GUEST CORNER

Diaphragmatic Hernia

Cynthia Curry, M.D.

Introduction and epidemiology. Approximately 1 in 3,000 liveborn infants has a diaphragmatic hernia. Even this number may underestimate the number of babies afflicted with this birth defect, since many infants are stillborn and then may not have the appropriate pathologic studies completed to determine the cause of death (see Editorial Comment below). Diaphragmatic hernias are more common in twins. There is no known association with a mother’s age, ethnic background or number of pregnancies.

Embryologic development. The diaphragm separates the abdominal organs from the lungs and heart leaving openings for the major arteries and veins and for the esophagus. The development of the diaphragm is an extremely complex event and remains incompletely understood. It spans the period from 22 days post conception through the eighth week of development. There are three distinct components which are involved in the development of the diaphragm. All of these migrate from the periphery to the midline, eventually resulting in the closure of the openings called the pleuroperitoneal canals on either side of the midline.

That multiple components are involved in diaphragmatic development helps explain why there are various anatomic forms of diaphragmatic hernias (depending upon what element is abnormal and in what way that abnormality is manifested). The most common form of diaphragmatic hernia involves a failure of the left pleuroperitoneal canal to close. In contrast, complete absence of the diaphragm is quite rare, accounting for less than 1% of all diaphragmatic defects. A particularly mild form of diaphragmatic hernia, called a Morgagni hernia, is often diagnosed in somewhat older infants; this particular form arises more frequently in children with Down syndrome.

Impact of prenatal diagnosis. Increased routine utilization of prenatal ultrasonography has led to recognition of diaphragmatic hernia as early as 15 weeks gestation. Nonetheless the prenatal diagnosis of this defect can be challenging even for experienced ultrasonographers, particularly because other congenital lung lesions can cause diagnostic uncertainty.

When a diaphragmatic hernia is suspected, additional diagnostic steps are indicated in order to give the family and their physicians as much information as possible upon which reasoned decisions and plans for management can be based. More than half of infants with diaphragmatic hernia have other anomalies. These additional birth defects encompass a wide range of problems and of severity, most frequently involving the development of the heart and somewhat less frequently the limbs, the central nervous system and the kidneys. Careful ultrasound examination of the fetal heart, limbs, brain, etc. may help determine if this is an isolated diaphragmatic hernia or if it is part of a multiple congenital anomalies syndrome. Chromosomal abnormalities are present in at least 5% of liveborn infants with diaphragmatic hernia. Therefore, the physician managing any patient with this suspected diagnosis will virtually always recommend amniocentesis or fetal blood sampling in order to assess for the presence of a chromosome abnormality.

Infants with isolated, non-syndromic diaphragmatic hernia have a greater probability of surviving. Problematically, even with high level ultrasound and cytogenetic assessments, a baby may have other severe anomalies which remain undetected prior to birth.

Survival and intervention. With the prenatal diagnosis of diaphragmatic hernia families will be told that their baby faces formidable odds. About 50% of infants with diaphragmatic hernia will die even if the most aggressive and advance management methods are undertaken. Given such odds, some families may elect to terminate a pregnancy in which a diaphragmatic hernia is diagnosed in the second trimester. Others may try to maximize the chances for survival, sometimes by undertaking heroic measures — including fetal surgery.

Pediatric surgeons have been dismayed and disheartened by the low survival rate and high frequency of complications encountered in infants with a diaphragmatic hernia. Attempts have been made to intervene prior to birth in order to try to prevent some of the complications which arise in the newborn period. Several novel approaches have been tried.

Dr. Michael Harrison, at the University of California in San Francisco, has performed fetal repairs at about 24 weeks gestation on several infants with diaphragmatic hernias. This procedure involves opening the mother’s uterus, controlling the loss of amniotic fluid, and operating on the externalized fetus with the placement of a Gortex patch in the fetal diaphragm. It is thought that such surgery should allow for more normal fetal lung development and, so, would improve survival chances. There have been at least two survivors of this intrauterine surgery, but the risks of premature labor and of fetal death remain extremely high.

