The Fetal Treatment Program
HASBRO CHILDREN'S HOSPITAL - WOMEN & INFANTS' HOSPITAL OF RHODE ISLAND
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WHAT IS CONGENITAL DIAPHRAGMATIC HERNIA (CDH)? Congenital diaphragmatic hernia (CDH) refers to a defect in the diaphragm that allows the abdominal organs (stomach, intestine, liver, spleen) to move into the chest cavity. Congenital diaphragmatic hernia can occur on either the left or the right side but is most common on the left. WHY WORRY ABOUT DIAPHRAGMATIC HERNIA? Babies who have CDH suffer from small and underdeveloped lungs. This is termed pulmonary hypoplasia. CDH allows the intestines to move up into the chest cavity. It is believed that this prevents the heart and the lungs from developing properly (figures 1 and 2). CDH is a life-threatening illness. When the lungs of a baby do not develop properly during pregnancy it can be difficult for the baby to breathe after delivery. The lungs of babies born with CDH are hypoplastic. The alveoli that are present are much more fragile and are missing surfactant. In comparison, normal lungs at birth have millions of small alveoli, which can best be thought of as many, many clusters of grapes. When babies are born with CDH and hypoplastic lungs, there are not enough alveoli to get oxygen in the blood, or to get rid of carbon dioxide from the body. When this occurs, the lack of oxygen leads to severe illness requiring very aggressive supportive measures.  Figure 1: Normal chest anatomy  Figure 2: Congenital diaphragmatic hernia. Intestinal loops are in the left chest (on the right in the picture). This pushes the heart toward the right lung, and compresses the left lung, which does not develop normally. The right lung is compressed as well. Another reason why CDH is of concern is because of the possibility of having other associated birth defects (anomalies) that may impact on the baby's survival. In some cases the heart may have defects. The gastrointestinal tract, (the esophagus, stomach and intestines) may be malfunctioning because they developed in the chest, rather than in the abdomen. Kidney and central nervous system defects are also known to occur in babies with CDH. Finally, chromosomal defects (most commonly trisomy 21, 18, and 13) are found in approximately 10-30 percent of babies with CDH. |
PRENATAL
TREATMENT FOR DIAPHRAGMATIC HERNIA
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WHAT IS CONGENITAL DIAPHRAGMATIC HERNIA (CDH)? Congenital diaphragmatic hernia (CDH) refers to a defect in the diaphragm that allows the abdominal organs (stomach, intestine, liver, spleen) to move into the chest cavity. Congenital diaphragmatic hernia can occur on either the left or the right side but is most common on the left. WHY WORRY ABOUT DIAPHRAGMATIC HERNIA? Babies who have CDH suffer from small and underdeveloped lungs. This is termed pulmonary hypoplasia. CDH allows the intestines to move up into the chest cavity. It is believed that this prevents the heart and the lungs from developing properly (figures 1 and 2). CDH is a life-threatening illness. When the lungs of a baby do not develop properly during pregnancy it can be difficult for the baby to breathe after delivery. The lungs of babies born with CDH are hypoplastic. The alveoli that are present are much more fragile and are missing surfactant. In comparison, normal lungs at birth have millions of small alveoli, which can best be thought of as many, many clusters of grapes. When babies are born with CDH and hypoplastic lungs, there are not enough alveoli to get oxygen in the blood, or to get rid of carbon dioxide from the body. When this occurs, the lack of oxygen leads to severe illness requiring very aggressive supportive measures.
CDH occurs approximately in 1 of 2,500 births and can be usually detected before birth. The specific cause of CDH is unknown but is most likely multifactorial in origin. While certain drugs or environmental exposures have been questioned, no specific agent has ever been identified. Many parents are concerned that it was something genetic that they passed on to their baby; however, fewer than 2 percent of CDH cases are believed to be familial. Most cases of congenital diaphragmatic hernia and pulmonary hypoplasia are sporadic and isolated events. Research into the cause and treatment of diaphragmatic hernia is being performed in a number of centers around the country and around the world, including our own. Our laboratory is actively involved in trying to understand the mechanisms involved in normal and abnormal lung growth. All these efforts may ultimately help find a cure for this condition. Additionally, our Fetal Treatment Program is actively involved in counseling parents about prenatal options and helping to plan delivery and treatment of the baby after birth. The most common type of CDH is a hole in the back of the diaphragm, also called Bochdalek hernia. The left side is affected approximately 85 percent of the time. This type of hernia is the gravest type, and the left chest usually contains the stomach, intestines, part of the liver and the spleen. This causes severe pulmonary hypoplasia of the left lung and significant hypoplasia of the right lung as well. When it occurs on the right side of the diaphragm, a significant amount of liver may end up in the right chest, causing right lung hypoplasia and affecting the function of the heart. A second type of diaphragmatic hernia is called the Morgagni hernia. This is a less common defect that involves a hole in the front portion of the diaphragm, just behind the sternum. Sometimes the intestines or a piece of liver may move up through this defect in between the heart and the sternum, but this usually does not cause pulmonary hypoplasia. I AM TOLD MY FETUS HAS DIAPHRAGMATIC HERNIA - NOW WHAT? Prenatal diagnosis is important
in that it allows for patient/parent education, identification
of those babies at risk for the worst outcome and the opportunity
to provide prenatal intervention if possible.
