Congenital diaphragmatic hernia is essentially a defect in the diaphragm that occurs in the uterus. The disorder results in lung hypoplasia, pulmonary hypertension and severe hypoxia. Many of these infants have associated congenital defects which increase the morbidity and mortality.
The diagnosis of congenital diaphragmatic hernia is often made prenatally using ultrasound. Infants with diaphragmatic hernia may also have other problems that may be identified with ultrasound like polyhydramnios, absent gastric bubble, mediastinal shift, and hydrops fetalis. Ultrasound may also show intestinal contents in the chest cavity and even a mediastinal shift. It is important to remember that there are other disorders that may mimic these findings, such as pulmonary sequestration, congenital cystic adenomatoid malformation, foregut cysts and mediastinal cysts.
Infants born with diaphragmatic hernia may present with clinical symptoms which might be due to pulmonary hypoplasia and the herniation of intestinal contents into the chest. The infant will usually present with
The physical exam can reveal a scaphoid abdomen and auscultation might reveal absent breath sound in the chest. Bowel sounds may also be heard in the chest and the heart sounds may be absent or displaced.
Some infants with a mild diaphragmatic defect may present late with features like respiratory distress, signs of bowel obstruction, metabolic acidosis or necrotic bowel.
Timing of Surgery
No time for repair of congenital diaphragmatic hernia (CDH) is ideal, but the pediatric surgeons suggest that the window of opportunity is 24-48 hours after birth. This time period allows for stabilization of the infant and helps achieve normal pulmonary arterial pressures with use of nitric oxide. It also gives time to correct any metabolic or electrolyte deficiency.
When a diaphragmatic hernia is visualized on ultrasound, amniocentesis can be done to assess the karyotype. In addition, maternal serum alpha fetoprotein levels may be diminished.
After birth the following workups are required:
A repetition of ultrasound is required at birth to confirm the diagnosis of diaphragmatic hernia
Echo is required to assess for presence of congenital heart defects and presence of any shunts. Common heart defects present include atrial and ventricular septal defects or a ductus arteriosus. These heart defects need to be repaired first prior to the diaphragmatic repair. In most centers, interventional endovascular procedures can now close most of these congenital heart defects. Serial echo are required as infants with diaphragmatic hernia may develop pulmonary hypertension. Hence measurement of pulmonary artery pressures and responsive to treatment is necessary. All infants with a diaphragmatic hernia need serial ECHOs to determine the pulmonary artery pressures and response to treatment. Detailed ultrasound can also assess the degree of pulmonary hypoplasia.
Chest x-ray is often the first imaging study done to confirm presence of diaphragmatic hernia. It may show a mediastinal shift to the contralateral side, bowel loops in the chest, or the presence of tip of the nasogastric tube in the chest cavity. Hernias on the right side are often difficult to visualize because the liver often prevents bowel contents from entering the chest cavity. Sometimes the liver may be pushed in the right chest cavity and may appear as a lobar consolidation or diaphragmatic eventration.
Over the years, many studies have looked at survival rates in infants with diaphragmatic hernia. Survival of infants with diaphragmatic hernia depends on comorbidity, degree of prematurity, and extent of hypoxia . For infants with just a diaphragmatic defect, the prognosis is good. Infants with lung hypoplasia and pulmonary hypertension tend to have a poor prognosis. Even with the use of ECMO and high frequency jet ventilation, the mortality rates remain high. Post operative complications are serious and include bowel obstruction, adhesions, volvulus and leakage of peritoneal fluid into the chest cavity. Most infants have a prolonged hospital stay and later require extensive pulmonary rehabilitation. Studies have shown persistent neuropsychiatric deficits in a number of children who had congenital diaphragmatic hernia at birth.
The exact cause of congenital diaphragmatic hernia remains unknown. There are several hypothesis as to why diaphragmatic hernias develop. Infants with a variety of chromosomal abnormalities are known to develop diaphragmatic hernia. However, there is no particular syndrome which has a high incidence of diaphragmatic hernia and the incidence varies. Diaphragmatic hernias are not genetically inherited, as the familial incidence is very low.
The role of toxins, environmental chemicals and drugs as a cause of diaphragmatic hernia is uncertain. There is no one study that has shown a solid correlation between exposure to these agents and the occurrence of the hernia. However, certain drugs like thalidomide, quinine and nitrogen have been used to induce diaphragmatic defects in laboratory animals.