Recently efforts have explored the possible efficacy of plugging the trachea of the affected fetus (with material which acts like a ‘cork’ and which can be removed prior to the infant’s first breath). Many babies with diaphragmatic hernia die because in the presence of this defect lung growth is insufficient to sustain life after delivery. Studies in experimental animals have recently shown that lung growth is enhanced by such tracheal blockage, even in the presence of a diaphragmatic hernia. This approach is less stressful than attempting complete surgical repair and is a technique sure to undergo further development and testing in the next few years.

Other surgeons have attempted to solve the problem of lung hypoplasia through creation of an artificial opening in the abdominal wall and allowing the intestinal organs previously located in the chest to develop outside of the fetal body, in the amniotic cavity. While of limited utility, this approach may be the best alternative in rare instances.

Clearly, much remains to be learned about the role of in utero surgery in the management of this defect.

More conventional intervention measures include plans to deliver the mother in a high risk, tertiary care center with the optimal environment needed to resuscitate and stabilize the infant, manage the surgery and handle the ventilation demands of these babies who uniformly have underdeveloped lungs. The role of extracorporeal membrane oxygenation (ECMO) in the treatment of these infants remains controversial, with marked enthusiasm in some centers and a less optimistic appraisal of fetal outcome in others.

Recurrence risks. For families who have had a liveborn or stillborn infant with diaphragmatic hernia, many questions need to be addressed. Was this an isolated defect or were there multiple anomalies? Was there a recognizable syndrome? Was there a chromosomal abnormality? Involvement of a medical geneticist can help sort out what are often complicated clinical diagnostic dilemmas: There are at least 20 recognized multiple malformation syndromes and more than 10 chromosomal abnormalities known to be associated with diaphragmatic hernia. Each of the syndromes are individually quite rare, but when present each carries with it a specific risk for recurrence for the parents. Therefore, recognition of such syndromes is essential in providing parents with information upon which to base future reproductive decisions.

When isolated (and especially when it is of the common type) recurrence risk for diaphragmatic hernia is low and families can be generally reassured. Prenatal monitoring in subsequent pregnancies by experienced ultrasonographers is appropriate for any family in which there has been a previous child with diaphragmatic hernia. In the majority of instances families will be reassured by this prenatal monitoring.

We have much to learn regarding the causes, treatment and prevention of diaphragmatic hernia. Although the overall outlook is likely to remain poor, for selected infants the potential for new in utero surgical techniques is exciting.

Further reading:
Cunniff C, Jones KL, Jones MC (1990) Patterns of malformation in children with congenital diaphragmatic hernia. J Pediatr 116:258-261.

Ford WD (1994) Fetal intervention for congenital diaphragmatic hernia. Fetal diagn therapy 9:398-408.

Harrison MR, Adzick NS, Estes JM, Howell L (1994) A prospective study of the outcome for fetuses with diaphragmatic hernia. JAMA 271:382-384.

Torfs CP, Curry CJR, Bateson TF, Honore LH (1992) A population-based study of congenital diaphragmatic hernia. Teratology 46:555-565.

Puri P (1994) Congenital diaphragmatic hernia. Current problems surg 31:787-846.

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Editorial Comment
Because of Dr. Curry’s article, I searched the WiSSP database in order to provide information concerning diaphragmatic hernia in infants who are stillborn. Through October 1, 1376 referrals have been assessed and entered into our database. Of these, 18 (1.3%) were found to have a diaphragmatic hernia. Within this group there were 12 infants who were stillborn and 6 who died in the immediate newborn period. This then means that 12 of 1077 stillborn infants (1.1%) were found to have a diaphragmatic hernia; since this is a non-biased sample of babies dying in utero, we can conclude that about 1% of all stillborns have a diaphragmatic defect. This also allows for a rough calculation of the proportion of infants with diaphragmatic hernia who die in utero. If the frequency of diaphragmatic hernia in liveborns is 1/3000; and the frequency of diaphragmatic hernia in stillborns is 1/100; and the ratio of stillbirth to livebirth is 1:115, then about 1 in every 4 infants with diaphragmatic hernia is stillborn.

Not surprisingly, the proportion of those with multiple anomalies is even greater than in the liveborn population, with 10 of 12 stillborn infants with diaphragmatic hernia having a multiple congenital anomalies syndrome. Diagnoses made in the group as a whole and in stillborns only include:

Note that in our population by far the most common diagnosis associated with diaphragm abnormalities is trisomy 18.

RMP