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Congenital Diaphragmatic Hernia

diagram of congenital diaphragmatic hernia Click To Enlarge

diagram of congenital
diaphragmatic
hernia
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What is a congenital diaphragmatic hernia (CDH)?

A CDH refers to a hole in the diaphragm, the muscle that separates the chest from the abdomen. Some of the contents of the abdomen move, or herniate, through the opening into the chest cavity. As a result, the lung on the affected side is compressed by abdominal contents and is prevented from growing normally. In addition, the herniated organs cause the heart to be shifted and compress the opposite lung, although to a lesser degree. Because the effected lung is small and underdeveloped, the pulmonary blood vessels do not develop normally and lead to pulmonary hypertension (high blood pressure in the lungs) at birth. The larger the defect and the more time abdominal organs spend in the chest during gestation, the worse the underdevelopment of the fetal lungs. These changes place the baby at risk for severe breathing problems after birth.

CDH occurs in about one in every 2200 births. Approximately 85% occur on the left side and 15% occur on the right side. Babies with CDH may have problems with other developing organs such as the heart, kidneys, bowel, and brain. Additionally, a few syndromes are associated with a congenital diaphragmatic hernia. The cause of CDH is unknown. Although the overall survival of CDH in the US is 65%, survival is over 80% at the U of M.

What additional testing is recommended during the pregnancy?

A level II ultrasound is performed to confirm the diagnosis and rule out associated anomalies. A sonographic lung-to-head ratio (LHR) is used to assess the baby's lung size compared to his gestational age. This number assists the team in determining the severity of lung problems anticipated for the baby. Serial ultrasounds will be performed to monitor the baby. We recommend increased surveillance in the third trimester with ultrasound and non stress testing given the increased risk of intrauterine demise towards the end of pregnancy.

A fetal echocardiogram is recommended to assess heart structure and function. Amniocentesis is also recommended, given the higher incidence of chromosome problems.

A fetal MRI is recommended to calculate lung volumes and reliably assess the presence of liver herniation. Significant liver herniation in left sided CDH usually indicates a more severe prognosis. Lung volumes are helpful to assess the severity of the CDH.

Are there special considerations for the delivery?

Unless there is a special birth plan, a vaginal delivery is recommended and a cesarean section is reserved for obstetric indications. Delivery should be planned at a hospital that is prepared for high-risk deliveries, and that has pediatric surgical services and a neonatal intensive care unit that is able to provide ECMO (a type of heart-lung bypass machine). ECMO permits the lungs to rest while the baby receives oxygen and carbon dioxide is removed by the machine.

Is there fetal treatment for CDH?

Fetal treatment has been reserved for select few babies with severe CDH. Using a tiny fetoscope, a small detachable balloon is placed in the baby's trachea during the mid second trimester. Since the fetal lung normally produces fluid, the balloon prevents egress of this fluid which causes the small lung to expand and grow.

In severe CDH (liver herniation, a LHR < 1.0, and small lung volumes on fetal MRI), a procedure called EXIT-to-ECMO may be used at the end of pregnancy. This procedure involves a modified cesarean delivery which requires maternal general anesthesia. The baby is partially delivered but remains attached to the umbilical cord which maintains support from the placenta. A breathing tube is inserted into the baby's airway and a trial of ventilation is performed. If the baby's lungs are too small to be supported by the ventilator, then ECMO is started while the baby is still partially in the womb. The potential advantages of this procedure include avoidance of lung injury from high ventilator pressures, hemodynamic instability and normal oxygen delivery to the baby while he transitions smoothly from the womb to ECMO.

What is the treatment for CDH?