FETAL INTERVENTION AT THE FETAL TREATMENT PROGRAM
The first attempts at fetal surgery for CDH date back to the 1980's, when large animal experiments of open fetal surgery were developed. In the 1990's the first human cases of open fetal surgery were attempted and reported in the New England Journal of Medicine. The initial results of the prenatal therapy to repair the underdeveloped lungs were not as good as expected, because of the extreme aggressiveness of this type of operation on the mother and the baby. Since, in the mean time, treatment after birth became more successful, "open" fetal surgery for CDH was abandoned. Techniques of correcting these defects inside the uterus have evolved as well, however. Open fetal surgery for CDH has been replaced by fetal tracheal occlusion. Experimentally, this has been shown to result in accelerated growth of the hypoplastic lungs. Our laboratory, as well as others,' have been very active in the last decade to further understanding the mechanisms involved in this accelerated lung growth following fetal tracheal occlusion. Fetal intervention for CDH continues to evolve. Performance of occlusion can be performed through a single entry port technique. This technique (developed at our institution) allows occlusion of the fetal trachea with an inflatable and detachable balloon. Most recently, a multicentric study performed in Europe (Eurofoetus) has compared treatment for CDH with the single port technique to standard treatment after delivery. These results were very informative and encouraging. It may be possible to identify a specific subgroup of babies with CDH in whom the survival can be predicted to be less than 10-40 percent despite all the current methods of postnatal therapy (including ECMO, gentle ventilation strategies, permissive hypercapnia, nitric oxide). In this group of severe CDH, fetal endoscopic tracheal occlusion increased this survival to 50-80 percent (Eurofoetus study). Fetal tracheal occlusion resulted in an increase in the lung growth based on follow up prenatal ultrasound measurements of the lung-to-head ratio (LHR) CURRENT RATIONALE FOR PRENATAL TREATMENT OF SEVERE CDH Currently the majority of babies with CDH are best treated after birth. The choice of therapy is in part dictated by the presence or absence of known predictive factors. These include the gestational age at initial diagnosis (less than 25 weeks is a poor prognostic indicator), the presence of part of the liver in the chest ( poor indicator), the presence of polyhydramnios (too much amniotic fluid), presence of the stomach into the chest and the lung-to-head ratio ( LHR), which is one of the more reliable indicators of prognosis. Another indicator is the observed/expected lung volume (O/E), also expressed as the percentage predicted lung volume (PPLV): based on MRI images of the fetal chest cavity, it is possible to predict how large the lungs should be, and how large they actually are. The difference between these two values is the O/E, or PPLV. For the most severe cases of
CDH, extracorporeal
membrane oxygenation (ECMO) is likely to be required. ECMO
is a lung bypass machine that allows for gas exchange while the
baby's lungs are resting and maturing. In the babies with the
worst cases of pulmonary hypoplasia, however, ECMO can only be used for a few weeks and
does not allow enough time for the lungs to grow or mature to
live. Additionally, ECMO
caries significant risks including long term damage to the lung,
brain and other organs. Based on all the available literature,
including reports on experimental pulmonary hypoplasia and tracheal occlusion as well as our own experience
with experimental and clinical fetal surgery, the Fetal Treatment
Program at Brown/ Hasbro/Women & Infants has developed a
management plan for severe CDH. This treatment option is offered on a case by case basis, and only after extensive discussion with parents, referring physician, local experts and the multidisciplinary antenatal diagnosis and management (MADAM) board of our Fetal Treatment Program. It is our belief that the babies with highest risk diaphragmatic hernia, where the chances of survival is estimated at less than 10-40 percent, endoscopic fetal tracheal occlusion will allow accelerated lung growth to occur enough that it will convert the severe condition into a condition with intermediate or good prognosis, and a predicted survival greater than 50-65 percent.
If the diagnosis is not known
prenatally, the baby will develop signs suggesting a diaphragmatic
hernia. This usually includes difficulty breathing with a very
fast breathing rate, a very high heart rate and hypoxia (not
enough oxygen in the blood) and cyanosis (a blueish color of
the skin, caused by a lack of oxygen). The baby will be treated
by our expert team of CDH specialists, which includes a pediatric
surgeon and a neonatologist in the neonatal intensive care unit
(NICU). After surgery the baby will be kept in the neonatal intensive care unit until full recovery. Many babies will require ventilator assistance for a number of days to weeks after surgery, until the lung has time to recover and improve its function. The future for babies with diaphragmatic hernia is improving. The outcome for these babies is primarily based on the degree of lung underdevelopment and prevention of injury to those fragile lungs at birth. All babies will require a strict follow-up with the pediatric surgical service, to assist the long-term management of problems that may be part of the condition. Many babies may have problems requiring medications for lung therapy. Other babies have feeding problems from the malpositioned stomach in the chest during development that leads to difficulty eating and with weight gain. Gastroesophageal reflux is one such condition. Many times babies require additional feedings through the placement of a feeding tube to give more calories in order to grow and become healthier. This detailed follow up also provides the opportunity to ensure proper development. Early problems identified during follow up with feeding, growth, or failure to meet normal milestones, are treated early. Early intervention with speech therapy and occupational therapy often help these babies improve muscle strength and coordination. Although this requires a lot of work, with this established teamwork, the overall outlook for babies born with CDH and pulmonary hypoplasia is often bright.
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