History
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.
Physical
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.
Causes
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. [10]
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 13, trisomy 18, trisomy 21, 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. [11]
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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.
