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Congenital Diaphragmatic Hernia

Congenital diaphragmatic hernia (CDH) is a condition where there is a hole in the diaphragm and organs from the abdomen go up into the chest cavity. CDH was described in 1848 and the first repair in a baby was by Robert Gross in 1946.

Embryology
The diaphragm forms between 4 and 8 weeks of pregnancy and divides the chest from the abdomen. The diaphragm forms from several parts and it is not known for sure why defects or holes occur in the diaphragm. Abnormalities in the diaphragm can be from the different parts failing to meet together or the entire diaphragm can be thin or missing.

Anatomy
The most common type of CDH is to the back and side (“posterolateral”)(Figure 1).

This occurs in about 1 in every 4000 babies. If stillbirths are included, it can occur in up 1 in 2000 births. The hole can vary a lot in size from ½ to 1 inch in size up to complete absence of the diaphragm on one side. Babies who have a large hole in the diaphragm often have problems right after birth and many don’t survive. In general, survival is related to the how small the lung is on the side of the hernia and the opposite side. Most holes in the diaphragm (80%) are on the left side and most of these contain the small intestine, the spleen, stomach, and colon. Right-sided hernias usually contain part of the liver and intestine.

Pathophysiology
Patients with CDH have both small lungs and high blood pressure in the arteries going to the lungs. The intestines and liver that are in the chest during development keep the lungs from growing normally. Also, the lung on the other side of the defect is small. Under the microscope, these lungs look immature as well. While both lungs are small, the lung on the side of the hole can be very small. Also, the arteries to the lung are thicker than normal and this leads very high pressure in the lung arteries. The high pressure in the lungs can cause the blood to back up and go around the lungs. Since this blood is still blue, it can make the baby’s oxygen levels very low. This situation (shunting) can be hard to treat.

Several drugs can be used to try to help this situation. Some drugs (such as nitric oxide) can make the pressure in the lung arteries lower.

Clinical Findings
Many diaphragmatic hernias are discovered before birth on routine prenatal ultrasound (Figure 2). If the liver, stomach, or both are in the chest on prenatal ultrasound, the death rate is somewhat higher. Because most babies with CDH are born with severe breathing problems and often need help right away, these mothers should be cared for in a hospital that can take care of babies with CDH. Because of the lung problems, many babies have severe problems when they are born and have a low oxygen level in the blood. Some babies are born without problems right away and don’t have problems for hours or days, but this is uncommon.

The baby may have a flat abdomen at birth and the heart is pushed to the side opposite from the diaphragmatic hernia. X rays of the baby may show some of the intestine in the chest cavity (Figure 2). These may show the heart shifted to the other side as well. There is another rare lung problem that can look like CDH (cystic adenomatoid malformation), but if there is a question, an upper GI series can show the difference.

Other problems happen in 15% to 25% of babies with CDH, the most common being heart defects. Problems such as holes in the heart (ventricular septal defect), small heart (hypoplastic heart) and others can be seen. Some babies also have chromosome problems, brain problems and others.

Treatment

Before Surgery
All newborns with CDH require surgery; however, the timing of the operation may be different for different babies. In the past, people thought that the babies needed an operation immediately, but it now looks like that is not necessary.

The operation may make the lungs worse because it can put The operation may make the lungs worse because it can put pressure on the good lung. This is usually a problem for just a short time. Before surgery, the baby will usually have a tube going into the stomach and catheters in an artery and vein. The infant will be on a mechanical ventilator and most hospitals will try to keep the amount of pressure on the lungs from the ventilator as low as possible. This is to avoid injuring the very small lungs.

Before surgery, the baby will have a tube in the stomach to keep air out of the intestines and to keep the intestines from pressing on the lungs. The amount of oxygen in the baby’s blood will be watched constantly, usually with a device (pulse oximeter) on the hand or foot. The baby may need medicines to keep the blood pressure normal. In some hospitals, the baby may have a different ventilator that works very fast to breathe for the infant (a high frequency ventilator).

If the baby does not keep the blood oxygen level high enough with these devices, heart lung bypass (ECMO) may be used for several days to weeks. This can only be done in very specialized centers and the infant may be transferred to a center that does ECMO.

The baby will usually have surgery after the situation is stable. It may be days or weeks before an operation is done. If the baby is on ECMO, the infant may have the surgery while on the ECMO machine. The operation may make the lungs worse initially. This is because the intestines are put back into the abdomen and cause pressure on the lungs from below.

Surgical Technique
The CDH is usually fixed by making an incision in the abdomen just below the rib cage. Sometimes, a separate incision in the chest is needed, but if needed, it is usually in babies with a hernia on the right side. The first step is to move the intestines into the abdomen (Figure 4).

After this is done, the edges of the diaphragm are found. If they can be sewn together, they will be (Figures 5, 6, 7). Sometimes, the hole is too large. If this is the case, an artificial patch (such as Gore-Tex) may be used to close the hole (Figure 8 and 9). If, after fixing the hole, there is not enough room in the abdomen for the intestines, another patch may be placed on the abdomen to hold the intestines until the swelling gets better.

The best time for the operation is still debated, but currently most surgeons wait until the baby does not need a lot of help from the ventilator. As mentioned, this can sometimes take days or weeks.

