A failure of development of the posterolateral parts of the diaphragm at the Bochdalek foramen or retrosternally at the Morgagni foramen allows herniation of the gut into the chest cavity. Left-sided Bochdalek hernias are more common than those on the right. The defect occurs in one out of 2200 births. Associated anomalies with diaphragmatic hernias include congenital heart diseases, genitourinary anomalies, gastrointestinal anomalies, hydronephrosis, and cystic kidneys. Frequently the lungs are hypoplastic bilaterally and have abdominal pulmonary vasculature, predisposing the infant to pulmonary hypertension.
Fifty percent of fetuses with diaphragmatic hernia have difficulty swallowing, and the condition is therefore associated with polyhydramnios. The diagnosis can often be made by prenatal ultrasonography.
CLINICAL FEATURES The clinical findings are localized to the respiratory and digestive tracts. The chest is large, while the abdomen is scaphoid. Bowel sounds are heard in the left chest, and the heart is displaced to the right. Dyspnea, cyanosis, retractions, and vomiting are proportional to the amount of abdominal viscera herniated into the thorax. Radiologic study reveals air-filled loops of bowel in the chest cavity and an absent diaphragmatic margin. The heart is often displaced and the lungs are small in size.
TREATMENT Immediate surgical repair is a method of treatment, and the neonate should be stabilized as much as possible prior to surgery. Alternatively, the neonate can be placed on extracorporeal membrane oxygenation (ECMO) prior to repair. The infant should be intubated immediately, and little or no attempt should be made to ventilate with a mask. The endotracheal tube should be positioned above the carina. Rapid ventilatory rates and low peak inspirator pressures are used to ventilate the infant and prevent reactive respiratory acidosis and hypercarbia, which are potentially conducive to the development of pulmonary hypertension. A large-caliber 10F tube should be placed in the stomach with low continuous suction applied. An umbilical artery catheter is useful to monitor blood gases and pH. Any acidemia should be corrected and the pH maintained in the alkalotic range (pH > 7.45) if possible. Intravenous fluids should be given and the patient kept warm.
The outcome of management of diaphragmatic hernia is dependent on pulmonary parenchymal and vascular hypoplasia, as well as the complex syndrome of persistent fetal circulation. The morbidity is higher when the symptoms present at birth and when the diaphragmatic hernia is detected prenatally. Morgagni hernias, if they do not affect cardiac output, generally have a better prognosis than do Bochdalek hernias. Common complications that occur pre- and postoperatively are pneumothorax, persistent fetal circulation, overdistension of hypoplastic lungs, and chylothorax. The recent introduction of the use of ECMO for infants with persistent pulmonary hypertension after hernia repair has made a minimal impact on prognosis.
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