Congenital diaphragmatic hernia (see the image below) is characterized by a variable degree of pulmonary hypoplasia associated with a decrease in cross-sectional area of the pulmonary vasculature and alterations of the surfactant system. There are 3 basic types of congenital diaphragmatic hernia: the posterolateral Bochdalek hernia (occurring at approximately 6 weeks' gestation), the anterior Morgagni hernia, and the hiatus hernia.
Radiograph of a 1-day-old infant with a moderate-sized congenital diaphragmatic hernia (CDH). Note the air- and fluid-filled bowel loops in the left chest, the moderate shift of the mediastinum into the right chest, and the position of the orogastric tube.
Signs and symptoms
Infants with congenital diaphragmatic hernias most commonly present with respiratory distress and cyanosis in the first minutes or hours of life, although a later presentation is possible. The respiratory distress can be severe and may be associated with circulatory insufficiency, requiring aggressive resuscitative measures.
The 3 basic types of congenital diaphragmatic hernia include the posterolateral Bochdalek hernia (occurring at approximately 6 weeks' gestation), the anterior Morgagni hernia, and the hiatus hernia. The left-sided Bochdalek hernia occurs in approximately 85% of cases. Left-sided hernias allow herniation of both the small and large bowel and intraabdominal solid organs into the thoracic cavity. In right-sided hernias (13% of cases), only the liver and a portion of the large bowel tend to herniate. Bilateral hernias are uncommon and are usually fatal.
Congenital diaphragmatic hernia is characterized by a variable degree of pulmonary hypoplasia associated with a decrease in cross-sectional area of the pulmonary vasculature and alterations of the surfactant system. The lungs have a small alveolar capillary membrane for gas exchange, which may be further decreased by surfactant dysfunction. In addition to parenchymal disease, increased muscularization of the intraacinar pulmonary arteries appears to occur. In very severe cases, left ventricular hypoplasia is observed. Pulmonary capillary blood flow is decreased because of the small cross-sectional area of the pulmonary vascular bed, and flow may be further decreased by abnormal pulmonary vasoconstriction.
Congenital diaphragmatic hernia occurs in 1 of every 2000-3000 live births and accounts for 8% of all major congenital anomalies. The risk of recurrence of isolated (ie, nonsyndromic) congenital diaphragmatic hernia in future siblings is approximately 2%. Familial congenital diaphragmatic hernia is rare (< 2% of all cases), and both autosomal recessive and autosomal dominant patterns of inheritance have been reported. Congenital diaphragmatic hernia is a recognized finding in Cornelia de Lange syndrome and also occurs as a prominent feature of Fryns syndrome, an autosomal recessive disorder with variable features, including diaphragmatic hernia, cleft lip or palate, and distal digital hypoplasia.
Mortality has traditionally been difficult to determine. This is partially because of the "hidden mortality" for this condition, which refers to infants with congenital diaphragmatic hernia who die in utero or shortly after birth, prior to transfer to a surgical site. This bias may be especially important when evaluating institutional reports of outcome.
A population-based study from Western Australia indicated that only 61% of infants with congenital diaphragmatic hernia are live born. In that study, nearly 33% of pregnancies that involved a fetus with congenital diaphragmatic hernia were electively terminated. Most of the pregnancies (71%) were terminated because of the presence of another major anomaly.
Mortality after live birth is generally reported to range from 40-62%, and some authors argue that the true mortality of congenital diaphragmatic hernia has not changed with introduction of new therapies. The presence of associated anomalies has consistently been associated with decreased survival; other associations with poor outcome include prenatal diagnosis, prematurity, low birth weight, and early pneumothorax.
As noted in Mortality/Morbidity, population-based studies show that congenital diaphragmatic hernia (CDH) is diagnosed based on prenatal ultrasonography findings in approximately one half of affected infants. Infants may have a prenatal history of polyhydramnios.
Infants most commonly present with respiratory distress and cyanosis in the first minutes or hours of life, although a later presentation is possible. The respiratory distress can be severe and may be associated with circulatory insufficiency, requiring aggressive resuscitative measures.
Infants frequently exhibit a scaphoid abdomen, barrel-shaped chest, and signs of respiratory distress (retractions, cyanosis, grunting respirations).
In left-sided posterolateral hernia, auscultation of the lungs reveals poor air entry on the left, with a shift of cardiac sounds over the right chest. In patients with severe defects, signs of pneumothorax (poor air entry, poor perfusion) may also be found.
Associated anomalies occur in a relatively high percentage of infants. Dysmorphisms such as craniofacial, extremity abnormalities, or spinal dysraphism may suggest syndromic congenital diaphragmatic hernia.
The diaphragm initially develops as a septum between the heart and liver, progresses posterolaterally, and closes at the left Bochdalek foramen at approximately 8-10 weeks' gestation.
The herniation of viscera in severe congenital diaphragmatic hernia is believed to occur during the pseudoglandular stage of lung development. Lung compression results in pulmonary hypoplasia that is most severe on the ipsilateral side, although both lungs may be abnormal. Pulmonary hypoplasia is associated with fewer bronchial generations, alveoli, and arterial generations.
Congenital diaphragmatic hernia can be induced in rat models with administration of the herbicide toxin nitrofen. Studies in these models show that the diaphragmatic defect occurs in the initial stages of diaphragm development, rather than in the later stages.
Fetal exposure to nitrofen causes a variable amount of lung hypoplasia. The fact that only 60-90% of exposed rat pups demonstrate diaphragmatic defects suggests a “dual-hit” hypothesis, in which 2 insults (one primarily affecting the lungs and another primarily affecting diaphragm development) contribute to the pathophysiology of congenital diaphragmatic hernia.
Congenital diaphragmatic hernia may occur as a nonsyndromic or isolated defect. Less than 2% of such cases are estimated to be familial. Pedigrees consistent with autosomal recessive, autosomal dominant, and X-linked inheritance patterns have been described.
More than 10% of infants with congenital diaphragmatic hernia have an underlying syndromic diagnosis, although few gene mutations are currently recognized. Congenital diaphragmatic hernia is a recognized finding of Cornelia de Lange syndrome, an autosomal dominant syndrome with characteristic facial features, hirsutism, and developmental delay. Fryns syndrome is an autosomal recessive condition that includes congenital diaphragmatic hernia as the cardinal feature, along with hypoplasia of the distal digits and other variable abnormalities of the brain, heart, and genitourinary development. An associated gene has not yet been identified, and the prognosis of Fryns syndrome is poor.
Chromosome abnormalities have been reported in as many as 30% of infants with congenital diaphragmatic hernia, which has been described as part of trisomy , trisomy , trisomy , and Turner syndrome (monosomy X). Pallister-Killian syndrome (tetrasomy 12p mosaicism) presents with findings that are similar to those of Fryns syndrome, including coarse facial features, aortic stenosis, cardiac septal defects, and abnormal genitalia. This diagnosis can only be made if a karyotype is determined based on skin biopsy findings.
Chromosome deletions on chromosomes 1q, 8p, and 15q have been reported in association with congenital diaphragmatic hernia. Deletions of chromosomes 8p and 15q appear to be associated with heart malformations.
Deficiencies in vitamin A availability, metabolism, and signaling have been found to contribute to the development of congenital diaphragmatic hernia in animal models and may also be relevant in human fetal development
Last edited by Medical Photos; 09-02-2015 at 05:26 PM.
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