What Is a Congenital Diaphragmatic Hernia (CDH)?

A congenital diaphragmatic hernia (CDH) is a defect in the diaphragm occurring during embryologic development that results in herniation of the abdominal contents into the chest. This leads to the compression of the lungs and abnormal pulmonary vascular development. The diaphragm normally develops in the first trimester, with the right diaphragm closing before the left. The organs that are typically found herniated into the thoracic cavity are the stomach, intestines, spleen, and/or liver (Figure 22.1). There are two common types of diaphragmatic hernias: Bochdalek and Morgagni. The Bochdalek hernia occurs on the posterior-lateral portion of the diaphragm, and the Morgagni hernia on the anterior aspect. These hernias can be right-sided, left-sided (most common), or bilateral.

Figure 22.1 Chest X-ray demonstrating a large right-sided congenital diaphragmatic hernia with herniation of the bowel into the right hemithorax. The right lung markings are absent and the trachea is deviated leftwards.

Courtesy of Adam C. Adler MD

The incidence of CDH has been reported to be between 1-in-2000 and 1-in-5000 live births.

Describe the Pathophysiology of CDH

CDH results in pulmonary hypoplasia from compression of the fetal lungs during development. Pulmonary vascular hyper-reactivity, or persistent pulmonary hypertension may also occur. Hypoxia, hypercapnia, respiratory acidosis, and hypothermia contribute to worsening pulmonary hypertension and persistence of the fetal circulation. This will lead to right-to-left shunting across a patent ductus arteriosus.

How Is the Diagnosis of CDH Made?

CDH is most commonly diagnosed with prenatal ultrasound, usually in the second or third trimester. However, fetal magnetic resonance imaging may also be used. The abdominal contents can be observed in the fetal chest on imaging. Ultrasound Doppler examination of the hepatic and umbilical vessels can aid in diagnosis. Echocardiography and genetic testing may be performed to exclude co-existing anatomic anomalies and syndromic associations.

Early diagnosis allows for counseling, coordination of delivery at a specialized tertiary center, and consideration of elective termination if desired by the family.

What Is the Differential Diagnosis for CDH?

Other diagnoses to be considered in suspected CDH include diaphragm eventration, teratoma, bronchogenic or enteric cysts, and congenital cystic adenomatoid malformation.

How Is the Prognosis Determined?

Prognosis in CDH is determined by prenatal lung volume-based prognostication. The lung-to-head (LHR) ratio is most commonly used. Another method used is percent predicted lung volume (PPLV).

The presence and extent of liver herniation, or concomitant major anomalies, is indicative of poor prognosis.

Presence of liver herniation correlates with the need for extracorporeal membrane oxygenation (ECMO) support. Greater than 80% of patients with liver herniation into the thorax require ECMO support compared with 25% of patients without liver herniation.

What Is the Lung-to-Head Ratio (LHR)?

The LHR is calculated by measuring the lung area (on the contralateral side of the hernia) using ultrasound, and then dividing the number by the head circumference. A value less than 0.9 denotes a low rate of survival, whereas above 1.4 favors survival.

What Is Percent Predicted Lung Volume (PPLV)?

The PPLV is calculated by taking the total measured thoracic volume, and subtracting the measured mediastinal volume from this value. These measurements are based on fetal magnetic resonance imaging. A value of 15 or less denotes high risk of pulmonary morbidity and/or death.