INTRODUCTION
The diaphragm is the muscular membrane that separates
the chest cavity, from the abdominal cavity and the oesophagus
and the major blood vessels pass through the diaphragm.
The diaphragm develops in early fetal life, and is usually
fully formed by 9 weeks gestation. In cases of diaphragmatic
hernia, a hole allows structures that are usually within
the abdomen to protrude into the thorax.
The most common site for diaphragmatic hernia is the
left side, through which the stomach, bowel and liver
can pass. The cause of congenital diaphragmatic hernia
is essential unknown, but it often occurs in combination
with other structural malformations, particularly heart
defects. This abnormality is often caused by an underlying
abnormality of the fetal chromosomes, particularly trisomies
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ANTENATAL
The use of ultrasound scanning has lead to some cases
being diagnosed during pregnancy. The diagnosis rests
upon obtaining clear images of the upper abdomen and
chest. The most common finding is displacement of the
fetal stomach, which can usually be clearly seen below
the fetal heart, into the stomach. This sequence leads
to displacement of the fetal heart to the right side
of the chest, and can be distinguished from dextrocardia
by examination of the orientation of the apex of the
fetal heart. Large defects, with significant displacement
of the fetal heart are most easily recognised, and therefore
prenatal diagnosis will select a group with a relatively
poor prognosis. The diagnosis of CDH is most commonly
made at around 20 weeks, as it requires the fetal stomach
to be seen, which is only usually apparent at approximately
18 weeks. Following a diagnosis, the fetus should be
examined for other defects, particularly cardiac defects,
which are present in up to 30% of cases. Even when the
anomaly is apparently, isolated, fetal karyotyping is
strongly recommended, as trisomy 21 and 18 are often
associated with this defect.
The prognosis for CDH diagnosed at this stage of pregnancy
is generally poor, with less than 40% of cases surviving
the first few hours of life. The main cause of death
is pulmonary hypoplasia, caused by compression of the
fetal lungs in utero. This is difficult to predict with
any degree of certainty. Fetal surgery has been attempted
for this condition in the USA, with mixed results. The
operation caries significant risk to both the fetus and
mother and at this time there is no clear evidence that
this intervention carries significant benefits. The procedure
involves opening the uterus, opening the fetal chest
and abdomen to allow a surgical repair to take place.
Theoretically, this could allow development of the fetal
lungs, but the practicalities of when and how to perform
this type of major intervention remain to be clarified.
No centres in the UK are currently offering this type
of surgery.
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POSTNATAL
At birth, there is a transition from oxygenation by
the placenta, to breathing using the lungs. If the lungs
have been compressed by a diaphragmatic hernia then it
will often prove impossible to adequately ventilate the
baby, leading to death by multiple organ failure within
the first few hours of life. The diagnosis of CDH is
suspected in babies who seem well at birth but rapidly
deteriorate and fail to respond to resuscitation. A chest
x-ray will often show the displacement of the stomach
giving the diagnosis in cases that have not been identified
prenatally.
If the baby is able to survive the initial resuscitation
but remains too unwell to undergo immediate surgery there
may be a role for extra corporeal membrane oxygenation
(ECMO), which is practice is a limited number of centres
in the UK. ECMO allows additional oxygen into the circulation
to stabilise the baby before surgery.
The long-term treatment for this malformation is surgical
repair, which not technically complex, but is made hazardous
by the condition of the neonate at the outset of surgery.
If a child is considered well enough for surgery, the
results are usually good. At least 80% will survive surgery
and the majority of these will have completely normal
outcomes, severe hypoxia always caries a risk of cerebral
damage, which may in some cases lead to cerebral palsy
and mental handicap.
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WEST MIDLANDS
DATA
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