Although appealing, repair of the CDH while the baby is still in the uterus (fetal surgery) has not been shown to be of help. There is still experimental work being done in attempts to grow the lungs in utero, but only in select situations.

There are other experimental projects in babies with CDH including transplanting the lung and using a form of liquid in the lungs to help lung growth. Neither of these is widely available or of proven benefit.

After Surgery
After the operation, the baby will still be on a mechanical ventilator. Depending on how big the hole in the diaphragm is, the baby may need to be on a ventilator for days or weeks. The baby will be started on feedings as soon as the intestines start working, but this may take some time. Also, babies with CDH usually have some form of reflux of stomach contents into the esophagus (GERD) and this may make the feeding more difficult.

Infants with CDH are usually in the hospital for weeks to a few months after the diaphragm is fixed. This mostly depends on how sick the baby is and how small the lungs are. After the baby goes home, they will be followed closely to make sure the hernia doesn’t recur. This can happen quite often, especially in babies with a patch repair of the diaphragm. This is because the baby will be growing, but the patch can’t, so the patch may slowly pull away.

Results

About 2/3 of all babies with CDH who are sick at birth will live. Some of these babies can have other severe problems such as heart defects and many of those babies don’t live. About 80% of infants with CDH and no other problem will live if they are cared for in specialized centers. As mentioned above, these babies do need long-term follow up care as some of them will have other problems.

Other Diaphragm Problems

Foramen of Morgagni Hernia
The foramen of Morgagni hernia (Figure 10) is a hole in the front part of the diaphragm where it connects to the breast bone. This can be in the middle or a little to either side. This is not a common. Patients with these hernias will usually have problems that develop several weeks or months after birth and sometimes much later. The patient will usually have symptoms of intestinal blockage rather than breathing difficulty. Sometimes the hernia is seen on a routine x-ray of the chest.

Surgery can be done through an incision in the upper abdomen or it can also be done using a laparoscope through small incisions. The intestines that are up in the hernia are placed back in the abdomen and the diaphragm is then fixed. Most patients do well after this operation.

Eventration of the Diaphragm
Eventration of the diaphragm is where there is an abnormal elevation of the entire diaphragm or part of it. A person may be born with this (congenital) or it can happen if the nerve to the diaphragm (phrenic nerve) is injured. Congenital Eventration usually is caused by a problem with the muscle of the diaphragm. The diaphragm is very thin in this situation. In acquired eventration, the diaphragm muscle is normal; it is just that the nerve supply is not working. Most congenital eventrations are on left side. The diagnosis is made easily by either x-ray or ultrasound studies.

Babies with eventration are not usually as sick as the baby with a CDH. Many infants with congenital eventration have no symptoms, whereas most children with acquired eventration develop significant symptoms. Children with no symptoms can be watched (Figure 11). Those who have breathing difficulty or who cannot be weaned from a mechanical ventilator require an operation.

The operation to fix an eventration can be done through an incision in the chest or the abdomen. The diaphragm is tightened by removing the very thin areas of the diaphragm and closing the strong areas closer together. Pleats of diaphragm (placation) may be formed. One must be careful to avoid injuring the nerve to the diaphragm.

Paraesophageal Hernia
A paraesophageal hernia is where the stomach slips into the chest cavity along the esophagus. Primary paraesophageal hiatus hernia is a rare problem in children. The children may or may not have symptoms. Vomiting is a common complaint, but sometimes the stomach may get stuck in the chest cavity which requires an emergency operation to correct. The problem is diagnosed with a barium swallow study. Surgery is done through the abdomen. The stomach is placed back in its normal location and the hole is closed. Many of the children also have reflux of stomach contents(GERD) and the surgery to fix that (a fundoplication) is done at the same time.

This problem can occur after a fundoplication as well. It is often noted on a routine chest x-ray. Surgery to fix this depends on the amount of stomach that has slipped into the chest and whether there are symptoms or not.

Adzick NS, Harrison MR, Glick PH, et al: Diaphragmatic hernia in the fetus: Prenatal diagnosis and outcome in 94 cases. J Pediatr Surg 20:357, 1985.
This important study shows the high mortality of infants with CDH diagnosed in utero.

Boloker J, Borteman D, Wung JT, Stolar CJA: Congenital diaphragmatic hernia in 120 infants treated consecutively with permissive hypercapnia, spontaneous respiration and elective repair. J Pediatr Surg 37:357, 2002.
This article describes a pioneering study of a series of neonates with CDH. They were treated primarily with slow, gentle ventilation rather than with ECMO for pulmonary support.

Clark RH, Hardin WD, Hirschl RB, et al: Current surgical management of congenital diaphragmatic hernia: A report from the Congenital Diaphragmatic Hernia Study group. J Pediatr Surg 33:1004, 1998.
A comprehensive review is presented of the current management of CDH based on the combined experience from 62 neonatal centers.

Harrison MR, Keller RL, Hawgood SB, et al. A randomized trial of fetal endoscopic tracheal occlusion for severe fetal congenital diaphragmatic hernia.
N Engl J Med. 349:1916-24, 2003

Articles and graphics adapted from O'Neill: Principles of Pediatric Surgery. © 2003, Elsevier.