The diaphragmatic hernia results because of the failure of the pleuroperitoneal canals to close. When this canal remains open, the intestine and other intra-abdominal organs can enter the chest cavity. As these structures occupy volume, they compress the lung at a critical stage during its maturation, leading to hypoplasia. There is also a shift of the mediastinum to the contralateral chest cavity that may result in mild compression of the contralateral lung and the heart.
Congenital diaphragmatic hernia is not a common disorder and occurs in 0.1 per 300 live births. The disorder is known to occur in both genders and all races. Outside the USA, the exact number of infants with this disorder is not known but the rates are felt to be similar. The majority of these infants are treated in specialized tertiary care centers where ECMO and high frequency jet ventilation techniques are available.
The pathophysiology of a congenital diaphragmatic hernia is related to several associated factors like pulmonary hypertension, pulmonary hypoplasia, absence of surfactant and immaturity of the lung. The basic pathology starts with the intestinal contents herniating into the chest cavity. The compression effect of intestine and the other intra-abdominal organs prevent lung development on the ipsilateral side. The sooner the herniation occurs in the chest cavity, the more pronounced is the pathology on the lung. Lung development and airway division can be inhibited by the compressive effects of bowel. Besides effecting lung development, the herniation of the intestine also affect development of the pulmonary arterial system and bronchi, and the end result is fewer pulmonary artery branches. The eventual outcome is development of severe muscular hypertrophy of the pulmonary vessels that are sensitive to vasoconstriction. Pulmonary hypertension that results often leads to right to left shunting at the ductal and through the foramen ovale, resulting in cyanosis. The persistence of this fetal circulation leads to severe right heart strain leading to hypoxemia, hypercarbia, acidosis and pulmonary hypertension. Infants with congenital diaphragmatic hernia also have deficiency of surfactant and impairment of antioxidant enzymes making the lung parenchyma susceptible to hypoxic injury. Depending on the extent of intestinal herniation in the chest cavity, there is a shift of the mediastinum to the contralateral side and compression on the heart.
Because the cause of diaphragmatic hernia is unknown, prevention is difficult. However, all pregnant females should undergo regular prenatal ultrasounds, so that the disorder can be identified early and preparations can be made for transfer to a tertiary care center. The patient should be told to avoid use of medications, herbal products and any other unknown agent during the pregnancy, without first speaking to the physician. Because congenital diaphragmatic hernia does not appear to have a genetic link, the risk to successive pregnancies is low.
Congenital diaphragmatic hernia is not a novel disorder. The first case was reported nearly 400 years ago. The first surgical attempt to repair this disorder was done about 140 years ago, but at that time there was no anesthesia and the surgical equipment were crude, hence mortality rates were high. Over the years, there has been a better understanding of congenital diaphragmatic hernia and its pathophysiology. The condition is diagnosed in utero in most cases and the mother is often transferred to a tertiary care center for post natal care. The presentation of an infant with a diaphragmatic hernia can vary depending on when the defect developed in-utero, the degree of hypoxia, presence of pulmonary hypertension and any other co-morbidities. Congenital diaphragmatic hernia is often associated with other anomalies at birth that increase the morbidity and mortality. Congenital heart defects, renal anomalies, chromosomal defects, urological abnormalities and neural tube defects tend to occur in at least 10-15% of infants.
In the past immediate surgery was undertaken for infants with congenital diaphragmatic hernia, but now with better a understanding, most experts indicate that surgery should be deferred until the infant is stabilized. Most of these infants require immediate intubation, with low ventilatory pressures and nitric oxide. In some centers high frequency jet ventilation and extra corporeal membrane circulation (ECMO) have been used to help infants overcome the hypoxia and pulmonary hypertension .
Congenital diaphragmatic hernia is a serious disorder where there is a defect in the diaphragm during fetal development. The abdominal contents can then enter the chest cavity and prevent lung development on that side. In addition, the intestines can push the chest contents to the opposite site and also compress the heart. Infants are usually diagnosed with diaphragmatic hernia at birth and transferred to a specialized center. Most infants are symptomatic and require intubation with ventilation. Surgery is often done within 24-48 hours. Because of the failure of the lung to develop, most infants develop high pressures in their lung which prevents oxygenation. Right sided heart failure can occur. The prognosis of these infants depends on the complexity of the diaphragmatic defects and other comorbid disorders. Despite availability of new tools, the treatment of diaphragmatic hernia is difficult and does carry a high mortality.
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