalocele is unknown, but it is not related to anything a mother may have done during pregnancy. More than two-thirds of babies with an omphalocele have abnormalities of other organs or body parts, most commonly the spine, digestive system, heart, urinary system and limbs.Thirty percent have a chromosomal (genetic) abnormality, most commonly Trisomy 13, Trisomy 18, Trisomy 21, Turner syndrome or triploidy.
What does an omphalocele look like?
An omphalocele is covered by a clear sac or membrane that is attached to the umbilical cord. The sac may contain only a small loop of bowel or most of the bowel and other abdominal organs.
If the sac ruptures, the abdominal contents move through the opening in the abdominal wall. In many children, the abdomen is smaller than usual, making placement of the abdominal contents back into the abdomen quite difficult.
Who is at risk for developing an omphalocele?
When no other birth defects are present, the risk for an omphalocele occurring in a future pregnancy is 1%. Some infants with an omphalocele have a syndrome known as Beckwith-Wiedemann syndrome. This syndrome is characterized by heavy birthweight and an enlarged liver, spleen and tongue.
Other characteristics include low blood sugar in the newborn period, malformations around the ear, asymmetric growth of the body, and tumors of the liver and adrenal glands. The syndrome is thought to be caused by an overactive oncogene called IGF2. Oncogenes control cell growth; if mutated, uncontrolled cell growth may result.
How often does an omphalocele occur?
A small omphalocele in which there is protrusion of only a small portion of the intestine occurs in 1 out of every 5,000 live births. A large omphalocele in which there is a protrusion of the intestines, liver and other organs occurs in 1 out of every 10,000 live births.
How is an omphalocele diagnosed?
Omphaloceles are often detected with fetal ultrasonography in the second and third trimesters of pregnancy. A fetal echocardiogram (ultrasound of the heart) may also be done to check for heart abnormalities before the baby is born.
After birth, physical examination reveals an omphalocele. Other diagnostic tests (echocardiogram, chest X-ray and abdominal ultrasound) must then be performed to determine the presence of other abnormalities.
How is an omphalocele treated?
A number of factors play a role in determining the course of treatment. These factors should be discussed and a joint decision by parents and physicians should be made as to the optimal treatment for each individual child. Significant factors include:
- The child’s medical history, prematurity and the presence of other malformations and chromosomal anomalies
- The baby’s tolerance for specific medications, procedures, or therapies
Surgery to Treat Omphaloceles
- If the omphalocele ruptures, urgent surgery is performed.
- For small omphaloceles, surgery is generally performed shortly after birth to return the organs to the abdomen and close the opening in the abdominal wall.
- Larger omphaloceles often require gradual reduction by enlarging the abdominal cavity to accommodate the intestinal contents. The repair is thus done in stages and most often requires the placement of a plastic silo or patch.
A plastic silo is placed over the abdominal organs protecting the bowel and permitting reduction until surgical closure of the abdominal wall can be done.
Because the abdomen is usually small and underdeveloped, it may not be possible to return the organs to the abdominal cavity all at once. Through daily applications of gentle pressure to the silo, organs are gradually moved back into the abdomen over several days or weeks.
If the organs can be returned to the abdominal cavity without compromise of the babies respiration or circulation, the abdominal wall is closed surgically either using the muscles of the abdominal wall or a plastic patch made of gortex.
Since it may not be possible to close the abdominal wall muscle in some cases of extremely large omphaloceles, a large plastic patch of gortex covered by skin is used. Over the next 12 to 36 months, partial removal of the patch and excess skin is performed. Once the abdominal cavity has grown sufficiently to accommodate the abdominal organs the plastic patch is fully removed, the muscles of the abdominal wall closed, and the skin incision repaired. Help from a mechanical ventilator (breathing machine) may thus be temporarily needed while swelling decreases and the size of the abdominal cavity increases.
In unstable infants who cannot tolerate surgery, an antibiotic cream is applied to toughen the sac. Over several months, the child’s skin grows gradually and replaces the omphalocele sac. Surgery is postponed for 6 to 12 months in order to allow the abdominal cavity to enlarge as the baby grows.
What is the long-term outlook for a baby with an omphalocele?
Possible problems are dependent upon the size of the omphalocele and the extent of other abnormalities. When no other complicating anomalies are present, more than 90% of infants survive. When other anomalies are severe, survival is approximately 70%.
Source: Cincinnati Children’s Hospital Medical Center