CONGENITAL DIAPHRAGMATIC HERNIA

Congenital Diaphragmatic Hernia
The topic of congenital diaphragmatic hernia (CDH) frequently appears in the medical literature since its first description in the early 18th century. Initial theories about the pathophysiology of this condition centered on the presence of the herniated viscera within the chest and the need for its prompt removal. In 1946, Gross reported the first successful repair of a neonatal diaphragmatic hernia in the first 24 hours of life. The medical literature for the next decade addressed CDH as a surgical problem and discussed various technical aspects of surgical repair, including techniques required to close large defects. In the 1960s, however, Areechon and Reid observed that the high mortality rate of CDH was related to the degree of pulmonary hypoplasia at birth. Over the past 20 years, pulmonary hypertension and pulmonary hypoplasia have been recognized as the 2 cornerstones of the pathophysiology of CDH. In recent years, evidence suggests that dysfunction of the surfactant system as well as cardiac maldevelopment may further complicate the pathophysiology of CDH.

congenital diaphragmatic hernia pathophysiology: The 3 basic types of CDH are 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 90% of cases. Left-sided hernias allow herniation of both small and large bowel as well as intra-abdominal solid organs into the thoracic cavity. In right-sided hernias, only the liver and a portion of the large bowel tend to herniate. Bilateral hernias are uncommon and usually fatal.

CDH is characterized by a variable degree of pulmonary hypoplasia associated with a decrease in cross-sectional area of the pulmonary vasculature and dysfunction 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 intra-acinar 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 frequency: Internationally: CDH occurs in 1 of every 2000-4000 live births and accounts for 8% of all major congenital anomalies. The risk of recurrence of isolated CDH for future siblings is approximately 2%. Familial CDH rarely occurs and may be due to a multifactorial/threshold inheritance pattern or, in some cases, an autosomal recessive pattern. CDH can also occur as a part of Fryns syndrome, an autosomal recessive disorder with variable features, including diaphragmatic hernia, cleft lip or palate, and distal digital hypoplasia.

congenital diaphragmatic hernia Mortality/Morbidity:
• Mortality is difficult to determine. This is partially because of the hidden mortality for this condition. Hidden mortality refers to infants with CDH who are so severely affected that they die prior to transfer to a surgical site. This bias may be especially important when evaluating institutional reports of outcome.
• Population-based studies report survival rates ranging from 25-60%. Infants with multiple anomalies have much lower survival rates than those with isolated defects.

Sex: Most studies report a male preponderance for isolated posterolateral CDH (male-to-female ratio of approximately 1.5:1).

Age:
• While CDH is most commonly a disorder of the newborn period, as many as 10% of patients may present after the newborn period and even during adulthood.
• Outcome in patients with late presentation of CDH is extremely good, with low or no mortality.

congenital diaphragmatic hernia history:
• Infants may have an antenatal history of polyhydramnios.
• Infants most commonly present with a history of cyanosis and respiratory distress in the first minutes or hours of life, although a later presentation is possible.

congenital diaphragmatic hernia physical:
• Frequently, infants exhibit a scaphoid abdomen, respiratory distress, and cyanosis.
• 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.

congenital diaphragmatic hernia causes:
• The cause of CDH is largely unknown. No single gene mutation has been identified as producing or contributing to this anomaly.
• Posterolateral hernia may occur as an isolated defect or in association with other congenital anomalies. CDH can occur as part of a multiple malformation syndrome in up to 40% of infants, principally with cardiovascular, genitourinary, and gastrointestinal malformations. Lethal anomalies are present in up to 16% of infants.
• Karyotype abnormalities have been reported in 4% of infants with CDH, and CDH may be found in a variety of chromosomal anomalies including trisomy 13, trisomy 18, and tetrasomy 12p mosaicism. CDH may be associated with nonchromosomal disorders such as the de Lange syndrome.
• Retrosternal hernias are also associated with cardiovascular, genitourinary, and gastrointestinal malformation.

congenital diaphragmatic hernia Lab Studies:
• Arterial blood gas
o Obtain frequent arterial blood gas (ABG) measurements to assess for pH, PaCO2, and PaO2.
o Note the sampling site because persistent pulmonary hypertension (PPHN) with right-to-left ductal shunting often complicates CDH. The PaO2 may be higher from a preductal (right-hand) sampling site.

• Chromosome studies
o Obtain chromosome studies because of the frequent association with chromosomal anomalies.
o In rare cases, chromosomal disorders that can only be diagnosed by skin biopsy may be present. If dysmorphic features are observed on examination, a consultation with a geneticist is often helpful.

• Serum electrolytes: Monitor serum electrolytes, ionized calcium, and glucose levels initially and frequently. Maintenance of reference range glucose levels and calcium homeostasis is particularly important.

congenital diaphragmatic hernia Imaging Studies:
• Chest radiography o Obtain a chest radiograph if CDH is suspected.
o Placement of an orogastric tube prior to the study helps determine the position of the stomach.
o Typical findings in left-sided posterolateral CDH include air- or fluid-filled loops of the bowel in the left hemithorax and shift of the cardiac silhouette to the right.
o Examine the chest radiograph for evidence of pneumothorax.

• Cardiac ultrasonography
o Perform ultrasonographic studies to rule out congenital heart diseases.
o Because the incidence of associated cardiac anomalies is high (up to 25%), cardiac ultrasonography is needed to evaluate for associated cardiac anomalies.

• Renal ultrasonography: A renal ultrasonographic examination may be needed to rule out genitourinary anomalies.

• Cranial ultrasonography
o Perform cranial sonography if the infant is being considered for extracorporeal support.
o Ultrasonographic examination should focus on evaluation of intraventricular bleeding and peripheral areas of hemorrhage or infarct or intracranial anomalies.

congenital diaphragmatic hernia Other Tests: Pulse oximetry
o Continuous pulse oximetry is valuable in the diagnosis and management of PPHN.
o Place oximeter probes at preductal (right-hand) and postductal (either foot) sites to assess for a right-to-left shunt at the level of the ductus arteriosus.

congenital diaphragmatic hernia procedures:
• Intubation and mechanical ventilation
o Endotracheal intubation and mechanical ventilation are required for all infants with severe CDH who present in the first hours of life.
o Avoid bag-and-mask ventilation in the delivery room because the stomach and intestines become distended with air and further compromise pulmonary function.
o Avoid high peak inspiratory pressures and overdistension. Consider high-frequency ventilation if high peak inspiratory pressures are required.

• Arterial catheter placement: Place an indwelling catheter in the umbilical artery or in a peripheral artery (radial, posterior tibial) for frequent ABG monitoring.

• Central venous catheter placement
o Place a venous catheter via the umbilical or femoral vein to allow for administration of inotropic agents and hypertonic solutions such as calcium gluconate.
o Frequently, placing an umbilical venous catheter is difficult because of the altered position of the heart and liver. For the same reason, confirming correct position (in the low right atrium) can be difficult, and ultrasonography may be needed.

congenital diaphragmatic hernia Histologic Findings: Both lungs appear abnormal, although histologic changes are more severe on the affected side. Bronchi are less numerous, and the overall number of alveoli is reduced. In addition, the lungs appear to be less mature with fewer mature alveoli. Pulmonary vascular abnormalities occur in addition to parenchymal abnormalities. These vascular abnormalities are characterized by both a reduction in the cross-sectional area of the pulmonary vascular bed and an abnormal increase in muscularization of pulmonary arteries and arterioles.