**2.4. Classification**

There are six types of CHD (**Figure 1**):



**Table 1.** Common chromosome anomalies associated with CDH.

**2. Spectrum of disease**

188 Congenital Anomalies - From the Embryo to the Neonate

Congenital diaphragmatic hernia (CDH) is defined by the presence of an orifice in the dia-

CDH is a rare condition that occurs in <1–5:10,000 births [1]. The most common anatomic type encountered is the left-sided posterolateral hernia (Bochdalek hernia), including the vast majority of cases 85–90%, while the anterior hernia of Morgagni is rare. A bilateral defect accounts for 15–20% of cases; tissue defect involving most of the hemidiaphragm is called agenesis [2].

No cases of CDH in humans have been unequivocally attributed to teratogenic or environmental exposures. Recently, a potential association with the immunosuppressive drug mycophenylate mofetil has been made, but the mechanism by which this drug could cause diaphragmatic

About 10% of all individuals with CDH have a chromosome abnormality. The most common abnormalities are trisomy 18 and isochromosome 12p (Pallister-Killian syndrome or PKS), although many additional abnormalities have been reported (**Table 1**). Some of the more com-

**1.** Posterolateral defect (Bochdalek hernia) occurs most often on the left side and contains

**2.** Parasternal defect (Morgagni hernia), located on anterior retrosternal or parasternal portion of the diaphragm, is rare and more often right-sided or bilateral and usually contains

**3.** Other anterior hernias associated with Pentalogy of Cantrell are rare findings but are usually severe, probably derived from septum transversum. These cases are usually associated with Pentalogy of Cantrell (including defects in the midline abdominal wall

supraumbilical, lower sternum, diaphragmatic pericardium, and heart).

mon monogenic syndromes in which CDH occurs are listed in (**Tables 2** and **3**) [4].

stomach, bowel, and spleen, and if right-sided, contains liver.

phragm that permits the herniation of abdominal contents into the thorax.

**2.1. Definition**

**2.2. Epidemiology**

**2.3. Causes**

*2.3.1. Environmental causes*

defect is unknown [3].

*2.3.2. Heritable causes*

**2.4. Classification**

liver or bowel.

There are six types of CHD (**Figure 1**):


For practical reasons regarding the imaging approach and counseling, it was proposed to classify CDH as intrapleural and mediastinal.

Intrapleural hernias occur through defects in the muscular diaphragm, which may result from deficient fusion of the pleuroperitoneal membranes and abdominal wall musculature or absence of the pleuroperitoneal membranes. Intrapleural hernia contents cause compressions on intrathoracic visceras, causing pulmonary hypoplasia and contralateral mediastinal shift. This category includes the traditionally classified Bochdalek hernias.

Mediastinal hernias can be classified into two types: retrosternal and central. Retrosternal hernias are categorized as Morgagni hernias, although a true Morgagni hernia is only a small anatomic located in the space between the sternal and costal heads of the diaphragm. True Morgagni hernia is considered to be a subtype of retrosternal mediastinal hernias, with larger


**Table 2.** Selected syndromes in which CDH is a feature.

ventral hernias which are defects in the central tendon stemming from septum transversum impaired development. Hiatal hernias, as their name shows, develop more through the esophageal hiatus and do not involve the central tendon. Differentiating ventral mediastinal hernias from intrapleural hernias is important because the intrapleural hernias, usually, do not lead to pulmonary hypoplasia, which is the major complication of CHD [5] (**Table 4**).

the thorax in the early development of the diaphragm. These PPFs are part of the diaphragmatic connective tissue. The membranous diaphragm is later muscularized by migrating muscle precursor cells to the PPF from the cervical somites. This phenomenon happens before these cells proliferate, differentiate, and migrate onto the membranous diaphragm [8, 9]. The hypothesis is that a Bochdalek hernia occurs if the PPFs do not fuse with the septum transversum and the dorsal mesentery of the esophagus by the 10th week of gestation [4].

**Syndrome Gene (locus)** Apert syndrome *FGFR2*

CHARGE syndrome *CHD7* C (trigonocephaly) syndrome *CD96* Coffin-Siris syndrome Unknown Czeizel-Losonci syndrome Unknown Gershoni-Baruch syndrome Unknown Goltz syndrome (focal dermal hypoplasia) *PORCN* Kabuki syndrome Unknown Marfan syndrome *FBN1* Mathieu syndrome Unknown Meacham syndrome *WT1* Microphthalmia with linear skin lesions syndrome *HCCS* PAGOD syndrome Unknown Pentalogy of Cantrell Unknown Poland anomaly Unknown Swyer syndrome Unknown Thoraco-abdominal schisis Unknown

**Table 3.** Syndromes in which CDH is less frequently a feature.

Beckwith-Wiedemann syndrome Dysregulation of imprinted genes on 11p15.5

Congenital Diaphragmatic Hernia

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http://dx.doi.org/10.5772/intechopen.74500

*The lung* originates as an outpouch of the ventral wall of the posterior end of the laryngotracheal tube and divides into two bronchial buds at 3–4 weeks of gestation [10]. As the two buds elongate, the primitive tubular foregut tube begins to pinch into two tubes, namely, the dorsal esophagus and the ventral trachea [11]. Further outgrowth of the lung-buds produces the secondary bronchi. In humans, the right lung has three lobes, whereas, the left lung is composed of two lobes. The branching of the primary bronchial buds are monopodial. Every secondary bronchus then undergoes progressive dichotomous branching as each branch bifurcates repeatedly. Reproducible branching in humans is completed at 16 generations in 16 weeks of gestation [12]. The last seven generations of airway are completed during the last part of gestation. Alveolization starts after 28–30 weeks in humans and is completed in postnatal period

[13]. Reid [14] presented this process in her laws of development of the human lung:
