Pediatric Surgeon Explains Congenital Diaphragmatic Hernia (CDH)
CDH affects 1 in 5,000 live births
Just want to stress the importance of referral to high risk perinatologists and pediatric surgeons early in the pregnancy for counseling and management to minimize complications and improve survival.
Congenital diaphragmatic hernia (CDH) is a congenital abnormality that affects 1 in 5,000 live births, resulting in a partial absence of a portion of the diaphragm associated with variable degrees of lung underdevelopment.
As a tertiary referral center for this anomaly, Cook Children's cares for approximately 20 cases per year.
Most commonly the left side of the diaphragm is affected, called a Bochdalek hernia, resulting in herniation of the stomach, spleen, portions of the small and large intestine, and less commonly the liver into the chest cavity.
Most Bochdalek type CDH are identified prenatally during routine fetal ultrasound studies. Once identified, expecting mothers should be referred to a high risk perinatologist and pediatric surgeon for monitoring and counseling as many of these newborns will be born prematurely and require specialized neonatology and pediatric surgical care after birth.
The referral to high risk perinatologists and pediatric surgeons is extremely important early in the pregnancy for counseling and management to minimize complications and improve survival.
If the right side of the diaphragm is affected, usually the liver blocks most of the abdomen organs from herniating into the chest cavity. The lung on the same side of the body is typically small in size, but both lungs are developmentally abnormal in most cases.
A less common type of CDH is called a Morgagni hernia, in which the diaphragm defect is located just behind the sternum. This type usually does not present until later in childhood and often found incidentally during evaluation of breathing or gastrointestinal complaints. These usually do not have associated lung developmental abnormalities.
Interestingly, management of the abnormal lung function takes precedence over repair of the diaphragm defect. Often it’s difficult to predict the severity of lung dysfunction simply based upon the size of the hernia defect.
Much study has gone into prenatal prediction of lung function, using different parameters measured from ultrasound or MRI studies of the fetus in the womb. Lung to head ratios are one such measurement to determine the degree of lung development and outcome, but this measurement has not uniformly been associated with worse outcome.
Presence of the liver herniating into the chest has been pretty consistent with worse outcome, but many of these infants still can survive and do well. The diaphragm defect is repaired once the lung function has stabilized and it is safe to proceed with surgery. This may take several days and sometimes weeks with Bochdalek type CDH.
Sometimes enough of the diaphragm remains to sew the pieces back together directly, but frequently not enough muscle remains and a synthetic mesh patch must be used to replace the missing tissue. Most Bochdalek CDH surgeries are conducted from the abdomen side of the diaphragm, but these can be repaired through the chest as well.
Laparoscopy, or the use of small cameras and instruments placed through small cuts, can be used in selected patients with good lung function from either the abdomen or chest. Morgagni type hernias are more suited for laparoscopic repair from the abdomen, and infrequently a mesh is required.
ECMO, or extracorporal membranous oxygenation, is essentially partial or total lung and heart bypass. Infants usually have large tubes placed into their neck artery and vein on the right side and their blood is circulated through a machine that adds oxygen and removes carbon dioxide from the blood. This treatment is reserved for the sickest infants whose lung function cannot be supported by special mechanical ventilation strategies and medications. Up to 45 percent of infants will require ECMO, and that number has improved in the last decade with better lung management strategies.
Once lung function improves, the infant is weaned off ECMO back to other mechanical ventilation modalities. We try to reserve repair of the CDH until after ECMO has been successfully weaned to minimize complications from the surgery. A very small number of infants will not be able to wean effectively off ECMO and we will fix the defect while on ECMO in hopes that removing the lung compression from the herniated abdomen organs will improve lung function enough to get off ECMO after surgery. Some surgeons advocate for earlier repair of the CDH defect while on ECMO, but this approach is still controversial.
We have begun to use less invasive approaches to placement of the ECMO circuit in select patients who only require lung bypass and not heart bypass. This potentially minimizes damage to the neck vessels and preserves their function later in life.
Surgery is performed in a delayed fashion to allow lung function to improve, but usually in the first few weeks of life. Morgagni type CDH is not repaired until it is identified, usually in the elementary school years.
Bochdalek hernias, which account for up to 98 percent of CDH, still carry approximately a 10-20 percent mortality. Those infants who require ECMO have a worse outcome, and as many as 40 percent of those infants will not survive
Infants who survive and do not have other life-altering congenital anomalies can have a normal life with normal lung development. All infants with Bochdalek CDH have intestinal malrotation. Lung development continues until around age 2. Fifty percent of infants will have associated abnormalities, but most are not life-threatening. These include:
- Tracheobronchial anomalies
- Down Syndrome
- Trisomy 13 and Trisomy 18
I think most families are surprised to learn that fixing the hole in the diaphragm and removing the abdomen organs from the chest does not affect the lung function much. We are often asked why we don’t proceed immediately to the operating room, because I think it is rational for families to assume the compression of the lungs is the main culprit for lung dysfunction.
In reality, it is the degree of lung underdevelopment and not compression that causes the breathing difficulty and ultimately decides the outcome. Also, experts in CDH do not believe the lung development problem is related to the hernia and compression, but it seems the hernia and lung development likely occurs simultaneously from processes that affect both structures. The true cause is yet undefined.
About the Author
Chad Hamner, M.D.,is the Medical Director for Pediatric Trauma Services and Co-Medical Director Pediatric Critical Care Services at Cook Children's. He is currently board-certified in general surgery, surgical critical care and pediatric surgery from the American Board of Surgery and is a fellow of the American College of Surgeons. Dr. Hamner has been practicing surgery for 10 years and his clinical focus is pediatric surgery and critical care.