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Congenital Diaphragmatic Hernia: From Diagnosis to Delivery and Beyond
Achieving the best outcomes for CDH through interventions before and after birth
Congenital diaphragmatic hernia (CDH) is an extremely challenging prenatal condition that carries with it a relatively high rate of infant mortality. It occurs when abnormal diaphragmatic development allows the abdominal organs to herniate into the fetal chest, interfering with lung development. The abdominal protrusion may also push the heart out of place, impacting the development of the lung on the unaffected side.
The overall incidence of CDH ranges from between 0.8 to 5 per 10,000 births, and its etiology is thought to be multifactorial, likely related to environmental, genetic and nutritional factors.
While advances in prenatal diagnosis, delivery methods, and surgery over the past 20 years has improved the prognosis for infants with CDH, the mortality rate remains high, ranging between 25–30 percent. The primary cause of death is pulmonary hypertension or pulmonary hypoplasia - the underdevelopment of the lungs.
The most common type of CDH (“Bochdalek”), occurring in about 90 percent of cases, is confined to one side of the diaphragm, primarily on the left. Anterior defects, or “Morgagni” hernias, are congenital defects of the anterior part of the diaphragm. Since they do not affect lung development in utero, these are typically not diagnosed during fetal life and patients remain asymptomatic for many years.
This article focuses on the most common type of CDH, which is typically diagnosed prenatally during a routine screening ultrasound in the first or second trimester.
Once CDH is identified on a screening ultrasound, explains Casey Calkins, MD, a pediatric surgeon at The Children's Hospital of Wisconsin, the mother should be referred to a specialized fetal medicine center for confirmatory testing.
At Children's Fetal Concerns Center, clinicians first confirm the diagnosis, then determine the severity of the hernia via ultrasound using the fetal lung-to-head ratio (LHR). The ratio measures the volume of the lung on the opposite side of the hernia and compares it with the head circumference. This provides an estimate of the severity of the CDH by measuring lung hypoplasia, with a lower lung volume predicting a higher risk of morbidity and mortality. Patients with an unfavorable LHR receive a fetal MRI to further corroborate these findings. These tests are all conducted on-site at Children’s, so there is no need to leave the hospital.
“The MRI provides more information about the lung volume,” Dr. Calkins says. “This allows us to offer patient-specific counseling to families about what to expect after delivery.” The MRI also allows clinicians to look for other anomalies common in these patients, check the location of the liver, and better assess the growth of the lung. All directly impact prognosis after birth.
According to Dr. Calkins, in some circumstances the MRI may identify those eligible for fetal surgery. Patients eligible for surgery may be referred to one of four centers in the country that currently offer fetoscopic endoluminal tracheal occlusion (FETO), in which a balloon is inserted into the trachea to encourage lung growth.
All patients who are diagnosed with CDH also undergo a fetal MRI to determine if there are any significant structural abnormalities of the heart. The presence of heart defects is more common in patients with CDH, and may impact prenatal counseling.
Delivery and Post-Natal Care
Once CDH is diagnosed, it is important to refer the mother to a center like the Fetal Concerns Center so care can be established and the baby can be delivered there. “We feel that transporting a baby with CDH - even just down the street - creates unnecessary stress, and we want to eliminate the amount of stress on the newborn infant with this condition,” says Dr. Calkins.
The majority of babies with CDH are delivered vaginally, with a multidisciplinary team composed of maternal-fetal medicine specialists, neonatologists, surgeons, respiratory therapists and others waiting. The immediate priority is to stabilize the infant and provide respiratory support with intubation. Once stabilized, clinicians focus on cardiorespiratory support, particularly given the high rate of pulmonary hypertension these infants experience.
ECMO and CDH
The most commonly used intervention in patients with heart and lung problems is extracorporeal membrane oxygenation (ECMO), with some centers putting up to 40 percent of their patients on the heart/lung machine. Indeed, CDH is one of the most common indications for its use. There is wide variability in its use across centers, however, with those that rarely use it still demonstrating good survival rates.
The Fetal Concerns Center’s ECMO rate is extremely low, yet its 78 percent survival rate compares favorably to other specialized centers that use it more often. “The low rate could be due to selection bias or even luck,” Dr. Calkins says, “but it is most likely related to clinical persistence with non-ECMO interventions.”
Children’s tries to “avoid the early trigger to place a CDH patient on ECMO without maximizing all other treatment modalities,” he says, “because it is an intervention with its own set of complications.”
Two large IV cannulas are placed in the artery and vein in the infant’s neck to divert blood away from the affected lungs into a machine that removes carbon dioxide and provides oxygen. This allows time for the infant’s heart and lungs to rest. The use of ECMO may, however, increase the risk of long-term neurodevelopmental delay. In addition, the infant must receive heparin to reduce the risk of clotting, which increases the risk of intracranial hemorrhage. Finally, ECMO is expensive and labor intensive, and it may preclude additional interventions while the infant is on the machine. Thus, says Dr. Calkins, “It is important to pursue all avenues of cardiopulmonary support prior to using ECMO.”
However, if ECMO is required, “we have what I believe to be one of the best ECMO support teams in the country,” Dr. Calkins says. The team is trained to have the baby on the machine in as little as 30 minutes.
Surgery Comes Later
“Forty years ago, it was believed that the key to survival in infants with CDH was immediate surgery to repair the diaphragm,” Dr. Calkins says. Today, however, it is understood that the most important thing is to treat the PH and support the baby through the initial postnatal period, then repair the defect once the heart and lungs stabilize. At Children’s, 10 pediatric surgeons skilled in CDH repair are available, all with extensive experience with minimally invasive repair if the child is a suitable candidate.
According to Dr. Calkins, congenital heart disease is often found in babies with CDH, providing another advantage to delivery at Children’s. “We have one of the best congenital heart programs in the country,” he says.
The Fetal Concerns Center is also involved with the Institute of Health’s DHREAMS (Diaphragmatic Hernia Research & Exploration; Advancing Molecular Science) study. Investigators at medical centers throughout the country are enrolling individuals and families with CDH in the study to better understand the molecular basis of the condition. The goal is to reach a better understanding of the cause of CDH, leading to significant advances in the diagnosis, prognosis, prevention and treatment of this disease.
1. Chandrasekharan PK, Rawat M, Madappa R, Rothstein DH, Lakshminrusimha S. Congenital Diaphragmatic hernia — a review. Matern Health Neonatol Perinatol 2017;3:6.
2. Kays DW. ECMO in CDH: Is there a role? Semin Pediatr Surg. 2017;26:166-70.
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