CONGENITAL DIAPHRAGMATIC HERNIA BOCHDALEK

Congenital Diaphragmatic Hernia (Bochdalek) : The most common congenital diaphragmatic hernia (CDH) is that which occurs through the posterolateral defect of Bochdalek. It is caused by failure of the pleuroperitoneal membrane to develop adequately and close before the intestines returning to the abdomen at the tenth week of gestation. The intestines then enter the pleural cavity and cause poor lung development leading to pulmonary hypoplasia (a reduced number of alveoli per area of lung tissue). This defect is postero-lateral in the diaphragm and may vary in size. Stomach, liver or spleen may be partly in chest as well. Frequency is 1:2000 live births and the natural history in prenatally
diagnosed congenital diaphragmatic hernia is that 60% will die.

The clinical presentation is that the newborn becomes rapidly cyanotic, acidotic, and has poor ventilation. Major findings relate to the degree of pulmonary maldevelopment. Chest films will show intestines in the chest. Left sided hernias are more common than right (90% on left). Placement
of a radiopaque nasogastric tube may show the tube coiled in the lower left chest.

Higher risk factors are: early appearance of symptoms in life, prematurity and associated anomalies. Treatment consist of rapid intubation and ventilation with use of muscle relaxants, placement of a nasogastric tube to prevent gaseous distension of the intestines and preoperative stabilization of arterial blood gases and acid-base status.

Surgery can be undertaken when one of the following objectives are met:
(1) blood gases normalize with no significant changes between preductal and postductal samples,
(2) echocardiogram demonstrate reduce pulmonary pressure and pulmonary peripheral resistance.

Operative management consist of abdominal approach, closure of hernia by primary repair or use of
mesh, and correction of malrotation. Postoperative management is very difficult. Due to hypoplastic lungs, there is frequently pulmonary hypertension leading to right-to-left shunting and progressive hypoxemia, hypercarbia, and acidosis that worsens the pulmonary hypertension. The use of chest tubes may cause overstretching of the already hypoplastic alveoli causing: increase pulmonary hypertension, reduce functional residual capacity and reduce lung compliance. Postoperatively, the infant should be kept paralyzed and ventilated and only very slowly weaned from the ventilator. The severity of pulmonary hypoplasia, both ipsilaterally and contralaterally, is the main determinant of outcome.

ECMO (extracorporeal membrane oxygenator) has come to reduce somewhat the mortality of this condition. The mortality of congenital diaphragmatic hernia is directly related to the degree of lung hypoplasia associated. Death is caused by persistent pulmonary hypertension and right ventricular failure. Prospective studies of prenatally diagnosed fetus prior to 25 wk. gestation has shown that 60% will die despite optimal postnatal care. This unsolved problem has prompted investigators to develop new treatment options such as preoperative stabilization, jetfrequency ventilation, and ECMO. Another area of development is intrauterine fetal surgical repair.

To achieve success fetal surgery should:
(1) pose no risk to the mother (innocent bystander) or her future reproductive capacity;
(2) tocolytic therapy in the post-op weeks should proved effective to avoid prenatal stillbirths; and
(3) the procedure should be superior to conventional therapy. Intrauterine repair has meet with limited success due to herniation of the fetal liver into the chest through the defect. Disturbance of the umbilical circulation during or after liver reduction causes fetal death. Positive-pressure ventilation after birth reduces the liver before the baby comes for surgical repair. Dr. Harrison (USFC Fetal Treatment Center) has devised separate fetal thoraco-abdominal incisions to deal with this problem ("two-step dance"), reducing or amputating the left lateral segment of the liver. Another less invasive approach is enlarging the hypoplastic lungs by reducing the normal egress of fetal lung fluid with controlled tracheal obstruction called PLUGS (Plug Lung Until it Grows).

Delayed presentation beyond the neonatal period is rare, estimated to occur in 4-6% of cases. Infants
and children will present with either respiratory or gastrointestinal symptoms such as: chronic respiratory tract infection, vomiting, intermittent intestinal obstruction, and feeding difficulty. Occasionally the child is asymptomatic. The small size of the defect protected by either the spleen or the liver and the presence of a hernial sac may delay the intestinal herniation into the chest. A rise intraabdominal pressure by coughing or vomiting transmitted to any defect of the diaphragm makes visceral herniation more likely. Diagnosis is confirmed by chest or gastrointestinal contrast imaging. Management consists of immediate surgery after preop stabilization. Most defects can be closed primarily through an abdominal approach. Chest-tube placement in the non-hypoplastic lung is of help. Surgical results are generally excellent. A few deaths have resulted from cardiovascular and respiratory compromise due to visceral herniation causing mediastinal and pulmonary compression.