What is a Congenital Diaphragmatic Hernia (CDH)?
The diaphragm is the breathing muscle that separates the chest cavity and the abdominal cavity. The diaphragm develops when the fetus is about two months old. Congenital Diaphragmatic Hernia (CDH) is the absence of the diaphragm, or a hole in the diaphragm, at birth. This can occur on either the left or right side, but is most common on the left.
The contents of the abdomen, including the stomach, intestines, liver and spleen, may go through the hole and into the chest. The contents prevent the normal development of the lung (pulmonary hypoplasia) on that side, and may affect the growth of the other lung. After birth the infant will have difficulty breathing if the lungs are not developed enough.
There are two types of diaphragmatic hernia:
- Bochdalek hernia: This type involves an opening on the back side of the diaphragm. The stomach, intestines and liver or spleen usually move up into the chest cavity.
- Morgagni hernia: This type is rare and involves an opening in the front of the diaphragm, just behind the breast bone. The liver or intestines may move up into the chest cavity.
What causes CDH?
As a fetus grows in its mother’s uterus before birth, different organ systems are developing and maturing. The diaphragm forms between the 7th and 10th week of pregnancy. The esophagus (the tube that leads from the throat to the stomach), the stomach, and the intestines are also developing at this time.
In a Bochdalek hernia, the diaphragm may not develop properly, or the intestine may become trapped in the chest cavity as the diaphragm is forming. At times, the tendon that should develop in the middle of the diaphragm does not develop properly. In both cases, normal development of the diaphragm and the digestive tract does not occur.
Diaphragmatic hernia is a multifactorial condition, which means that “many factors,” both genetic and environmental, are involved. It is thought that multiple genes from both parents, as well as a number of environmental factors that scientists do not yet fully understand, contribute to diaphragmatic hernia.
How often does CDH occur?
CDH occurs in about 1 in every 2,500 births. Bochdalek hernias make up about ninety percent of all cases.
Why is CDH of concern?
The lungs are developing at the same time as the diaphragm and the digestive system. A diaphragmatic hernia allows abdominal organs to move into the chest cavity, instead of remaining in the abdomen as they are developing. With the heart, lungs, and abdominal organs all taking up space in the chest cavity, the lungs do not have space to develop properly. This underdevelopment of the lungs is called pulmonary hypoplasia.
A diaphragmatic hernia is a life-threatening illness. When the lungs do not develop properly during pregnancy, it can be difficult for the baby to breathe after birth. Healthy lungs have millions of small air sacs (alveoli), which resemble a balloon filled with air. With pulmonary hypoplasia:
- There are fewer air sacs than normal.
- The air sacs that are present are only able to partially fill with air.
- The air sacs deflate easily due to a lack of a lubricating fluid called surfactant.
When these conditions are present, the baby is unable to take in enough oxygen to stay healthy. The intestines, when relocated in the chest, also may not develop properly, especially if they are not receiving enough blood supply while they are developing. A good blood supply is necessary for the intestines to develop correctly, and to be healthy and function properly.
CDH is also of concern due to possible associated anomalies, which in some cases may include heart, genitourinary, gastrointestinal, central nervous system or chromosomal anomalies.
What if CDH is suspected during pregnancy?
During routine prenatal care at around 18 weeks, an ultrasound may reveal the existence of a diaphragmatic hernia, or what is suspected to be CDH. A more detailed diagnosis, using more sophisticated testing including fetal MRI, is essential to confirm the presence of CDH, and to show more specifically the details of its severity.
What are the symptoms of CDH in babies?
When CDH is not diagnosed prenatally, the symptoms of a Bochdalek diaphragmatic hernia are often observable soon after the baby is born. The following are the most common symptoms of a Bochdalek diaphragmatic hernia. However, each child may experience symptoms differently. Symptoms may include:
- difficulty breathing
- fast breathing
- fast heart rate
- cyanosis (blue color of the skin)
- abnormal chest development, with one side being larger than the other
- abdomen that appears caved in (concave).
A baby born with a Morgagni hernia may or may not show any symptoms. The symptoms of CDH may be similar to other health problems. Please consult your doctor with any concerns.
How is CDH diagnosed after birth?
After birth, your baby’s physician will perform a physical examination. A chest X-ray is done to look at the abnormalities of the lungs, diaphragm, and intestine. A blood test known as an arterial blood gas is often performed to evaluate the baby’s breathing ability. Other tests that may be performed include:
- blood test for chromosomes (to determine if there is a genetic problem)
- ultrasound of the heart (echocardiogram).
Who is at risk for developing CDH?
Parents who have had one child with a diaphragmatic hernia are at increased risk to have another child with the same problem. In cases where it is the only health problem in a baby, the chance for diaphragmatic hernia to happen again in a future pregnancy is 2 percent, or two in 100 chances.
Morgagni hernia is more common in girls than boys, whereas Bochdalek hernia is slightly more common in boys than girls. Babies with the Bochdalek type of diaphragmatic hernia are more likely to have another birth defect. Almost twenty percent have a congenital heart defect. Between 5 to 16 percent have a chromosomal abnormality.
Source: Children’s Hospital of Boston