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CHAPTER 45

Congenital Diaphragmatic Hernia

and Diaphragmatic Eventration

Merrill McHoney
Kokila Lakhoo

Introduction and formanen ovale, which further worsens the hypercapnia and
Congenital diaphragmatic hernia (CDH) is a group of conditions hypoxia. This vicious positive cycle can lead to severe physiological
characterised by developmental defects in the diaphragm. The cause consequences in those most affected, and lung hypoplasia/pulmonary
is disordered embryogenesis, resulting in incomplete fusion of ele- hypertension is the most detrimental pathophysiological process that
ments giving rise to the diaphragm. CDH occurs at distinctive sites. affects outcome.
The diagnosis can be made in the antenatal period, and can present in Clinical Presentation
the early postnatal period with respiratory distress. Associated lung, History
vascular, and cardiac abnormalities lead to a high mortality (almost
50% overall), and prompt neonatal management is the most important Antenatal
influence on outcome. In this regard, surgical correction has become In countries where routine antenatal ultrasound scanning is performed,
a nonurgent secondary intervention. Chromosomal abnormalities are approximately 50–85% of CDH are diagnosed on antenatal ultrasound
found in 5–30% of cases (trisomy 18 and 13 are the most common). scan. The features present antenatally are:
CDH can present outside the neonatal period in patients with minimal • polyhydramnios;
physiological compromise. The mortality is negligible in this naturally • absent stomach bubble or stomach bubble in chest;
selected group.
• bowel loops in chest;
Demographics
The incidence of CDH is 1 in 2,500 to 1 in 3,500 live births. Left-sided • mediastinal shift; and
CDH is more common than right-sided, with a ratio of 6:1. Bilateral • hydrops.
lesions are reported, but they are invariably fatal. Ninety percent of Foetal magnetic resonance imaging (MRI; see Figure 45.1) is also used
CDH cases are found in a postero-lateral defect (Bochdaleck hernia), in some centres for clarification of the diagnosis, to rule out associated
and 9% are found in an anterio-medial defect (Morgagni hernia). The anomalies, for planning, and for prognostic features. This is not widely
remainder of cases comprise the relatively rarer forms of total absence practiced nor available.
of the diaphragm, absence of the central portion of the diaphragm, and Some features in the antenatal scan are associated with a poorer
oesophageal hiatal hernia. There is no gender or race predisposition.
outcome. These are (1) hydrops, (2) contralateral lung-to-head
Aetiology/Pathophysiology circumference ratio <1.0, (3) diagnosis before 25 weeks gestation, and
The diaphragm arises from four mesodermal elements in the embryo: (4) associated cardiac abnormality. The role of antenatal contralateral
1. the pleuro-peritoneal membrane (fold); lung-to-head circumference ratio in predicting outcome and indication
2. the septum transversum (developing central tendon);
3. the dorsal mesentery of the oesophagus (crural precursor); and
4. somites of the body wall.
Fusion of these elements between the 5th to 8th week of intrauterine
life separates the abdominal cavity from the thoracic cavity. The last
element to close is the pleuroperitoneal membrane, the site of the
Bochdaleck hernia, the commonest form of CDH. Return of the intestinal
organs from the umbilicus around the 10th week of gestation can herniate
into the chest if there is defective diaphragmatic development. Bowel
loops within the chest compress the developing lung and cause lung
hypoplasia (in both lungs, but in particular in the lung on the affected
side). Development of type II alveolar cells that produce surfactant is also
inhibited, resulting in relative surfactant deficiency.
Abnormal development of the pulmonary vasculature leads
to pulmonary hypertension and increased pulmonary vasculature
reactivity. Thus, the affected neonate is prone to episodes of hypoxia and
hypercapnia, which in turn further increase the pulmonary hypertension
and cause persistent foetal circulation. Persistent foetal circulation is a
state of reduced pulmonary blood flow and pulmonary hypertension Figure 45.1: Antenatal MRI scan showing a left CDH at a 32-week scan. Bowel
with severe right-to-left shunting through the patent ductus atreiosus loops are seen in the chest, and there is mediastinal shift.