All babies with CDH are at high risk of severe respiratory problems due to the underdevelopment of the lungs. Management of respiratory failure is the first and most important step in caring for these babies. A breathing tube is immediately placed after birth to assist the baby with ventilation. A "gentle ventilation" technique is used to provide oxygen to the baby and prevent damage to the delicate lungs. A small tube is also inserted into the stomach to prevent air build up in the stomach and bowel and reduce pressure on the lungs. There are several different types of ventilators that may be used. If pulmonary hypertension is a big problem, nitric oxide may be used to relax the pulmonary arteries. The surgical repair of the CDH is delayed until the baby is stable from a heart and lung standpoint.

EMCO is a treatment option that can be implemented if the baby is not receiving enough oxygen using the "gentle ventilation" strategy. ECMO allows the lungs to rest and decreases the reactivity of the pulmonary hypertension while maintaining adequate oxygen levels for the baby. As the baby begins to improve he will be weaned from the machine as tolerated. The surgical repair may be performed during or after weaning from ECMO.

Most babies are repaired through an abdominal incision. In select stable patients, a minimally invasive thoracoscopic approach may be possible (using tiny incisions and instruments). Small diaphragmatic hernias are repaired primarily with sutures. Large defects require a prosthetic patch closure. The abdomen is smaller in CDH babies since the majority of the contents migrated into the chest cavity during fetal life. Sometimes, a temporary silo, is created on the abdominal wall to allow gradual reduction of abdominal contents over several days.

Are there any other treatment options?

The University of Michigan is the only center in the US enrolling patients in a clinical trial of Perflubron Induced Lung Growth (PILG) for babies with CDH. This study is available to babies with a left CDH who are on ECMO. Patients wishing to participate will be randomized (like flipping a coin) to either standard treatment on ECMO or PILG. The novel treatment involves filling the lungs with Perflubron (a special liquid) and placing this liquid under constant pressure to stimulate the lungs to grow. A previous study in babies with CDH from the University of Michigan showed that this strategy is safe and may cause the small lungs to grow and improve overall outcome.

Are there other health problems that are more common among babies with CDH?

Many babies with CDH will have long-term health issues of varying degree. The extent of long-term problems is usually related to the severity of the CDH and neonatal illness.

Lung problems may include the inability to wean off the ventilator, the need for supplemental oxygen, chronic lung disease, persistent pulmonary hypertension and asthma. Feeding difficulties are common, and many babies need supplemental feeding through a tiny tube in their nose or a gastrostomy tube (a feeding tube placed into the stomach). Despite supplemental feeding, some babies still have a difficult time gaining weight, especially in the first year of life.

Gastroesphogeal reflux or "heartburn" is common in babies with CDH and often treated effectively with medicine. However, some babies may require a separate operation (Nissen fundoplication) to treat the reflux. Potential neurological problems include hearing loss, and developmental delay, and occasionally more serious neurological problems. These risks are greatest in children requiring ECMO support. Some patients develop scoliosis.

Close follow-up by a team of specialists is essential to manage the long-term health issues in CDH.

Can this happen again with another pregnancy?

The risk of CDH occurring in another pregnancy is rare. The majority of CDH cases are random (sporadic) events. The chance this could happened again is thought to be approximately 2%. If the CDH is part of a genetic syndrome or chromosomal anomaly, the chance of recurrence is dependent on the recurrence risk of the underlying syndrome or genetic change. Prenatal diagnostic testing may be available in future pregnancies if a genetic cause is identified. Your doctor and a genetic counselor will review the risk in your family.

CDH Survival Calculator

This survival calculator was developed in Microsoft Excel 2002 with Service Pack 3. It has not been tested in other Excel versions but will likely run in most instances. In order to use this instrument, your copy of Excel must be able to run macros. In some institutions, IT may have disabled this functionality altogether or may have set Excel to ask you upon opening if you'd like to enable macros. If asked, say yes.

If you are unable to run the application and your IT support is unable to assist, an explicit solution to the statistical model to allow calculation of risk are available from the authors.

Lastly, we ask that any use of this calculator for research purposes that result in publication acknowledge its authorship.

CDH Survival Calculator