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Skip Navigation LinksHome Page    >    Tests during the pregnancy    >    Defect in the closure of the abdominal wall Omphalocele and gastroschisis
 
 
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Defect in the closure of the abdominal wall Omphalocele and gastroschisis

Omphalocele
(Intestines herniating through the umbilical orifice).

Clinical signs

This is a defect in the abdominal wall manifesting in the herniation of some of the intestines and possibly other organs too outside the abdominal wall. They protrude through the umbilicus (navel), through a ring that surrounds the umbilical cord. The intestines and organs inside the herniated sac in the umbilicus are not covered by skin, only by a transparent membrane. The size of the sac depends on the how extensive the herniation is. Surgical intervention is undertaken immediately after birth and usually has a 50% - 60% success rate. The unsuccessful cases are usually those that are very extensive or accompanied by other defects.

Complications

The intestines outside the abdominal wall are susceptible to infection, dehydration, trauma, or impaired blood flow.

Frequency

1 in every 4,000 births.

Associated defects

These occur in 66% of cases of omphalocele.

The typical defects are heart defects, and defects of the urogenital system and nervous system.

There are also specific syndromes associated with omphalocele, including Beckwith Weidemann syndrome, where the patients have a large tongue and a relatively large body in addition to omphalocele, and Down syndrome.

It is important to test for Beckwith Weidemann syndrome, because early diagnosis soon after birth and appropriate intervention can prevent hypoglycemia (low blood sugar level), which is common in these patients after birth.
Hypoglycemia occurring immediately after birth can result in brain damage and mental retardation, although the hypoglycemia resolves later.

Inheritance pattern

Unknown - in a small number of families, autosomal dominant and X-linked inheritance have been found.

Penetrance

Unknown.

Risk of recurrence

Not known with certainty.

Associated features that can be demonstrated in tests performed during pregnancy

On ultrasound examination, signs of intestinal blockage must be looked for and the size of the defect assessed. Associated defects must be looked for (see above).

Amniocentesis should be considered because of the relatively high risk of chromosome disorders that are associated with this defect. In all these cases it is important to refer the couple for genetic counseling, to which they should bring all available data, including the results of other tests performed during the pregnancy such as alpha-fetoprotein, nuchal translucency, etc.

It is advisable to refer the parents to a multidisciplinary clinic in a hospital for professional counseling by a geneticist, an expert in ultrasound examinations, a pediatric surgeon, and a neonatologist, in order to collate all the data and discuss the various risks in each specific case, the method of monitoring the fetus, possible intervention if indicated, etc. The decisions taken will depend on the severity of the problem, the presence of additional findings, etc.

Molecular genetic information

The gene for the disease

No specific gene for omphalocele is known. In Beckwith Weidemann syndrome a number of genes responsible for the syndrome have been identified.

Location

In Beckwith Weidemann syndrome, the genes responsible are situated on chromosome 11.

Genetic testing

Diagnostic testing

There is no genetic test for diagnosing omphalocele. A number of genes associated with Beckwith Weidemann syndrome have been identified. Only in a very small number of cases of this condition is it possible to identify the genetic mutation. In a small percentage of cases, it is possible to demonstrate in chromosome testing on blood or amniotic fluid an insertion (duplication) of a small segment in chromosome 11. In another small percentage of cases of Beckwith Weidemann syndrome, the mutation has been identified as an asymmetric transfer of genetic information in chromosome 11. In these cases both chromosomes 11 originate from the father rather than one originating from each parent - a condition called uniparental disomy. In the great majority of cases, however, it is difficult to identify the precise mutation, even though the gene in question is known to be situated on chromosome 11. This is a test performed in research laboratories, and it is carried out on an individual basis. The test takes such a long time that it cannot be completed during the course of a pregnancy, and it is not routinely performed apart from in special cases via genetic institutes.

Carrier testing

There are no tests for carrier status of omphalocele.

Fetal testing

There are no genetic tests for diagnosing omphalocele in the fetus.

Gastroschisis
(intestines protruding through the abdominal wall)

Clinical signs

This is a defect in the abdominal wall through which the intestinal loops protrude. The loops are free, appear thickened (edematous) and are not covered with a membrane. The umbilical cord is not involved and enters the abdominal wall, usually on the left of the defect. Infants with this defect usually have a low birth weight.

Complications

The organs (usually intestines) that are outside the abdomen are susceptible to infection, dehydration, trauma or impaired blood flow. In addition, the intestines may twist around their axis, a condition called volvulus. This may lead to necrosis (death) of the intestine or obstruction of the flow of food.

Associated defects

There are usually no associated defects, and the problem is to repair the existing one. If the defect is large, the repair is often difficult and is carried out in stages. The causes of gastroschisis are probably not genetic. The defect in the abdominal wall characteristic of gastroschisis may be caused by impaired blood flow to this region of the abdominal wall during intrauterine life.

Frequency

1 in 6,000 births.

Inheritance pattern

The defect is not considered hereditary.

Risk of recurrence

There is no precise information, but it is usually not high.

Associated features that can be demonstrated in tests performed during pregnancy

On ultrasound examination, signs of intestinal blockage must be looked for and the size of the defect that has to be repaired must be assessed. It is important to ascertain that there is no omphalocele. In all cases, it is important to refer the couple for genetic counseling, to which they should bring all available data, including the results of other tests performed during the pregnancy such as alpha-fetoprotein, nuchal translucency, etc.

It is advisable to refer the parents to a multidisciplinary clinic in a hospital for professional counseling by a geneticist, an expert in ultrasound examinations, a pediatric surgeon, a plastic surgeon, and a neonatologist, in order to collate all the data and discuss the various risks in each specific case, the method of monitoring the fetus, possible intervention if indicated, etc. The decisions taken will depend on the severity of the problem, the presence of additional findings, etc.

Molecular genetic information

The gene for the disease

No specific gene for gastroschisis is known

Location

No gene is known.

Genetic testing

Diagnostic testing

There is no such test for gastroschisis

Carrier testing

There is no such test for gastroschisis

Fetal testing

There is no genetic test for gastroschisis
 
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