Defect in the closure of the abdominal wall Omphalocele and gastroschisis |
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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.
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Complications |
The intestines outside the abdominal wall are susceptible to infection, dehydration, trauma,
or impaired blood flow.
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Frequency |
1 in every 4,000 births.
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Associated defects |
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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.
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Hypoglycemia occurring immediately after birth can result in brain damage and mental
retardation, although the hypoglycemia resolves later.
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Inheritance pattern |
Unknown - in a small number of families, autosomal dominant
and X-linked inheritance have been found.
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Penetrance |
Unknown.
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Risk of recurrence |
Not known with certainty.
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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.
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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.
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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.
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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.
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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.
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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.
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Frequency |
1 in 6,000 births.
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Inheritance pattern |
The defect is not considered hereditary.
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Risk of recurrence |
There is no precise information, but it is usually not high.
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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.
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Molecular genetic information |
The gene for the disease
No specific gene for gastroschisis is known
Location
No gene is known.
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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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