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Abdominal Wall Defects

Abdominal Wall Defects


Omphalocele and gastroschisis are congenital defects of an infant's abdominal wall. In each, the anterior abdomen does not close properly, resulting in organs that are normally located within the abdominal cavity remaining outside.

While a baby is going through early stages of development, the intestines grow faster than the abdominal cavity; they elongate in the umbilical sac, which remains open through the first three months of gestation. Toward the end of the first trimester, the intestines normally return into the abdominal cavity and the sac closes, becoming the umbilical cord. In omphalocele, the sac does not close completely, resulting in protrusion of part of the liver or intestines into the open sac. In gastroschisis, the sac closes, but an opening develops next to the umbilical cord (usually on the right) and the intestine remains partially outside the abdomen. The abdominal cavity remains small and underdeveloped.

Omphalocele and gastroschisis can often be detected with prenatal ultrasound. The ultrasonographer usually can identify the omphalocele sac covering the intestines. Omphalocele is frequently associated with other congenital anomalies and additional information about the heart, kidneys, lungs, and intestines can often be obtained during the ultrasound examination. In gastroschisis no sac is present, and intestine can be seen floating in the amniotic fluid.

In both conditions treatment is by surgery soon after birth. Gastroschisis requires urgent surgery since the intestines are outside the abdomen and predisposed to injury and infection. Babies with an omphalocele may be managed semi-urgently, taking time to evaluate the infant for other possible abnormalities. In each condition the initial goal of surgery is to close the abdomen; however, forcing the intestines and other organs back into a small abdomen may result in serious heart and lung problems. Many babies may require application of an external covering, often referred to as a "silo" because of its shape. Over a period of days the intestines can be gently maneuvered back into the gradually expanding abdomen. In 5-10 days the baby returns to the operating room where the silo is removed and the abdomen is closed.

What is an omphalocele?

An omphalocele is a birth defect, which is an abnormality that occurs before birth as a fetus is forming in its mother's uterus. Some of the abdominal organs protrude through an opening in the abdominal muscles in the area of the umbilical cord. A translucent membrane covers the protruding organs.

The omphalocele may be small, with only a portion of the intestine protruding outside the abdominal cavity, or large, with most of the abdominal organs (including intestine, liver, and spleen) present outside the abdominal cavity. Further, the abdominal cavity itself may be small due to underdevelopment during pregnancy.

What causes an omphalocele?

As a fetus is growing in the mother's uterus before birth, different organ systems are developing and maturing. Between the 6th and the 10th weeks of pregnancy, the intestines actually project into the umbilical cord as they are growing. By the 11th week of development, the intestines should return to the abdomen. When the fetus is growing and developing during pregnancy, there is a small opening in the abdominal muscles that the umbilical cord can pass through, connecting the mother to the fetus. As the fetus matures, the abdominal muscles should meet in the middle and grow together, closing off this opening. An omphalocele occurs when the abdominal organs do not return to the abdominal cavity as they should.

It is not known what causes omphalocele. Steps that normally happen in the development of the abdominal organs and muscles simply did not happen properly. It is not known to be caused by anything the mother did during pregnancy.

Who is at risk for developing an omphalocele?

When an omphalocele is isolated (no other birth defects are present), the risk for it to happen in a future pregnancy is one percent or one in 100. There are some families that have been reported to have an omphalocele inherited as an autosomal dominant or X-linked recessive trait. In these cases, the chance for reoccurrence would be higher.

Many babies born with an omphalocele also have other abnormalities. The chance for reoccurrence depends upon the underlying disorder:

  • Thirty percent have a chromosomal (genetic) abnormality, most commonly Trisomy 13, Trisomy 18, Trisomy 21, Turner syndrome, or triploidy.
  • Some infants with omphalocele have a syndrome known as Beckwith-Wiedemann syndrome (an overgrowth malformation syndrome).
  • More than half of babies with omphalocele have abnormalities of other organs or body parts, most commonly the spine, digestive system, heart, urinary system, and limbs.

How often does an omphalocele occur?

A "small" type omphalocele (involving protrusion of a small portion of the intestine only) occurs in one out of every 5,000 live births.

A "large" type omphalocele (involving protrusion of the intestines, liver, and other organs) occurs in one out of every 10,000 live births.

More boys than girls are affected with omphalocele.

Why is an omphalocele a concern?

Since some or all of the abdominal organs are outside the body, infection is a concern, especially if the protective membrane around the organs breaks. Also, an organ may lose its blood supply if it becomes pinched or twisted. A loss of blood flow can damage the affected organ.

How is an omphalocele diagnosed?

Omphalocele can often be detected on fetal ultrasound 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, the omphalocele can be noted by the physician during the physical examination. X-rays (diagnostic tests which use invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs onto film) may also be done after birth to evaluate abnormalities of other organs or body parts.

Treatment for an omphalocele:

Specific treatment for an omphalocele will be determined by your baby's physician based on the following:

  • your baby's gestational age, overall health, and medical history
  • the extent of the condition
  • your baby's tolerance for specific medications, procedures, or therapies
  • expectations for the course of the condition
  • your opinion and preference

For a "small" omphalocele (only a portion of the intestine protruding outside the abdominal cavity), shortly after birth, an operation is done to return the organs to the abdomen and close the opening in the abdominal wall.

For a "large" omphalocele (most of the abdominal organs, including intestine, liver, and spleen are present outside the abdominal cavity), the repair is done in "stages" and may include the following:

  • Initially, sterile, protective sheeting is placed over the abdominal organs.
  • Because the abdomen may be small and underdeveloped, it may not be able to hold all of the organs at once. Therefore, the exposed organs are gradually moved back into the abdomen over several days or weeks.
  • The abdominal wall is closed surgically once the organs have been returned to the abdominal cavity.

Because the abdominal cavity may be small and underdeveloped, and the organs may be swollen, a baby with an omphalocele may have breathing difficulties as the organs are returned to the abdomen. Your baby may need help from a breathing machine called a mechanical ventilator while the swelling is decreasing and the size of the abdominal cavity is increasing.

What is the long-term outlook for a baby born with an omphalocele?

Problems in the future often depend on:

  • the size of the omphalocele.
  • if there was a loss of blood flow to part of the intestine or other organs.
  • the extent of other abnormalities.

Babies who have damage to the intestines or other abdominal organs may have long-term problems with digestion, elimination, and infection.

Consult your baby's physician regarding the prognosis for your baby.

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